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Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX
Emerging Investigators in Solid-State Inorganic Chemistry
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interlayer species in an existing compound to produce a new phase. The Goldberger group demonstrates the isolation of several polytypes of 2D germanane via deintercalation of precursor germanide Zintl phases (https://pubs.acs.org/doi/ 10.1021/acs.chemmater.7b04990).7 The Rodriguez group uses a related process to convert KCo2X2 (X = S or Se) into the antiPbO types CoS and CoSe (https://pubs.acs.org/doi/10.1021/ jacs.6b10229).8 While these low-temperature processes delicately tweeze out specific atoms from a host structure, a bruteforce approach can also be used to hammer out new phases. The Freedman and Laniel groups both make use of laser-heated diamond anvil cells to achieve a combination of high pressure and high temperature, which have enabled the isolation of new Cu/Bi binary intermetallics and unstable metal nitrides such as FeN 2 (https://pubs.acs.org/doi/10.1021/acs.chemmater. 7b01418 and https://pubs.acs.org/doi/10.1021/acs. inorgchem.7b03272).9,10 The advent of advanced computational packages has enabled the “in silico” synthesis and characterization of solids. Calculations can point out hypothetical compounds predicted to be stable under certain conditions. The Morris group uses the ab initio random structure searching method combined with high-throughput screening from the Inorganic Crystal Structure Database to identify likely intermediate phases in the Li/Sb and Li/Sn systems that form during cycling of lithium-ion batteries with tin- or antimony-based anodes (https://pubs.acs.org/doi/ 10.1021/acs.chemmater.6b04914).11 Brgoch and co-workers use quantum-mechanical calculations and machine learning to predict the elastic moduli of compounds in the Pearson Crystal Database, in search of a high-hardness material. This approach enabled them to target two multinary carbides for synthesis; subsequent measurements confirmed that ReWC0.8 and Mo0.9W1.1BC are indeed promising ultraincompressible hard metals (https://pubs.acs.org/doi/10.1021/jacs.8b02717).12 The study of magnetic materials is also being aided by computational methods. The magnetic properties of intermetallic compounds are highly dependent on the band structure, in particular the positioning of partially filled d bands (or f states) with respect to the Fermi level. The utility of spin-polarized band-structure calculations and crystal orbital Hamilton population analysis is demonstrated by the Janka group on the low-temperature ferromagnet EuAu3Al2 and by the Fokwa group on Hf2MnRu5B2, which exhibits competing ferromagnetic and antiferromagnetic states in the chains of manganese atoms in its structure (https://pubs.acs.org/doi/10.1021/acs.inorgchem. 6b01530 and https://pubs.acs.org/doi/10.1021/acs. inorgchem.7b01758).13,14 Computational work is also vital to the study of materials that exhibit exotic electronic phenomena such as Weyl semimetals or topological insulators, compounds of great recent interest that exhibit bulk insulator behavior but have highly conducting surface states. A review by Schoop et al. describes the necessary features of the band structure that cause these phenomena and presents a guide for predicting and
olid-state chemistrythe study of the synthesis, structure, and properties of solidshas historically played a pivotal role in science and technology. Inorganic solids such as silicon, steel, and metal oxide ceramics have driven the electronic age and enabled modern living. These materials are thermodynamically stable and are manufactured by traditional high-temperature synthesis and processing techniques to control the structure and composition. Alternatively, metastable or kinetically stabilized phases can be accessed by lower-temperature “chimie douce” (soft chemistry) reactions, which allow for the rational design and assembly of building blocks; these methods include solvothermal synthesis or topochemical transformations. The advent of X-ray crystallography has been particularly crucial to the field, enabling the understanding of structure, symmetry, and bonding in crystalline inorganic extended solids. Seminal work in solid-state chemistry includes the synthesis of cuprate superconductors that broke the 77 K barrier to make them practical for use, the discovery of the reversible intercalation chemistry of layered sulfides by Whittingham that led directly to today’s rechargeable batteries, the discovery of rare-earth-based magnetic materials such as SmCo5 and Nd2Fe14B, and the development of zeolite catalysts that enabled the growth of the petrochemical industry (for good or ill).1−4 This is not an inclusive list, nor does it cover the work of solidstate physicists, although it must be noted that the field of inorganic solid-state chemistry is highly interdisciplinary, spanning the disciplines of chemistry, physics, and engineering! This diverse mix of science and scientists is reflected by the Articles in this Inorganic Chemistry Virtual Issue “Emerging Investigators in Solid-State Inorganic Chemistry”. This issue highlights the work of up-and-coming young researchers in the field and features collaborations between several departments and universities, as well as the use of advanced facilities at national laboratories. The investigators included have started their independent laboratories in the past 5−8 years and published notable papers in the selected journals Inorganic Chemistry, Chemistry of Materials, and Journal of the American Chemical Society since 2016. Given the broad scope and international reach of research in solid-state chemistry, this collection cannot include all of the rising stars in the field. However, this cross section will hopefully provide a sample of the diverse nature of this growing area of science. Several articles focus on the use of nontraditional synthesis methods to produce metastable phases. Both the Hoch and Zaikina groups are exploring the formation of complex intermetallic compounds. The former group uses low-temperature electrocrystallization, which enables the isolation of new binary compounds such as CsIn12 (https://pubs.acs.org/doi/ 10.1021/acs.inorgchem.6b02068).5 The latter group is making use of metal hydrides as alternatives to alkali-metal reactants in syntheses that target semiconducting Zintl phases such as K 8−x Zn 18+3x Sb 16 (https://pubs.acs.org/doi/10.1021/acs. chemmater.8b04211).6 Another avenue to metastable compounds is via modification of a starting material. For example, topochemical deintercalation processes involve the removal of © XXXX American Chemical Society
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further optimized the thermoelectric properties via Sb doping (https://pubs.acs.org/doi/10.1021/jacs.8b02691).23 Recent improvements of in situ characterization techniques are driving the discovery and optimization of materials. The “panoramic synthesis” diffraction method, wherein a reaction is carried out in a heated sample holder in a diffractometer, allowing for the observation of melting, crystallization, and phase transformation events, has proven to be extremely powerful for the detection of intermediate phases that may form and interconvert during heating or cooling of a reaction mixture.24,25 The use of this technique has recently been demonstrated by Shoemaker and co-workers, who couple in situ diffraction studies of the Ba/Ru/S system with computational work to detect a new high-temperature polymorph of BaS2 and indicate two possibly stable ternary phases (https://pubs.acs. org/doi/10.1021/acs.chemmater.7b00809).26 In situ NMR spectroscopy may prove even more informative, given its ability to follow specific nuclei during a reaction. The Hu group has carried out live NMR measurements on lithium transition-metal oxide battery cathode materials, collecting spectra as the batteries are charged and discharged (https://pubs.acs.org/ doi/10.1021/acs.chemmater.7b02589).27 This study sheds light on the real-time motion of lithium ions to and from specific sites in the structure, information vital to understanding and optimizing these materials. The local environment around ions is crucial to the performance of battery, fuel-cell, and ferroelectric materials. While commercially available X-ray diffractometers reveal details on the average long-range structure of a solid, local distortionsor very subtle long-range distortionscaused by the ion substitutions or vacancies common to these materials may be missed by this technique. Researchers are now making use of more powerful synchrotron X-ray sources or using neutron or electron diffraction methods. For example, the Ramezanipour and Dolgos groups are studying complex layered perovskite oxides with potential uses as solid oxide fuel-cell electrodes and ferroelectrics. The behavior of compounds such as CaSrFeCoO6−δ (https://pubs.acs.org/doi/10.1021/acs. inorgchem.7b02079)28 and Bi2SrCaTiNb2O12 (https://pubs. acs.org/doi/10.1021/acs.chemmater.7b02151)29 is determined by the mixing of metals on several cation sites, which was analyzed in both cases by combining X-ray and neutron diffraction studies. Pair distribution function (PDF) analysis of the diffraction data is proving to be an increasingly powerful probe of the local structure, as is demonstrated by the study of Na3PS4, a potential sodium-ion battery electrolyte material, by the Zeier group. This compound exhibits cubic and tetragonal polymorphs, but PDF analysis of the synchrotron data reveals that the local environments in both polymorphs are nearly identical; this finding indicates that observed differences in the ionic conductivity between the two polymorphs are likely the result of differences in the defect concentrations (https://pubs. acs.org/doi/10.1021/acs.inorgchem.8b00458).30 Crystallographic studies can also be complemented by the use of NMR, which, as noted earlier, yields information about coordination around specific atoms. The Dutton group use 7Li NMR to confirm the insertion of lithium into the potential battery cathode material MgMnB2O5 and monitor the resulting change in the manganese oxidation state via magnetic susceptibility and electrochemical measurements (https://pubs.acs.org/doi/10. 1021/acs.chemmater.7b00177).31 The work showcased in this Virtual Issue demonstrates the creativity, range, and areas of interest of up-and-coming
synthesizing new topological materials (https://pubs.acs.org/ doi/abs/10.1021/acs.chemmater.7b05133).15 Solid-state chemistry has driven a recent disruptive advance in the field of solar-cell materials. While the seminal work on solarcell development involved the production of p−n junctions in silicon and germanium by the physicists and engineers at AT&T Bell Laboratories in the early 1950s, solid-state chemists have taken it upon themselves to seek improved semiconductors with direct band gaps and high absorption coefficients to compete with the dominance of silicon. Gallium arsenide and cadmium telluride meet these requirements, but they contain toxic elements. The CuIn1−xGaxSe2 family of compounds is promising for thin-film solar cells, but the materials are hindered by difficult vapor deposition production techniques. A more promising and highly active arena for solar-cell materials is the halide perovskite family of compounds. CsPbI3 and hybrid variants containing small organic cations such as MPbI3 (M = methylammonium cation) have direct band gaps in the visible region and can be solution-processed to form thin-film photovoltaics. Like the oxide perovskites, the structures can accommodate different cations, leading to the formation of supercells and layered compounds with modified transport properties. Their structural versatility and tailoring of the optical properties is demonstrated in recent reports by the Karunadasa, Melot, and Neilson groups, pointing out the possibilities and pitfalls of substituting lead with less toxic elements such as tin and bismuth (https://pubs.acs. org/doi/10.1021/acs.inorgchem.6b01336, https://pubs.acs. org/doi/10.1021/acs.inorgchem.6b01571, and https://pubs. acs.org/doi/10.1021/acs.chemmater.7b04516).16−18 Thermoelectrics is another field that has long been dominated by traditional workhorse materials, such as Bi2Te3 and Si/Ge alloys, and has undergone a renaissance in recent years. The advances are largely driven by the discovery and development of semiconducting solids containing rattling atoms and defects that lower the thermal conductivity. The search for tellurium-free solids with high thermoelectric figures of merit has led to an interest in complex metal phosphides and selenides. In one example, the Kovnir group reports on site splitting in the zinc/ phosphorus frameworks of La4Zn7P10 and La4Mg1.5Zn8.5P12 and the effects of this disorder on the electronic properties and thermoelectric performance of these materials (https://pubs. acs.org/doi/10.1021/acs.inorgchem.6b02216).19 Similar studies on Ba2Cr4GeSe10 by Lin, Wu and co-workers suggest that the anisotropic structure, featuring conducting layers alternating with insulating layers, lowers the thermal conductivity of this new material (https://pubs.acs.org/doi/10.1021/acs. inorgchem.7b03002).20 Disorder in the form of doping and substitution has been vital in optimizing the thermoelectric properties of SnSe by Na and K codoping; the Zhao group has found that this tailors the band structure in addition to introducing phonon scattering defects (https://pubs.acs.org/doi/abs/10.1021/jacs.7b05339).21 Deliberate synthetic control of the phonon-scattering defect architecturefrom point defects to dense dislocations to nanoprecipitateswas explored by the Chung group in Pb0.95(Sb0.033□0.017)Se0.6Te0.4 (□ = vacancy), raising the thermoelectric figure of merit considerably (https://pubs.acs. org/doi/abs/10.1021/jacs.8b05741).22 Some strongly anisotropic compounds such as the weak topological insulator BiSe are themselves natural heterostructures, featuring layers of bismuth sandwiched between Bi2Se3 slabs; the Biswas group has confirmed that the ultralow lattice thermal conductivity is the result of localized vibrations of the added bismuth layers and B
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researchers in the field of inorganic solid-state chemistry. Many of these scientists are actively exploring synthesis and characterization techniques that were unknown a scant decade ago. Their discovery and improvements in compounds for solar cells, batteries, and thermoelectric devices will prove crucial in addressing the world’s increasing energy needs. We can anticipate that new inorganic materials coming from their laboratories will drive currently unimaginable technologies. We hope that this collection of Articles demonstrates that the future of this field looks very solid!
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Julia Chan received a B.S. in Chemistry at Baylor University, followed by a Ph.D. under the direction of Prof. Susan Kauzlarich at the University of California at Davis. She then held a National Research Council postdoctoral fellowship at the Materials Science Division of the National Institute of Standards and Technology. She is currently a Professor of Chemistry and Biochemistry at the University of Texas at Dallas and an editor for Science Advances. Her research interest is focused on the crystal growth of highly correlated and quantum materials.
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Susan E. Latturner* Julia Y. Chan*
REFERENCES
(1) Cava, R. J. Oxide Superconductors. J. Am. Ceram. Soc. 2000, 83, 5− 28. (2) Gutfleisch, O.; Willard, M. A.; Brück, E.; Chen, C. H.; Sankar, S. G.; Liu, J. P. Magnetic Materials and Devices for the 21st Century: Stronger, Lighter, and More Energy Efficient. Adv. Mater. 2011, 23, 821−842. (3) Vermeiren, W.; Gilson, J.-P. Impact of Zeolites on the Petroleum and Petrochemical Industry. Top. Catal. 2009, 52, 1131−1161. (4) Whittingham, M. S. Ultimate Limits to Intercalation Reactions for Lithium Batteries. Chem. Rev. 2014, 114, 11414−11443. (5) Tambornino, F.; Sappl, J.; Pultar, F.; Cong, T. M.; Hübner, S.; Giftthaler, T.; Hoch, C. Electrocrystallization: A Synthetic Method for Intermetallic Phases with Polar Metal−Metal Bonding. Inorg. Chem. 2016, 55, 11551−11559. (6) Cox, T.; Gvozdetskyi, V.; Owens-Baird, B.; Zaikina, J. V. Rapid Phase Screening via Hydride Route: A Discovery of K8−xZn18+3xSb16. Chem. Mater.2018. DOI: 10.1021/acs.chemmater.8b04211 (7) Cultrara, N. D.; Wang, Y.; Arguilla, M. Q.; Scudder, M. R.; Jiang, S.; Windl, W.; Bobev, S.; Goldberger, J. E. Synthesis of 1T, 2H, and 6R Germanane Polytypes. Chem. Mater. 2018, 30, 1335−1343. (8) Zhou, X.; Wilfong, B.; Vivanco, H.; Paglione, J.; Brown, C. M.; Rodriguez, E. E. Metastable Layered Cobalt Chalcogenides from Topochemical Deintercalation. J. Am. Chem. Soc. 2016, 138, 16432− 16442. (9) Clarke, S. M.; Amsler, M.; Walsh, J. P. S.; Yu, T.; Wang, Y.; Meng, Y.; Jacobsen, S. D.; Wolverton, C.; Freedman, D. E. Creating Binary Cu−Bi Compounds via High-Pressure Synthesis: A Combined Experimental and Theoretical Study. Chem. Mater. 2017, 29, 5276− 5285. (10) Laniel, D.; Dewaele, A.; Garbarino, G. High Pressure and High Temperature Synthesis of the Iron Pernitride FeN2. Inorg. Chem. 2018, 57, 6245−6251. (11) Mayo, M.; Morris, A. J. Structure Prediction of Li−Sn and Li−Sb Intermetallics for Lithium-Ion Batteries Anodes. Chem. Mater. 2017, 29, 5787−5795. (12) Mansouri Tehrani, A.; Oliynyk, A. O.; Parry, M.; Rizvi, Z.; Couper, S.; Lin, F.; Miyagi, L.; Sparks, T. D.; Brgoch, J. Machine Learning Directed Search for Ultraincompressible, Superhard Materials. J. Am. Chem. Soc. 2018, 140, 9844−9853. (13) Schmiegel, J.-P.; Block, T.; Gerke, B.; Fickenscher, T.; Touzani, R. S.; Fokwa, B. P. T.; Janka, O. EuAu3Al2: Crystal and Electronic Structures and Spectroscopic, Magnetic, and Magnetocaloric Properties. Inorg. Chem. 2016, 55, 9057−9064. (14) Shankhari, P.; Zhang, Y.; Stekovic, D.; Itkis, M. E.; Fokwa, B. P. T. Unexpected Competition between Antiferromagnetic and Ferromagnetic States in Hf2MnRu5B2: Predicted and Realized. Inorg. Chem. 2017, 56, 12674−12677. (15) Schoop, L. M.; Pielnhofer, F.; Lotsch, B. V. Chemical Principles of Topological Semimetals. Chem. Mater. 2018, 30, 3155−3176. (16) Bass, K. K.; Estergreen, L.; Savory, C. N.; Buckeridge, J.; Scanlon, D. O.; Djurovich, P. I.; Bradforth, S. E.; Thompson, M. E.; Melot, B. C. Vibronic Structure in Room Temperature Photoluminescence of the Halide Perovskite Cs3Bi2Br9. Inorg. Chem. 2017, 56, 42−45. (17) Maughan, A. E.; Ganose, A. M.; Candia, A. M.; Granger, J. T.; Scanlon, D. O.; Neilson, J. R. Anharmonicity and Octahedral Tilting in Hybrid Vacancy-Ordered Double Perovskites. Chem. Mater. 2018, 30, 472−483.
AUTHOR INFORMATION
Corresponding Authors
*E-mail:
[email protected]. *E-mail:
[email protected]. ORCID
Susan E. Latturner: 0000-0002-6146-5333 Julia Y. Chan: 0000-0003-4434-2160 Notes
Views expressed in this editorial are those of the authors and not necessarily the views of the ACS. Biographies
Susan Latturner received her undergraduate degree in Chemistry from the University of Virginia and carried out her Ph.D. research at the University of California at Santa Barbara under the direction of Galen Stucky. After postdoctoral work in the Kanatzidis group, she joined the faculty at Florida State University, where she is a professor of inorganic solid-state chemistry. Her research group investigates metal flux synthesis of intermetallic compounds and refractory actinide materials.
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(18) Slavney, A. H.; Smaha, R. W.; Smith, I. C.; Jaffe, A.; Umeyama, D.; Karunadasa, H. I. Chemical Approaches to Addressing the Instability and Toxicity of Lead−Halide Perovskite Absorbers. Inorg. Chem. 2017, 56, 46−55. (19) Wang, J.; Lee, K.; Kovnir, K. Synthesis, Crystal Structure, and Properties of La4Zn7P10 and La4Mg1.5Zn8.5P12. Inorg. Chem. 2017, 56, 783−790. (20) Chen, H.; Chen, Y.-K.; Lin, H.; Shen, J.-N.; Wu, L.-M.; Wu, X.-T. Quaternary Layered Semiconductor Ba2Cr4GeSe10: Synthesis, Crystal Structure, and Thermoelectric Properties. Inorg. Chem. 2018, 57, 916− 920. (21) Ge, Z.-H.; Song, D.; Chong, X.; Zheng, F.; Jin, L.; Qian, X.; Zheng, L.; Dunin-Borkowski, R. E.; Qin, P.; Feng, J.; Zhao, L.-D. Boosting the Thermoelectric Performance of (Na,K)-Codoped Polycrystalline SnSe by Synergistic Tailoring of the Band Structure and Atomic-Scale Defect Phonon Scattering. J. Am. Chem. Soc. 2017, 139, 9714−9720. (22) Zhou, C.; Lee, Y. K.; Cha, J.; Yoo, B.; Cho, S.-P.; Hyeon, T.; Chung, I. Defect Engineering for High-Performance n-Type PbSe Thermoelectrics. J. Am. Chem. Soc. 2018, 140, 9282−9290. (23) Samanta, M.; Pal, K.; Pal, P.; Waghmare, U. V.; Biswas, K. Localized Vibrations of Bi Bilayer Leading to Ultralow Lattice Thermal Conductivity and High Thermoelectric Performance in Weak Topological Insulator n-Type BiSe. J. Am. Chem. Soc. 2018, 140, 5866−5872. (24) Kanatzidis, M. G. Discovery-Synthesis, Design, and Prediction of Chalcogenide Phases. Inorg. Chem. 2017, 56, 3158−3173. (25) Shoemaker, D. P.; Hu, Y.-J.; Chung, D. Y.; Halder, G. J.; Chupas, P. J.; Soderholm, L.; Mitchell, J. F.; Kanatzidis, M. G. In Situ Studies of a Platform for Metastable Inorganic Crystal Growth and Materials Discovery. Proc. Natl. Acad. Sci. U. S. A. 2014, 111, 10922−10927. (26) Bhutani, A.; Schiller, J. A.; Zuo, J. L.; Eckstein, J. N.; Greene, L. H.; Chaudhuri, S.; Shoemaker, D. P. Combined Computational and in Situ Experimental Search for Phases in an Open Ternary System, Ba− Ru−S. Chem. Mater. 2017, 29, 5841−5849. (27) Li, X.; Tang, M.; Feng, X.; Hung, I.; Rose, A.; Chien, P.-H.; Gan, Z.; Hu, Y.-Y. Lithiation and Delithiation Dynamics of Different Li Sites in Li-Rich Battery Cathodes Studied by Operando Nuclear Magnetic Resonance. Chem. Mater. 2017, 29, 8282−8291. (28) Hona, R. K.; Huq, A.; Ramezanipour, F. Unraveling the Role of Structural Order in the Transformation of Electrical Conductivity in Ca2FeCoO6−δ, CaSrFeCoO6−δ, and Sr2FeCoO6−δ. Inorg. Chem. 2017, 56, 14494−14505. (29) Surta, T. W.; Manjón-Sanz, A.; Qian, E. K.; Mansergh, R. H.; Tran, T. T.; Fullmer, L. B.; Dolgos, M. R. Dielectric and Ferroelectric Properties in Highly Substituted Bi2Sr(A)TiNb2O12 (A = Ca2+, Sr2+, Ba2+) Aurivillius Phases. Chem. Mater. 2017, 29, 7774−7784. (30) Krauskopf, T.; Culver, S. P.; Zeier, W. G. Local Tetragonal Structure of the Cubic Superionic Conductor Na3PS4. Inorg. Chem. 2018, 57, 4739−4744. (31) Glass, H. F. J.; Liu, Z.; Bayley, P. M.; Suard, E.; Bo, S.-H.; Khalifah, P. G.; Grey, C. P.; Dutton, S. E. MgxMn2−xB2O5 Pyroborates (2/3 ≤ x ≤ 4/3): High Capacity and High Rate Cathodes for Li-Ion Batteries. Chem. Mater. 2017, 29, 3118−3125.
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DOI: 10.1021/acs.inorgchem.8b03382 Inorg. Chem. XXXX, XXX, XXX−XXX
