Thermal Analysis and Phase Relations in the Pseudobinary System

Article pubs.acs.org/crystal

Thermal Analysis and Phase Relations in the Pseudobinary System La2W2O9−Li2W2O7 Jair Ricardo de Moraes,† Detlef Klimm,‡ Vera Lucia Mazzocchi,† Carlos Benedicto Ramos Parente,† Steffen Ganschow,‡ and Sonia Licia Baldochi*,† †

Instituto de Pesquisas Energéticas e Nucleares, IPEN−CNEN/SP, Av. Prof. Lineu Prestes, 2242, Cidade Universitária 05508-000, São Paulo, SP, Brazil ‡ Leibniz Institute for Crystal Growth, IKZ−Berlin, Max-Born-Straße 2, 12489 Berlin, Germany ABSTRACT: The pseudobinary phase diagram La2W2O9−Li2W2O7, which is an isopleth section of the Li2O−WO3−La2O3 ternary, is described for the first time. It contains the 1:1 intermediate phase LiLa(WO4)2(ss) = x Li2W2O7−(1 − x)La2W2O9 with a homogeneity region 0.48 ≤ x ≤ 0.546. LiLa(WO4)2(ss) is a prospective laser host material, and single-crystal fibers could be grown by a micro-pullingdown technique. LiLa(WO4)2 undergoes peritectic melting at 998 ± 5 °C for x = 0.48. A eutectic point exists between LiLa(WO4)2 and Li2W2O7 at 722 ± 5 °C and 90 mol % Li2W2O7.

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INTRODUCTION Tetragonal scheelite-like double tungstates belong to the family of ARE(WO4)2 compounds consisting of alkali (A = Li, Na, K, Rb) and rare earth (RE = Y, Sc, La−Lu) cations. The structures are disordered such that the alkali and rare earth cations are statistically distributed at the same lattice site. Such cationic distribution strongly influences the optical properties of the materials in such a way that it generates a locally variable crystalline field that leads to the broadening of the absorption and luminescence lines of dopant ions.1 This property is highly desired for solid-state lasers because wider absorption improves the efficiency of the pumping process during laser operation and results in broader luminescence lines, making the development of tunable emitters possible. Structural and optical properties2,3 as well as laser action4 were reported recently. In this context, the double tungstates ARE(WO4)2 were often described as intermediate phases in the A2WO4− RE2(WO4)3 binary systems,5,6 which corresponds to the dashed-solid line in Figure 1. All of these systems contain the above cited double tungstates with composition ARE(WO4)2 nearly or at stoichiometric composition. The description in these pseudobinary systems seemed appropriate because of crystallographic similarities. Unfortunately, Li2WO4 is a borderline peritectic,7,8 and only some of the RE2(WO4)3, such as Dy2(WO4)3, melt congruently. For the larger RE3+ ions, such as Nd3+ or La3+, peritectic decomposition of the RE2(WO4)3 is observed instead.9 Binary phase diagrams, however, can be spanned only between end members with congruent melting. Presentations such as LiNd(WO4)2−Nd2(WO4)310 cannot be binary phase diagrams, and this argument holds for all systems with incongruently melting RE2(WO4)3 as end members. Evdokimov et al.5 reported the phase diagram LiLa(WO4)2− La2(WO4)3 as a binary system. Contradictory results on the © 2014 American Chemical Society

Figure 1. Concentration triangle 0.5Li2O−0.5La2O3−WO3. The basis of the binary rim systems 0.5Li2O−WO37,8 and 0.5La2O3−WO311 correspond to 650 °C. LiLa(WO4)2 is at the intersection of the La2W3O12−Li2WO4 and La2W2O9−Li2W2O7 junctions.

melting behavior of La2(WO4)3 are reported in the literature. Ivanova11 described incongruent melting, but congruent melting was found by Yoshimura.12 In preliminary analysis, we verified that Ivanova11 is correct. In a recent study about the growth of single-crystalline LiLa(WO4)2 fibers,13 it was shown that the fibers can be grown only if the melt contains an excess of Li2W2O7. This strongly suggests that LiLa(WO4)2 melts incongruently. Consequently, the phase diagram LiLa(WO4)2− La2(WO4)3 cannot be regarded as binary. Regarding the ternary system Li2O−La2O3−WO3, we reviewed a short range of the rim systems Li2O−WO3 and La 2 O 3 −WO 3 , respectively, in order to confirm which Received: June 13, 2014 Revised: September 15, 2014 Published: October 3, 2014 5593

dx.doi.org/10.1021/cg500824r | Cryst. Growth Des. 2014, 14, 5593−5598

Crystal Growth & Design

Article

For scanning electron microscopy (SEM), samples were produced by melting appropriate powder mixtures in small (0.3 mL) Pt crucibles. The solidified samples were cut, polished, and covered with carbon to bleed off surface charge and analyzed with a HITACHI tabletop TM3000 microscope equipped with a Bruker EDS Quantax 70. The SEM analysis was performed with an acceleration voltage of 5 kV, and the EDS measurements were carried out for 80 s at each point at 15 kV. Fiber Crystal Growth. On the basis of the phase diagram that was constructed in this study, single-crystal fibers of LiLa(WO4)2 were grown by the micro-pulling-down (μ-PD) technique in an inductively heated apparatus. Accounting for the peritetic decomposition of LiLa(WO4)2, fibers were grown from the melt enriched by an excess of 5, 3, and 1.5 mol % Li2W2O7 with respect to the stoichiometric composition. A Pt95Ir5 crucible and a NaLa(WO4)2 seed prepared from a Czochralski grown crystal were used. The pulling rate was 0.04 mm min−1, and the growth was performed in air. The growth apparatus is described in more detail elsewhere.16

compounds melt congruently. It was verified that Li2WO4, Li2W2O7, Li2W4O13, and La2(WO4)3 melt incongruently and that the only congruently melting compound is La2W2O9. Fortunately, its melting temperature, Tf = 1600 °C, is rather high, which leads to a high position of the ternary liquidus surface in the vicinity of this compound (Figure 1). This means that the region where La2W2O9 crystallizes first is expected to extend wide from the rim into the ternary region of the concentration triangle. For that reason, La2W2O9 was chosen as the congruent starting point for the construction of an pseudobinary section through the concentration triangle with the incongruently melting Li2W2O7 as the end member. Both end members have narrow stoichiometry fields in their respective binary system, and the pseudobinary section that is indicated by a horizontal dashed line in Figure 1 crosses LiLa(WO4)2 midway. In this work, we propose the experimental phase diagram for the La2W2O9−Li2W2O7 pseudobinary section. The construction was based on differential thermal analysis (DTA), and the phases were determined by X-ray powder diffraction (XRD) with subsequent Rietveld analysis. In addition, the influence of doping (the partial substitution of La by other RE) was investigated, and fiber crystal growth experiments were performed.

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RESULTS AND DISCUSSION Thermal Analysis of the System Li2W2O7−La2W2O9. Over the whole range of compositions, the DTA heating curves show four distinct endothermic peaks and one exothermic peak. Starting from x = 0, according to xLi2W2O7−(1 − x)La2W2O9, all peaks were named and characterized in their sequence of appearance in Figure 2.

EXPERIMENTAL SECTION

Differential Thermal Analysis (DTA). Li2CO3, La2O3, and WO3 powders with ≥99.99% purity from different suppliers were used as starting materials, and in previous DTA runs, their reactivity with different crucible materials was checked. It was found that Pt95Ir5 crucibles with lids are stable and well suited. A mixture of raw reagents in the appropriate ratio was prepared for each of the compounds La2W2O9 and Li2W2O7. Since La2O3 is slightly hygroscopic, the percentage of dehydration was considered in the composition, and the amount of powder mixture for La2W2O9 was kept constant in the crucible to minimize stoichiometry deviation. The mixture for Li2W2O7 was subsequently added for each new experiment. In order to achieve better sample homogenization, two subsequent heating and cooling steps were performed, and only the second running was considered for analyzing. The data were collected in a NETZSCH STA449 Jupiter thermal analysis instrument. All measurements were performed under a 20 mL/min oxygen flow and with constant thermal rates of ±10 K/min. Temperature and sensibility calibrations were performed at the melting points of In, Zn, and Au and at the phase transformation of BaCO3, respectively, and a systematic temperature error not exceeding ΔTsys = ± 2 K was found. Because the sample compositions were determined on a balance with 0.01 mg resolution (total sample mass in the order of 35 mg), concentration errors can be neglected compared with ΔTsys. If appropriate, then the statistical error of thermal events was measured from the standard deviation of onset temperatures from several measurements, and this ΔTstat was found to be slightly higher than ΔTsys. X-ray Powder Diffraction and Scanning Electron Microscopy. For XRD analysis, samples with larger masses were mixed and ground separately, heated in Pt crucibles to the melting temperatures, and cooled with a constant rate of 50 K/h in a tubular furnace equipped with a Novus N1200 temperature controller. XRD data were collected at room temperature in a powder diffractometer (Panalytical, model Xpert Pro MPD) operated at 40 kV and 40 mA with a Co cathode (λKα = 1.7902 nm) that was equipped with a hybrid monochromator (mirror and Ge monochromator) for the incident beam and with Pixel detection technology. The 2θ range varied from 10° to 120°. Rietveld analysis was performed with GSAS software,14 considering the crystallographic data sets from ICSD (Inorganic Crystal Structure Database)15 of La2W2O9 no. 93721, LiLa(WO4)2 no. 261829, Li2W2O7 no. 21048, Li2WO4 no. 10479, Li2CO3 no. 66941, Li2O no. 173206, and La2O3 no. 160205.

Figure 2. DTA heating curves in the range 0.02 ≤ x ≤ 0.90 (x, mole fraction of Li2W2O7).

In the region 0 ≤ x ≤ 0.5, peak I is quite broad and initially small, with an onset temperature varying from 1052 °C (only for x < 0.1) to 1000 °C. It can be attributed to the peritetic decomposition of LiLa(WO4)2, which is broad and variable in T because this substance is a solid solution (ss). The temperature variation for small x is in agreement with the results of ref 5 on the La2W3O12−Li2WO4 section in Figure 1, where the decomposition of LiLa(WO4)2 starts higher for the La-rich composition (1056 °C) compared to that for the Li-rich compositions (1032 °C). For 0.50 ≤ x ≤ 0.58, peak I becomes even broader, and the onset temperature decreases to 921 °C. For x > 0.584, peak I cannot be seen in the heating curves. However, a corresponding exothermic peak in the cooling curves, in the range 0.50 ≤ x ≤ 0.90, can be attributed to the crystallization of LiLa(WO4)2 at its liquidus temperature (Figure 3). Peak II, with an onset temperature of 1084 °C, is sharper. Similar to peak I, it appears for La-rich compositions; it 5594



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Figure 3. DTA cooling curves in the range 0.50 ≤ x ≤ 0.90.

becomes smaller with increasing Li content and disappears for x ≥ 0.48. This peak is attributed to the α-to-β phase transition of La2W2O9, in agreement with the La2O3−WO3 phase diagram.11,12 For x > 0.368, two different endothermic peaks with onset temperatures of 668 °C (peak III) and 722 °C (peak IV) (Figure 2) are observed. Such peaks remain until x = 1.0. Peak III becomes continuously larger if the composition approaches the Li2O−WO3 rim system (Figure 1). Its onset is close to, but somewhat lower than, the eutectic transition Li2WO4−Li2W2O7 that was found at (692 ± 3) °C.7 One can assume that peak III results from a ternary invariant, possibly a transient peritectic near the Li2O−WO3 rim, and is close to the Li2WO4−Li2W2O7 eutectic. Peak IV is related to the eutectic between LiLa(WO4)2 and Li2W2O7. The eutectic composition can be found at x = 0.90, where the crystallization peak of LiLa(WO4)2 completely disappeared (Figure 3). The area of peak II, AII(x), is a linear function of the concentration. The fitted AII(x) is expected to disappear at the homogeneity field of LiLa(WO4)2. In fact, AII(x) = 0 is found for x = 0.480 ± 0.005 (Figure 4a). The same area analysis was applied for peak IV (AIV(x)), which also depends linearly on concentration and disappears at the homogeneity field of LiLa(WO4)2 (Figure 4b). This was found for x = 0.546 ± 0.016, and both values represent the homogeneity limits of LiLa(WO4)2, which is shown in the phase diagram in Figure 5. In preliminary LiLa(WO4)2 crystal growth experiments, it was observed that the control of the crystallization interface, for crystals doped with different RE ions, proceeds partially easier (with no/short transient phase) and partially more difficult (with long transient phase) than that of the undoped material.13,17 It should be noted that melt crystal growth is straightforward only for congruently melting compounds in which the liquid and solid phases with identical composition are in equilibrium. Also “borderline peritectics”, where the solidus, the liquidus, and the liquidus of the higher melting phase (here, La2W2O9) meet in one point, can be grown.18 The influence of partial La substitution by three rare earth elements (Gd, Nd, and Yb in concentrations of 1 and 2 mol %) on the melting behavior of LiLa(WO4)2 was investigated by DTA. Peak II relates to La2W2O9 and disappears in the homogeneity range of LiLa(WO4)2. Substituting La for Gd keeps La2W2O9 stable up to xGd = 0.490 and Yb up to xYb = 0.473 (Figure 4c). The experimental error was significant only for 1.0 mol % RE-doping (except for Gd), and, for that reason,

Figure 4. (a) AII(x) as a linear function of Li2W2O7 concentration. The homogeneity region of LiLa(WO4)2 corresponds to AII(x) → 0 at x = 0.480 ± 0.005. (Error determined by the average difference between both prediction lines.) (b) AIV(x) as a linear function of Li2W2O7 concentration. The homogeneity region of LiLa(WO4)2 ends at x = 0.546 ± 0.016. (c) La-rich limit of the LiLa1−yREy(WO4)2 homogeneity range as a function of RE-doping. Gd or Yb enforces or reduces the incongruent melting behavior, respectively (see also Figure 5).

the comparisons for the different RE revealed no clear results. However, for 2 mol % doping, the errors became smaller, and it was revealed that for Nd and Gd the incongruency of LiLa(WO4)2 is slightly higher (≳1 mol %) and for Yb it is slightly lower (≲1 mol %) than the x = 0.48 composition, which was found for undoped La2W2O9. Here, incongruency means the difference in x by which the La2W2O9 liquidus and the LiLa(WO4)2 (LLW) solidus are touching the peritectic line in Figure 5. 5595



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and Li2W2O7. Nassau21 reported that the formation of an amorphous metastable phase of composition Li2W2O7 occurs, which one reacts exothermally with other components during the formation of crystalline phases. However, it is still not clear how the treatment at low temperatures and the presence of Li2W2O7 influences the tendency of glass formation of glassy LiLa(WO4)2, and further investigation is out of the scope of this study. XRD Analysis. XRD spectra for different powder samples are shown in Figure 6, and the results of quantitative Rietveld

Figure 5. Equilibrium phase diagram for Li2W2O7−La2W2O9. Dashed lines describe the influence of Gd 1.0 mol % (red) and Yb 2.0 mol % (blue) compared to that for undoped LLW = LiLa(WO4)2.

The onsets of DTA peaks and the composition ranges and attributes where these peaks occur are summarized in Table 1. Table 1. Peak Onset Temperatures and Composition Ranges Observed for the xLi2W2O7−(1 − x)La2W2O9 Systema Tonset (°C) 1000 1084 668 722

composition x 0.10 ≤ x ≤ 0.50 0.00 ≤ x ≤ 0.47 0.368 ≤ x ≤ 1.00 0.368 ≤ x ≤ 0.975

comment peak peak peak peak

I II III IV

a

Origins of the peaks: I, peritectic decomposition of LiLa(WO4)2(ss); II, α/β transition of La2W2O9; III, ternary invariant, possibly a transient peritectic near the Li2O−WO3 rim and close to the Li2WO4− Li2W2O7 eutectic; IV, eutectic Li2W2O7−LiLa(WO4)2(ss).

Figure 6. XRD spectra for annealed samples from x = 0 (La2W2O9) to x = 1 (Li2W2O7).

phase analysis are presented in Table 2. For some samples that were only partially melted, traces of the reagent compounds were found. The following ranges for the different phases were established: 0.00 ≤ x ≤ 0.50 for α-La2W2O9, 0.0 < x < 1.0 for LiLa(WO4)2, and 0.546 < x ≤ 1.0 for Li2W2O7. Table 3 shows the variation of LiLa(WO4)2 lattice parameters and occupation factors across the region of homogeneity discussed above. These results agree with a defective solid solution phase.22 Lattice parameter c0 presents a stronger variation compared to that for a0, whereas the occupation factors for Li and La change. The higher the Li occupation, the smaller are the cell parameters for x = 0.48 and vice versa for x = 0.51. SEM (with EDX) analysis revealed the formation of LiLa(WO4)2 as major phase and α-La2W2O9 as a segregation, in agreement with the phase diagram in Figure 5. Fiber Crystal Growth. In order to compare their characteristics (Table 4), fibers were grown from the melt with different compositions in the range 0.55 ≥ x ≥ 0.46 because the peritetic decomposition of LiLa(WO4)2 happens in this range. From the enriched melt by an excess of Li2W2O7 in the range 0.55 ≥ x ≥ 0.50, after an initial translucent seeding region, transparent LiLa(WO4)2 μ-PD crystal fibers grew that had a constant diameter (Figure 7). Fibers that grew were completely opaque and irregular in diameter for x = 0.46. XRD phase analysis revealed phase purity (except for x = 0.46); all peaks could be indexed with ICSD data. The prediction that the RE dopants influence the melting was also confirmed. 2.0 mol % Nd-doped fibers could be grown only from higher values of x to a limit of x = 0.516. On the other hand, 2.0 mol % Yb-doped fibers could be grown until the limit of x = 0.503. In both cases, no initial transients were

On this basis, the equilibrium phase diagram Li2W2O7− La2W2O9 is proposed in Figure 5. LiLa(WO4)2 is a compound exhibiting some finite homogeneity range that melts peritetically at 1000 °C. Glass Formation. Immediately beyond peak III (corresponding to the eutectic Li2WO4−Li2W2O7), an exothermal effect is observed in the heating curves only in the range 0.420 ≤ x ≤ 0.500. If an isothermal treatment was performed just below peak III at 665 °C for 1 h, then this exothermal effect was suppressed only for the subsequent run. One can assume that this effect is due to the formation of a metastable phase. For some samples in the range 0.50 ≤ x ≤ 0.80, similar heat treatments were also performed. Then, in the cooling curves, shifts of the baseline position immediately before LiLa(WO4)2 crystallization occurred. This change indicates variations in the heat capacity of the melt, which is a characteristic phenomenon of viscosity variation by glass formation. Higher annealing times tend to result in larger baseline shifts. This effect was also observed recently for microcrystals (obtained by the polymerizable complex method) treated for 12 h for organic precursor removal.17 It is known that the systems Li2O−WO3 and La2O3−WO3 present composition regions where glass formation occurs; however, this occurs only for cooling rates higher than those used in this study. For La2O3−WO3, the glass formation region was found to be 0.80 ≤ x ≤ 0.85, and the glass transition temperature is ≈533 °C.19 For the Li2O−WO3 system, the glass formation region is around 0.50 ≤ x ≤ 0.725, with temperatures varying as a function of x between 346 and 490 °C.20 This is almost the primary crystallization range of Li2WO4 5596



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Table 2. Phase Content (%) for Different Annealed Powder Mixtures in the System xLi2W2O7−(1 − x)La2W2O9 Identified by Rietveld Analysisa x

LiLa(WO4)2

0.00 0.10 0.35 0.45 0.46 0.47 0.48 0.49 0.50 0.51 0.52 0.65 0.90 1.00 a

La2W2O9 100.00 70.93 17.51 10.60 6.77 2.25 6.93 1.01 1.32

29.07 82.49 85.35 78.36 97.75 89.66 79.95 77.90 87.20 77.14 46.82 14.28

Li2W2O7

Li2WO4

4.05 11.21

3.67

3.42 19.04 20.78 12.80 9.14

13.71 53.18 85.72 100.00

Rp

Rwp

S

sample aspect

0.3605 0.3869 0.4078 0.3548 0.3395 0.3599 0.3494 0.3672 0.3717 0.3781 0.3663 0.3815 0.3367 0.2754

0.2755 0.2967 0.3094 0.2687 0.2592 0.2747 0.2617 0.2766 0.2813 0.2874 0.2791 0.2869 0.2547 0.3644

1.2 1.3 1.2 1.1 1.1 1.1 1.1 1.2 1.2 1.1 1.1 1.2 1.1 1.2

solid part. melted melted part. melted part. melted part. melted part. melted part. melted part. melted part. melted part. melted part. melted melted part. melted

Rwp and Rp, weighted or unweighted profile, respectively.

Table 3. Cell Parameters of LiLa(WO4)2(ss) and Li, La, and O Occupation Factors x

a0

c0

Li occ.

La occ.

O occ.

0.48 0.49 0.50 0.51 0.52

5.323(1) 5.327(2) 5.328(2) 5.328(2) 5.330(2)

11.528(4) 11.576(7) 11.581(7) 11.582(7) 11.611(8)

0.55(6) 0.54(8) 0.51(7) 0.52(8) 0.54(8)

0.45(6) 0.46(8) 0.49(7) 0.48(8) 0.46(8)

1.0 0.9(5) 1.0 0.9(4) 0.9(4)

Table 4. Melt Starting Compositions Based on xLi2W2O7−(1 − x)La2W2O9 and Characteristics of As-Grown LLW Fiber Crystals x

dopant (mol %)

fiber’s aspect

0.464 0.514 0.530 0.551 0.516 0.503

undoped undoped undoped undoped Nd (2.0) Yb (2.0)

opaque and irregular transparent and uniform transparent and uniform transparent and uniform transparent and uniform transparent and uniform

Figure 8. DTA curves of LiLa(WO4)2 fibers grown by the μ-PD technique.

sharp melting peak, instead showing a smeared melting range, which is confirmed by the broad melting and crystallization peaks. The peak broadening is further increased by the peritectic decomposition where LiLa(WO4)2(ss) is indirectly transformed to melt, with intermediate formation of the higher melting phase La2W2O9.

observed, and the quality and uniformity of the fibers were preserved. This results corroborates this phase diagram study. DTA melting/crystallization curves for fibers grown from different compositions are shown in Figure 8 and are in agreement with the phase diagram in Figure 5. The somewhat different onset temperatures for LiLa(WO4)2(ss) melting results from the slightly different compositions of the solid solution phase. Additionally, solid solutions often show no

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CONCLUSIONS The partial re-evaluation of the ternary system Li2O−La2O3− WO3 was performed in order to experimentally establish the pseudobinary section La2W2O9−Li2W2O7. There the inter-

Figure 7. As-grown LLW fibers from different melt starting compositions: (a) x = 0.550, (b) x = 0.530, (c) 2.0 mol % Nd-doped x = 0.516, and (d) x = 0.464. 5597



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mediate LiLa(WO4)2(ss) melts peritectically at ≲1000 °C, depending on composition. LiLa(WO4)2(ss) = xLi2W2O7−(1 − x)La2W2O9 presents a homogeneity region 0.48 ≤ x ≤ 0.546, and an eutectic point of the system exists at x = 0.90. RE doping influences the LiLa(WO4)2(ss) melting behavior such that Gd enhances incongruency and Yb enhances congruency. Single-crystal fibers (crack free and transparent) can be obtained from melts with a minimum excess of Li2W2O7 of 1.5 mol %.

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(20) Tatsumisago, M.; Sakono, I.; Minami, T.; Tanaka, M. J. Mater. Sci. 1982, 17, 3593−3597. (21) Nassau, K.; Glass, A. M.; Grasso, M.; Olson, D. H. J. Electrochem. Soc. 1980, 127, 2743−2747. (22) Trunov, V. K.; Evdokimov, A. A. Sov. Phys.−Crystallogr. 1975, 19, 616−617.

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Phone: +55 11 3133 9355. Fax: +55 11 3133 9374. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors are indebted to Dr. I. M. Ranieri (CLA, IPEN, São Paulo) for fruitful discussions. We acknowledge the XRD measurements done by Prof. Sasaki at the X-ray Laboratory of Universidade Federal do Ceará, Brazil. This work was financially supported by the Coordenaçaõ de Aperfeiçoamento do Ensino Superior (CAPES, Brazil), Deutscher Akademischer Austausch Dienst (DAAD, Germany) (research project PROBRAL no. 368/11 and grant no. 9658/11-4), and Fundaçaõ de Amparo à Pesquisa do Estado de São Paulo (FAPESP, Brazil) (grant no. 2008/10721-9).

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REFERENCES

(1) Méndez-Blas, A.; Rico, M.; Volkov, V.; Cascales, C.; Zaldo, C.; Coya, C.; Kling, A.; Alves, L. C. J. Phys.: Condens. Matter 2004, 16, 2139−2160. (2) Han, X.; Garíca-Cortés, A.; Serrano, M. D.; Zaldo, C.; Cascales, C. Chem. Mater. 2007, 19, 3002−3010. (3) de Moraes, J. R.; Baldochi, S. L.; Soares, L. D. R. L.; Mazzocchi, V. L.; Parente, C. B. R.; Courrol, L. C. Mater. Res. Bull. 2012, 47, 744− 749. (4) Zharikov, E. V.; Zaldo, C.; Diaz, F. MRS Bull. 2009, 34, 271−276. (5) Evdokimov, A. A.; Trunov, V. K.; Spitsyn, V. I. Dokl. Akad. Nauk SSSR 1972, 207, 1409−1412. (6) Rode, E. Y.; Karpov, V. N.; Ivanova, M. M. Russ. J. Inorg. Chem. 1971, 16, 905−908. (7) Chang, L. L. Y.; Sachdev, S. J. Am. Ceram. Soc. 1975, 58, 267− 270. (8) Hauck, J. J. Inorg. Nucl. Chem. 1974, 36, 2291−2298. (9) Rode, E. Y.; Balagina, G. M.; Ivanova, M. M.; Karpov, V. N. Russ. J. Inorg. Chem. 1968, 13, 1451−1456. (10) Klevtsov, P. V.; Kharchenko, L. Y. Izv. Akad. Nauk SSSR, Neorg. Mater. 1968, 4, 1985−1988. (11) Ivanova, M. M.; Balagina, G. M.; Rode, E. Y. Inorg. Mater. 1970, 6, 801−805. (12) Yoshimura, M.; Rouanet, A. Mater. Res. Bull. 1976, 11, 151−158. (13) de Moraes, J. R. MSc. Dissertation, Universidade de São Paulo, 2009. (14) Larson, A. C.; Dreele, R. B. V. General Structure Analysis System (GSAS); Los Alamos National Laboratory: Los Alamos, NM, 2004. (15) Fachinformationszentrum Karlsruhe, Inorganic Crystal Structure Database. http://www.portaldapesquisa.com.br/databases/sites. (16) Klimm, D.; Ganschow, S. J. Cryst. Growth 2005, 275, e849− e854. (17) de Moraes, J. R. Ph.D. Thesis, Universidade de São Paulo, 2013. (18) dos Santos, I. A.; Klimm, D.; Baldochi, S. L.; Ranieri, I. J. Cryst. Growth 2012, 360, 172−175. (19) Yoshimoto, K.; Masuno, A.; Inoue, H.; Watanabe, Y. J. Am. Ceram. Soc. 2012, 95, 3501−3504. 5598


Thermal Analysis and Phase Relations in the Pseudobinary System

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