Development of a High-Throughput Screening Method for Oxide-Ion

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Development of a High-Throughput Screening Method for Oxide-Ion Conductors and Its Application to Bismuth-Based Oxide Library Thin Films Masato Matsubara, Akitoshi Suzumura, Shin Tajima, and Ryoji Asahi ACS Comb. Sci., Just Accepted Manuscript • DOI: 10.1021/acscombsci.8b00193 • Publication Date (Web): 07 Mar 2019 Downloaded from http://pubs.acs.org on March 18, 2019

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ACS Combinatorial Science

Development of a High-Throughput Screening Method for Oxide-Ion Conductors and Its Application to Bismuth-Based Oxide Library Thin Films Masato Matsubara,* Akitoshi Suzumura, Shin Tajima, and Ryoji Asahi Toyota Central R&D Laboratories, Inc., Nagakute, Aichi 480-1192, Japan KEYWORDS: combinatorial synthesis, high-throughput characterization, ionic conductor, ferroelectrics, bismuth oxide ABSTRACT: To accelerate material discovery, we develop a screening method for oxide-ion conductors that comprises combinatorial synthesis using chemical-solution deposition, and highthroughput measurements using x-ray diffraction and conductivity. The present method allows us to form an arbitrary and uniform composition within an evaluation area at an arbitrary position in the library on a substrate. This screening method is applied to ABi2Zrx(Nb1−yTay)1−xO9 bismuthlayered compounds, which are known to have relatively high oxide-ion conductivities but are yet to be examined thoroughly. By making systematic thin-film libraries for A=Sr or Ca, we aim to find the optimized composition. The total time required for synthesis, phase identification, and conductivity measurements is found to be significantly shorter than that with the conventional

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method, and the maximum oxide-ion conductivity of this compound in the libraries reaches 10−3 S/cm at 800° C.


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INTRODUCTION Oxide-ion conductors (OICs) are used in various electrochemical devices, such as solid oxide fuel cells (SOFCs), oxygen separation membranes, and sensors.1–3 In particular, SOFCs have attracted attention as a highly efficient and safe power-generation technology that could solve environmental energy problems. Currently, yttria-stabilized zirconia (YSZ) is used as a practical material for SOFCs. However, a YSZ-based SOFC requires temperatures in excess of 800° C to achieve high conductivity,4 but such high temperatures could degrade those parts of the SOFC that contain solid electrolytes. Meanwhile, at low temperatures the cell performance deteriorates because of the high ohmic resistance of YSZ. Therefore, instead of YSZ, materials must be developed that possess both chemical stability and ionic conductivity at lower temperatures. Over time, various novel OICs with high conductivity at low temperatures have been studied by traditional methods,5–10 but many of them have drawbacks, such as low ionic conductivity and instability at high temperatures. Generally, a considerable amount of processing time is required to develop new materials, involving sample synthesis, quality evaluation, and the measurement of physical properties. Therefore, to find superior materials in less time, the search process must be accelerated. Highthroughput (HT) technology comprises (i) combinatorial chemistry that systematically synthesizes many samples whose compositions have changed continuously and (ii) HT evaluations that measure material properties quickly. For organic materials, HT technology has been used to discover new drugs in the pharmaceutical field.11 For the decade, this method has also been applied to various functional inorganic materials, such as semiconductors,12 dielectrics,13 optical materials,14 and catalysis,15 and has attracted attention as an efficient method for materials research.16


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Herein, we use HT technology to search for novel OICs. Several technical problems must be overcome before HT technology can be applied to inorganic functional materials. First, ionconductor library films should have sufficient thickness more than 1 μm to measure the resistance accurately. Therefore, in the present study, the library films are prepared by chemical solution deposition (CSD), which easily creates thick films with various compositions . Second, it is important to be able to identify the phase of each library film quickly. To date, several HT xray diffraction (XRD) methods have been proposed for analyzing the crystal structure of library films.17,18 Likewise, we use powerful synchrotron radiation with a two-dimensional detector (PILATUS) at the synchrotron radiation facility (SPring-8, Hyogo, Japan) to determine phases quickly. Third, it is important to develop an HT system for measuring physical properties that is suitable for the target functional materials, this being a potential bottleneck process in materials development. Noncontact spectroscopy can be used for HT evaluation of the electrical conductivities of metallic materials.19 However, to evaluate ionic conductivity accurately, a probe must come directly into contact with the film to analyze the impedance properties of the latter.20 Herein, we design a probe-scanning contact-type HT conductivity-measurement system and use it to screen OICs. Among OICs, bismuth oxide has been known to possess high ionic conductivity exceeding that of YSZ21 while being chemically unstable because of its high volatility and reducibility. As well as simple bismuth oxide, bismuth-based complex oxides such as Bi2VO5.5 are also recognized as good ionic conductors22 even though they have low chemical stability. Meanwhile, the bismuthbased oxide (Bi0.5Na0.5)TiO3 (BNT), which has been studied as a lead-free piezoelectric material,23 was shown to have high ionic conductivity equivalent to that of YSZ at 600° C, thereby attracting attention.24 In the literature, it was pointed out that localized Bi3+ loosely


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hybridized with O2− and the lattice softening that is accompanied by displacement of cations and anions during the ferroelectric phase transition are advantageous for not only ferroelectricity but also oxide-ion conduction.24 In addition to BNT, tungsten–bronze ferroelectric compounds also exhibit ionic conductivity of 6×10-4 S/cm at 600° C.25 Very recently, bismuth-layered compounds such as SrBi2Ta2O9, SrBi2Nb2O9, BaBi2Nb2O9, and CaBi2Ta2O9 have been proposed as good OICs through virtual screening, using a newly developed ensemble-scope descriptor.26 Bismuth-layered compounds have the general formula (Bi2O2)2+(Am−1BmO3

2− m+1)

and are ferroelectrics with various compositions depending on the

stacking number m of (Bi2O2)2+ blocks and the types of cations A and B.27–29 Many of these compounds have rarely been studied as OICs until now. However, as part of a dielectric investigation, the conductivities of the bismuth-layered compounds SrBi2Ti2O5 (SBT), SrBi2Nb2O9 (SBN), and SrBi4Ti4O15 (SBIT) have been reported,30–32 of which SBIT is a mixed conductor30 and SBT has the potential for high oxide-ion conductivity by adding acceptor dopants.31,32 Despite the aforementioned interest in bismuth-layered compounds, how composition influences conductivity has yet to be studied sufficiently. Therefore, using an HT screening method developed for OICs, library films of the system AZrx(Nb1−yTay)2−xBi2+zO9−δ (A = Sr or Ca) are investigated systematically herein to find the best composition in the libraries. We then show that the results do indeed demonstrate that this approach is effective.


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EXPERIMENTAL PROCEDURES Fabrication of Library Films. We fabricated 36 compositional library films (six rows and six columns) on an alumina substrate and examined the combination of elements among the different stoichiometric compositions. The composition of a bismuth-layered compound is AZrx(Nb1−yTay)2−xBi2+zO9− δ, and we examined (i) the type of alkaline earth ion of the A site, (ii) the Zr content x as an acceptor dopant for introducing oxygen deficiency, (iii) the Ta content y, and (iv) the excess Bi content z regarding Bi volatilization during the sintering process. The metal organic solutions of each of the raw materials of bismuth oxide (BI05; Kojundo Chemistry Co., Ltd., Japan), calcium oxide (CA03; Kojundo Chemistry Co.), strontium oxide (SR06; Kojundo Chemistry Co.), niobium oxide (NB05; Kojundo Chemistry Co.), tantalum oxide (BI10-P; Kojundo Chemistry Co.), and zirconium oxide (ZR05-P; Kojundo Chemistry Co.) with butyl acetate (guaranteed reagent; FUJIFILM Wako Pure Chemical Corp., Japan) as a solvent were poured into separate sample bottles and set on the reservoir base of an automatic pipetting device (SM300DSZ; Musashi Engineering Co., Ltd., Japan). Each solution, the weighed value of which was programmed beforehand, was dispensed automatically onto a microplate set in the automatic pipetting device so that the total concentration was 0.05 M and each element had the desired ratio. The microplate was then set in a vibration mixer and agitated for 60 minutes to form a homogeneous precursor solution. An alumina substrate with dimensions of 30 × 30 × 1 mm was used and a stainless-steel mask was attached with adhesive to the alumina substrate. The mask contained 36 square holes, each 3 × 3 mm in size and arranged at regular intervals. Of the precursor solution, 0.1 μL was dropped onto the alumina substrate through the holes to form the library films. After drying the solution at 120° C for five minutes, the mask was peeled off and then sintered at 600° C for 30 minutes.


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The same process was repeated six times to achieve a final film thickness in excess of 1 μm. The final sintering temperature was optimized by annealing the films at 600–1,000° C for 30 minutes to densify the library films. Compared to the libraries of continuously varying composition typically prepared by sputtering, the present method allows us to form an arbitrary and uniform composition within an evaluation area at an arbitrary position in the library. This feature is important for ensuring that the composition or phase corresponds to the physical properties evaluated for a certain dimension (the probe distance in the present case), which could differ from that used for the phase determination (typically the beam size of XRD). In addition, it may be convenient to make libraries of discontinuously varying composition for employing a fast optimization algorithm, such as Bayesian optimization, to find the best composition with a minimum number of libraries. As standard samples to confirm the performance of the HT measurement system, three 8%YSZ (8YSZ) samples were prepared, namely, a sputtered thin film, a sheet-sintered body, and a bulk-sintered body. The 8YSZ sputtered thin films were prepared by sputtering on an alumina substrate of size 30 × 30 × 1 mm and annealed at 950° C for one hour after sputtering. The bulksintered body was prepared by uniaxially press molding commercially available 8YSZ powder (TZ-8Y; Tosoh Co., Ltd., Japan) in a disk shape at 100 MPa and sintering it at 1,400°C for ten hours. A green sheet of the same powder was also sintered at 1,440° C for one hour to prepare a sheet-sintered body. To evaluate the oxide-ion transport number, bulk samples of the typical bismuth-layered compounds SrBi2Ta2O9, SrBi2Nb2O9, CaBi2Nb2O9, and Ca2Bi2Ta2O9 were also prepared by the solid-state reaction method. Each raw-material powder was weighed as a desired ratio and mixed for 24 hours in a ball mill. The mixture was then calcined at 900° C for ten hours and molded in


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a disc shape after ball milling under the same conditions as above. The calcined powders were sintered at 1,150° C for one hour. A concentration cell for measuring the transport number was prepared by the following procedure.33 A sintered sample was set between two quartz tubes and fixed with a spring. Nitrogen and oxygen flowed from both ends of the quartz tube, respectively, and the electromotive force was measured at 700 °C in an electric furnace. The oxygen partial pressure was determined as 1 atm on the oxygen flow side and 46 ppm on the nitrogen flow side by using a YSZ standard sample. HT measurement methods. To identify the phase of each library thin film, synchrotron radiation at the SPring-8 facility was used. The system settings are shown in Fig. 1. The library film was attached to a sample holder equipped with an XY stage. XRD data of the entire composition of the library film were obtained rapidly by irradiating x-rays with a wavelength of 0.8 Å (15.5 keV) while scanning the XY stage and detecting the diffracted light with a twodimensional detector (PILATUS). The thickness of each library thin film on an alumina substrate was evaluated using a stylus profilometer (DEKTAK 3; Bruker Japan Co.). A stainless-steel mask with an electrode pattern was then placed on the AZrx(Nb1−yTay)2−xBi2+zO9−δ (A = Ca or Sr) library film, and platinum electrodes were sputtered through holes in the mask up to a thickness of 1 μm and annealed at 600° C for 0.5 hours in air. The electrode pattern was an interdigital shape, as shown in Fig. 2(a). At this time, the stainless-steel mask was fixed with a neodymium magnet so that the electrodes did not shift relative to the film location. Platinum electrodes with the patterns shown in Fig. 2(b) and (c) were also sputtered on standard 8YSZ samples of the sheet-sintered body and the sputtered film, respectively, and then annealed at 950° C for 0.5 hours in air. Furthermore, because it is difficult to calculate the precise conductivity of the thin film using the interdigital


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electrodes in Fig. 2(a), two 8YSZ thin films were prepared with the same thickness. Interdigital electrodes were sputtered onto one film, and rectangular electrodes were sputtered onto the other. The conductivity of the 8YSZ thin film with the rectangular electrodes was determined simply from the film thickness and the distance between the two rectangular electrodes. The conductivity of the film with the interdigital electrodes was then calibrated with reference to that of the film with the rectangular electrodes. The HT measurement system is shown in Fig. 3(a) and (b). It comprises a control device, a measurement chamber, an LCR meter (3522–50; HIOKI Co., Ltd., Japan), a control computer, and a monitor. The measurement chamber comprises a cartridge heater and a tungsten probe that operates in the Z direction. The position of the internal sample stage is controlled by an XY stage, and it is possible to measure the impedance continuously and automatically at an arbitrary sample position by the two-probe method at a chosen temperature lower than 1,000° C. In this study, the library was set on the sample stage in the chamber, nitrogen gas flowed until the oxygen concentration reached roughly 20 ppm, and then the library was held at the chosen measurement temperature in the range 500–800° C. Then, scanning the tungsten probe on the substrate, the impedance of each library film at the chosen temperature was measured automatically in the frequency range 1–100 kHz with applied 100 mV voltage. The conductivity of each library film with the interdigital electrodes was evaluated in the same way as described above for the 8YSZ thin films.


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RESULTS AND DISCUSSION An 8YSZ sample was used to confirm the measurement accuracy of the developed HT conductivity-measurement system, which includes two means; (1) positional deviation in the measurement system, and (2) the validity of the accuracy of the conductivity value. First, in order to confirm the positional deviation, we measured the ionic conductivity mapping of 8YSZ sputtered film 700° C as shown in Figure 4(a). In general, the transport number of YSZ exceeds 99%.4 The ionic conductivity was measured between the two rectangular electrodes. The typical Cole–Cole plot of the 8YSZ sputtered film is shown in Fig. 4(b), comprising an impedance curve including the interface impedance of the sample and the Warburg impedance of the electrode. The complex impedance curves were analyzed based on the equivalent circuit model of Fig. 4(c). This model comprises the equipment impedance, the grain impedance, the grain boundary impedance, and the electrode impedance. The simulated curves are plotted in Fig. 4(b) as solid lines. The simulated complex impedance curves fit well with the measured ones, confirming that the proposed equivalent circuit model can explain the experimental data. A prat of 8YSZ sputtered films contained the microcracks due to the large thickness and large area and during the measurements, this part of sample peeled away from the substrate because of the differing thermal expansion between the substrate and the film as shown in Fig. 4(d), causing excessively low conductivity in that part as shown in Fig. 4(a). In order to check the positional deviation, we rotated the sample by 180 ° and measured the conductivities again. As a result, the conductivities in the library reproduced with those at the same sample position in the library. Thus the positional uniformity of the present measurement system was confirmed. Except for that part, the deviation in the distribution of ionic conductivity over the entire film was small, demonstrating


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the reproducibility of the HT conductivity-measurement system, including the homogeneity of the temperature distribution. Second, to assess the validity of the measured conductivity by HT measurement system, the temperature dependences of the ionic conductivity of 8YSZ specimens with different morphologies are compared in Fig. 5. Although the ionic conductivity of 8YSZ differs with specimen type, the conductivity of the same type of specimen as evaluated by the HT measurement system is almost the same as that evaluated by the usual measurement method, thereby ensuring the accuracy of the conductivity as evaluated by the HT measurement system. The ionic conductivity of the bulk-sintered body evaluated with the LCR meter after attaching platinum electrodes and wires to the specimen agrees well with the literature value.4 However, the ionic conductivity of the sheet-sintered body made of the same 8YSZ powder is slightly lower than that of the bulk-sintered body, which we consider to be because of the different densities and microstructures of the different specimen types. The sheet-sintered body contained more pores than sintered compact of 8YSZ. For the 8YSZ sputtered thin film, it took roughly five minutes to measure the conductivity at one point with the HT measurement system and 270 minutes to measure at all 49 points with the electrode pattern in Fig. 2(c). Therefore, for this 49-point library, it took roughly 14 hours to complete the minimum three measurements required for the Arrhenius plot to evaluate the activation energy. Meanwhile, with the conventional method, it takes roughly two hours to evaluate an activation energy of each sample and thus roughly 100 hours to evaluate 49 samples. Next, we used the HT measurements to optimize the composition of the library of the bismuthlayered compound AZrx(Nb1−yTay)2−xBi2+zO9−δ. Generally, to determine the transport number accurately, the electrochemical potential of the concentration cell composed of the target ion


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conductor must be measured.33 Therefore, we prepared bulk-sintered bodies of SrBi2Ta2O9, SrBi2Nb2O9, CaBi2Nb2O9, and Ca2Bi2Ta2O9 as typical compositions of the library film and evaluated the transport number of oxide-ion conduction from the electrochemical potential of their battery cells. Consequently, the oxide-ion transport numbers of these compounds were confirmed to be almost 100%, which are higher than those of previous studies, probably because of the bulk sample conditions, such as the amount of impurities and the compositional deviation from the stoichiometric composition.34 As shown in Fig. 6(a), we then prepared library films of differing composition in six rows by six columns on an alumina substrate and evaluated the conductivity of the AZrx(Nb1−yTay)2−xBi2+zO9−δ library systematically. Although we did not determine the transport number for all compounds in the library, we assumed that they had a similarly high transport number to that of the above stoichiometric compounds. Note that the conductivity was measured under a nitrogen-flow atmosphere to prevent oxidation of the tungsten probe at high temperature. In that case, the conductivity could be dominated by oxide ions because the oxygen concentration is roughly 20 ppm, which corresponds to the plateau in oxide pressure between the hole conductivity and the electron conductivity.34 Before measuring the conductivity, we performed HT XRD measurements on the prepared library films. In this experiment, it took roughly two seconds to measure one library film composition, making it possible to complete the XRD measurements of all the library film compositions in a few minutes. Figure 6(b) shows the typical XRD patterns of the library films. The numbers 1–9 in Fig. 6(b) and (c) correspond to the location numbers of the library film in Fig. 6(a) when XRD measurements were performed. Diffraction peaks attributed to the bismuth-


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layered compounds were observed in all the compositions on the library, whereas no diffraction peaks of the secondary phases were observed other than those of the alumina substrate. The conductivities of the library films at 700° C and 800° C were measured with the HT measurement system and are summarized in Fig. 7(a) and (b), respectively. Assuming a film thickness of 1 μm, the lower limit of the measurable conductivity of the present HT measurement system is around 1 × 10−5 S/cm. At temperatures below 600° C, the conductivity could not be determined because it was below this lower limit for all compositions in the library. Even at 700° C, as shown by the black portion in Fig. 7(a), the conductivity for some of the library film compositions could not be evaluated because it was too low. When the temperature was raised to 800° C, the conductivity for all library film composition reached the measurable range. However, the library films decomposed at 800° C during the conductivity measurement, and a part of the film component, probably bismuth, gradually volatilized. Starting from the rightmost column of library films, the conductivity measurements may have been affected by this decomposition, particularly for the left-most column. Overall, the conductivity was low in the composition range near the center of the library film in which Nb was partially substituted by Ta or Zr, and it was confirmed that the conductivity of the lower-left and upper-right regions tended to be higher. It has been reported that the conductivity of SBN and SBT at 700°C is 1–4 × 10−5 S/cm,31 and the conductivities measured in the present study are close to that range. It has also been reported that the conductivity of SBN and SBT increases with an acceptor doping of 1–10% and decreases with donor doping.31,32 In the present study, Zr was selected as an acceptor dopant because it has an ionic radius that is relatively close to that of Nb. Although the a-axis for the SBN system increased continuously


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with Zr content y, the b-axis and c-axis did not increase linearly with Zr content y larger than 0.1, as shown in Fig. 6(c), which seems to be the solubility limit of Zr. By using the present HT screening system, we have shown that 10% Zr-doped SrNb1.9Zr0.1Bi2O9−δ is the best composition exhibiting the highest conductivity among the AZrx(Nb1−yTay)2−xBi2+zO9−δ library films (10−3 S/cm at 800° C). In addition, at 800° C, relatively high conductivities were also achieved for Ca(Nb0.5Ta0.5)1.7Zr0.3Bi2O9−δ. The conductivity was higher for SBN than for SBT, which agrees with previous results.31,32 Moreover, we have shown that the conductivity increases with decreasing Ta content y. Although the conductivity of compounds containing Ca2+ is yet to be reported, in the present experiment, the conductivity of the nondoped system was higher when the A site was Sr2+ than when it was Ca2+. Moreover, the conductivity decreased upon adding excess Bi3+ for SBN, although the conductivity increased in the region corresponding to high Ta content. It has been reported that Ca2+ replaces Bi3+ sites so as to increase the conductivity as an acceptor dopant.32 However, excess Bi3+ may occupy the Ca2+ site and reduce the conductivity as a donor dopant. For example, 5% donor doping could reduce the conductivity by one order of magnitude.35 Excess Bi content x = 0.1 for SBN corresponds to 5% donor doping, assuming that the excess Bi replaces the Ca2+ completely, which reduces the conductivity of SBN by roughly a half. Although excess Bi is added based on the volatilization of Bi during heat treatment, the difference in Bi volatility according to the composition may affect the conductivity.

CONCLUSIONS To realize rapid searching for OICs, we have developed a novel research method that combines combinatorial synthesis of library films and HT measurements. By applying this


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approach, the optimum composition of the ABi2+z(Nb1−yTay)2−xZrxO9−δ system was investigated efficiently. First, using 8YSZ standard samples, the performance of the HT conductivitymeasurement system was evaluated. The ionic conductivity of 8YSZ obtained by the usual measurement method agreed with that obtained by using the HT conductivity-measurement system, while the total time for the evaluation was reduced by a factor of seven by using the HT system. These results demonstrate the validity of the evaluation values obtained by the HT conductivity-measurement system. The ionic conductivity of the AZrx(Nb1−yTay)2−xBi2+zO9−δ (A = Ca or Sr) system was found to be higher with A = Sr than with A = Ca and to increase with decreasing Ta content. It was also found that a relatively high conductivity of 10−3 S/cm at 800°C was achieved by adding 10% Zr. The overall processing time for material synthesis, phase identification, and conductivity measurement was found to be significantly shortened by using this method.

ACKNOWLEDGMENTS The synchrotron radiation experiments were performed at the BL33XU of SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (JASRI) (proposal nos. 2018A7030, 2017B7030, 2017A7030, 2016A7030, and 2016B7030). The authors thank Dr. Nonaka, Mr. Kisida, and Mr. Takagi at TCRDL for helping with the guidance and setting of the experiment. The authors also thank Ms.Ohba at TCRDL for useful advice for the article preparation.

ASSOCIATED CONTENT Supporting Information.


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Some supporting figures are provided for readers' interest. Microstructure of different types of YSZ samples in Figure 5, complete data of XRD profiles partly provided in Figure 6, and the typical cole-cole plots for YSZ sputtered films in Fig.4(a) and library films in Fig.7 corresponding to high ionic conduction part and low ionic conduction part in each figure. This material is available free of charge via the Internet at http://pubs.acs.org.

AUTHOR INFORMATION Corresponding Author *Phone:+81-561-71-7038. FAX: +81-561-63-6279. E-mail:[email protected] Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Notes ABBREVIATIONS HT: high-throughput; SBN: SrBi2Nb2O9; SBT: SrBi2Ta2O9; SOFC: solid oxide fuel cell; YSZ: yttria-stabilized zirconia

REFERENCES (1) Shao, Z. P.; Haile, S. M.; A high-performance cathode for the next generation of solid-oxide fuel cells. Nature 2004, 431, 170–173.


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(12) Okazaki, S.; Okazaki, N.; Hirose, Y.; Nishimura, J.; Ueno, K.; Ohtomo, A.; Kawasaki, M.; Koinuma, H.; Hasegawa, T. Quantitative Conductivity Mapping of SrTiO3-LaAlO3-LaTiO3 Ternary Composition-Spread Thin Film by Scanning Microwave Microscope Appl. Phys. Express, 2008, 1, 055003-1–3. (13) Kan, D.; Suchoski, R.; Fujino, S.; Takeuchi, I. Combinatorial Investigation of Structural and Ferroelectric Properties of A- and B-site Co-Doped BiFeO3 Thin Films, Integrated Ferroelectrics 2009, 111, 116–124. (14) Chang, H.; Takeuchi, I.; Xiang, X.-D.; A low-loss composition region identified from a thin-film composition spread of (Ba1−x−ySrxCay)TiO3, Appl. Phys. Lett. 1999, 74, 1165–1167. (15) Xiang, C.; Suram, S. K.; Haber, J. A.; Guevarra, D. W.; Soedarmadji, E.; Jin, J.; Gregoire, J. M. High-Throughput Bubble Screening Method for Combinatorial Discovery of Electrocatalysts for Water Splitting ACS Comb. Sci., 2014, 16, pp 47–52. (16) Hasegawa, T.; Fukumura, T. Combinatorial Thin Film Synthesis and its High Throughput Screening for Inorganic Functional Materials J. Vac. Soc. Jpn., 2011, 54, 549–558. (17) Isaacs, E. D.; Marcus, M.; Aeppli, G.; Xiang, X.-D.; Sun, X.-D.; Schultz, P.; Kao, H.-K.; Cargill III, G. S.; Haushalter, R. Synchrotron x-ray microbeam diagnostics of combinatorial synthesis Appl. Phys. Lett. 1998, 73 (13), 1820–1822. (18) M. Ohtani, T. Fukumura, M. Kawasaki,K. Omote, T. Kikuchi, J. Harada, A. Ohtomo, M. Lippmaa, T. Ohnishi, D. Komiyama, R. Takahashi, Y. Matsumoto,and H. Koinuma, "Concurrent x-ray diffractometer for high throughput structural diagnosis of epitaxial thin films,” Appl. Phys. Lett. 2001, 79 (22), 3594–3596. (19) Ohtani, M.; Hitosugi, T.; Y.Hirose, Nishimura, J.; Ohtomo, A.; Kawasaki, M.; Inoue, R.; Tonouchi, M.; Shimada, T.; Hasegawa, T. Development of high-throughput combinatorial terahertz time-domain spectrometer and its application to ternary composition-spread film Appl. Surf. Sci. 2006, 252, 2622–2627.


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(20) Briceno, G.; Chang, H.; Sun, X.; Schultz, P. G.; Xiang, X.-D. A Class of Cobalt Oxide Magnetoresistance Materials Discovered with Combinatorial Synthesis Science 1995, 270, 273– 275. (21) Takahashi, T. Iwahara, H. and Nagai, Y. High oxide ion conduction in sintered Bi2O3 containing SrO, CaO or La2O3 J. Appl. Electrothem. 1972, 2, 97–104. (22) Singh, B.; Ghosh, S.; Aich, S.; Roy, B. Low temperature solid oxide electrolytes (LT-SOE): A review Journal of Power Sources 2017, 339, 103–135. (23) Hiruma, Y.; Nagata, H.; Takenaka, T.; Thermal depoling process and piezoelectric properties of bismuth sodium titanate ceramics J. Appl. Phys. 2009, 105, 084112-1–8. (24) Li, M.; Pietrowski, M.J.; Souza, R.A. De; Zhang, H.; Reaney, I. M.; Cook, S. N.; Kilner, J. A.; and Sinclair, D. C. A family of oxide ion conductors based on the ferroelectric perovskite Na0.5Bi0.5TiO3 Nature Mater. 2012, 13, 31–35. (25) Ma, H. Q.; Lin, K.; Fan, L.L.; Rong, Y.C.; Chen, J.; Deng, J.-X.; Liu, L.-J.; Kawaguchi, S.; Kato, K.; Xing, X.R. Structure and oxide ion conductivity in tetragonal tungsten bronze BaBiNb5O15 RSC.Adv. 2015, 5, 71890–71895. (26) Kajita, S.; Ohba, N.; Suzumura, A.; Tajima, S.; Asahi, R. submitted (27) Newnham, R.E.; Wolfe, R.W.; Dorrian, J.F. Structural Basis of Ferroelectricity in the Bismuth Titanate Family Mater. Res. Bull. 1971, 6, 1029–1039. (28) B.Jimenez, P.Duran-Martin, A.Castro, P.Millan, “Obtention and Characterization of Modified Bi2SrNb2O9 Aurivillius-typeceramics, Ferroelectrics, 1996, 186, 93–96. (29) Noguchi, Y.; Shimizu, H.; Miyayama, M.; Oikawa, K.; Kamiyama, T. Ferroelectric Properties and Structure Distribution in A-site-Modified SrBi2Ta2O9,” Jpn. J. Appl. Phys. 2001, 40, 5812–5815. (30) Voisard, C.; Martin, P. D.; Damjanovic, D.; Setter, N.; Electrical Conductivity of Piezoelectric Strontium Bismuth Titanate Under Controlled Oxygen Partical Pressurew Mat. Res. Soc. Symp. Proc. 2000, 604, 317–322.


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(31) Palanduz, A.C.; Smyth, D.M.; The Similar Defect Chemistry of Highly-Doped SrBi2Ta2O9 and SrBi2Nb2O9 J. Electroceramics, 2005, 14, 123–132. (32) Kumar, M. M.; Ye, Z.-G. Dielectric and electric properties of donor- and acceptor-doped ferroelectric SrBi2Ta2O9 J. Appl. Phys. 2001, 90, 934–941. (33) Wang, S.; Wu, L.; Gao, J.; He, Q.; Liu, M. Oxygen ion transference number of doped lanthanum gallate J. Power Sources 2008, 185, 917–921 (34) PALANDUZ, A.C.; SMYTH, D.M. Defect Chemistry of SrBi2Ta2O9 and Ferroelectric Fatigue Endurance J. Electroceramics, 2000, 5 21–30 (35) Coondoo, I.; Jha, A.K.; Agarwal, S.K. Enhancement of dielectric characteristics in donor doped Aurivillius SrBi2Ta2O9 ferroelectric ceramics J. Eur. Ceram. Soc. 2007, 27, 253–260.


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FIGURE CAPTIONS Figure 1. Settings of high-throughput (HT) x-ray diffraction (XRD) measurement experiment Figure 2. Sample electrode settings. (a) Interdigital electrode pattern sputtered on thin films of a library comprising six rows by six columns. (b) Electrode pattern sputtered on 8YSZ sheetsintered body. The conductivity was measured between the large top two electrodes of this picture. Pt wire was used for the normal measurements. (c) Seven rows by seven columns Pt electrode pattern sputtered on 8YSZ thin film. Figure 3. Design of HT conductivity-measurement system. (a) Appearance of HT measurement system. (b) Photograph of chamber interior. The sample stage operates along the X and Y directions, and the cartridge heater is held under the stage. Figure 4. Conductivity evaluation of 8YSZ sputtered film using HT measurement system: (a) mapping of oxide-ion conductivity at 700 °C; (b) typical Nyquist plot of 8YSZ sputtered film; (c) equivalent circuit of 8YSZ sputtered film when measured with HT evaluator. Rg and Cg are the resistance and capacitance, respectively, of the 8YSZ grains, Rgb and Cgb are the resistance and capacitance, respectively, of the grain boundaries, and R1, R2, and L are the resistances and inductance, respectively, derived from the HT device; (d) photograph of 8YSZ sputtered film after measurement. Figure 5. Temperature dependence of oxide-ion conductivity for various types of 8YSZ sample. Figure 6. HT measurement of XRD profiles of AZrx(Nb1-yTay)2-xBi2+zO9-δ library films: (a) relationship between composition of library film and measurement location; (b) XRD profiles at


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locations 1–6 of the library film; (c) effect of Zr content x on the rate of change of each lattice constant for the SrZrxNb2−xBi2O9−δ system. Figure 7. Ionic conductivity mapping of AZrx(Nb1−yTay)2−xBi2+zO9−δ library films measured at (a) 700 °C and (b) 800 °C.


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For Table of Contents Use Only

×103

HT Syntheses & Evaluations

-Im Z (Ω)

Virtual Screening using Machine Learning Model

2.0 1.0

0 4 0 0.4 0.8 1.2 1.6×10 Re Z (Ω) 3 ×10 1.5 1.0 0.5 0 0 2 4 6 8 ×103

Candidates

-Im Z (Ω)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41


Bi-layered oxide

Re Z (Ω)

Development of a High-Throughput Screening Method for Oxide-Ion Conductors and Its Application to Bismuth-Based Oxide Library Thin Films Masato Matsubara et al. ACS Paragon Plus Environment

ACS Combinatorial Science 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56

XRF detector

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2D-XRD detector

X-ray

Library A web camera checks the corner positions of the sample automatically.

Figure1 Matsubara et al. ACS Paragon Plus Environment

Page 25 of 30


0.3mm 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56

(a)

Pt electrode 0.3mm

30mm 3mm

(b) Pt wire 0.99mm 10.1mm

(c)

0.7mm 2mm Pt electrode


ACS Combinatorial Science 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56

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(b)

(a)

tungsten probe Controller device

sample stage Cartridge heater sample chamber


(a)

700°C -1 -2 -3 -4

logσ (S/cm)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56


-5

(c)

R1

R2

Rｇ

×105 17.5 12.5 (b) 7.5 2.5 -2.5 Rg Rgb -7.5 Impedance of -12.5 equipment -17.5 20 0 10 Re Z (Ω)

-Im Z (Ω)

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(d) Rｇb Zw

L Impedance of equipment

Cg

Cgb


30 5 ×10


spattered film (HT measurement) sheet sintered body(HT measurement) sheet sintered body(usual measurement)

-0.5 Ionic conductivity logσ (S/cm)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56

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bulk sintered body(usual measurement) + reference (4)

-1-1

-1.5 -2-2

-2.5 -3-3

-3.5 -4-4 -4.5

0.7 0.7

0.9 0.9

1.1 1.1

1.3 1.3

1000/T (K-1)


1.5

1.5

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z=0.06 z=0.1

Z=0

Ta content y

0.50 (1)

A=Ca

1.00 (2) 0.75 (3) 0.50 (4)

A=Sr

0.25 (5) 0

(6) (7) (8) (9) 0 0.1 0.2 0.3 0.2 0.2 Zr content x (a)

Changing rate of lattice constant (%)

315

315

1113

220 2010 220 2010

1113

0010

200

0010

(2)

200

008

(1)

115

Al2O3 substrate

115

Intensity (a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 4525 25 46 47 48 49 50 51 52 53 54 55 56


(3) (4) (5) (6) 30

35 35

40

45 45

50

55 55

60

1 0.9 0.8 0.7 0.6 0.5

c-axis

0.4 0.3

b-axis

0.2

a-axis

0.1 0

65 65

0

0.1

0.2

Zr content x

2θ (deg./CuKα) (b)

(c) Figure6 Matsubara et al. ACS Paragon Plus Environment

0.3


z=0

z=0.06 z=0.1 A=Ca

0.50

0.75 A=Sr

0.50

-3.0

0.25

-3.5 0

-4.0 0

0.1

0.2 0.3 0.2 Zr content x

0.2

-4.5

-5.0

Development of a High-Throughput Screening Method for Oxide-Ion

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