Article Cite This: Chem. Mater. 2018, 30, 1045−1054 pubs.acs.org/cm ‑ YCrWO6: Polar and Magnetic Oxide with CaTa2O6 Related Structure † † ‡ § ∥ ⊥ Sun Woo Kim, Thomas J. Emge, Zheng Deng, Ritesh Uppuluri, Liam Collins, Saul H. Lapidus, # ∇ ‡ ○ ∥ Carlo U. Segre, Mark Croft, Changqing Jin, Venkatraman Gopalan, Sergei V. Kalinin, † and Martha Greenblatt*, † Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, 610 Taylor Road, Piscataway, New Jersey 08854, United States ‡ Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China § Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802, United States ∥ Center for Nanophase Material Science & Institute for Functional Imaging Materials, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States ⊥ Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, United States # Department of Physics, and Center for Synchrotron Radiation Research and Instrumentation, Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, Illinois 60616, United States ∇ Department of Physics and Astronomy, Rutgers, The State University of New Jersey, 136 Frelinghusen Road, Piscataway, New Jersey 08854, United States ○ Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, United States *S Supporting Information ABSTRACT: A new polar and magnetic oxide, YCrWO6, was successfully synthesized and characterized. YCrWO6 crystallizes in polar orthorhombic space group Pna21 (no. 33) of edge- sharing dimers of CrO6 and WO6 octahedra, which are connected by corner-sharing to form a three-dimensional framework structure with Y3+ cations located in the channels. The structure of YCrWO6 is related to that of CaTa2O6; however, the ordering of Cr3+ and W6+ in the octahedral sites breaks the inversion symmetry of the parent CaTa2O6 structure. X-ray absorption near edge spectroscopy of fi 3+ 6+ YCrWO6 con rmed the oxidation state of Cr and W . Temperature-dependent optical second harmonic generation fi measurements on YCrWO6 con rmed the noncentrosymmetric character and evidenced a noncentrosymmetric-to- ° centrosymmetric phase transition above 800 C. Piezoresponse force microscopy measurements on YCrWO6 at room temperature show strong piezoelectric domains. Magnetic measurements of YCrWO6 indicate antiferromagnetic order at TN of ∼22 K with Weiss temperature of −34.66 K. ■ INTRODUCTION oxygen octahedral rotation in perovskites or layered perov- 21−23 Polar and magnetic oxide materials are investigated intensely, skites. However, it is still a challenge to design and to because of their fundamentally interesting and useful physical synthesize new polar and magnetic oxide materials with optimal properties such as ferroelectricity, pyroelectricity, piezoelec- characteristics. − ′ tricity, multiferroicity, and magnetoelectricity,1 5 all important Our earlier study on PbSb2O6-related materials (ABB O6) − ′ for potential applications in advanced devices.6 9 Several demonstrated that by ordering or rearrangement of the B/B strategies along with first-principles calculations have been cations the inversion symmetry of the parent compound could proposed and investigated to search for new polar and magnetic be broken (e.g., P31̅m, no. 162 → P312, no. 149, or P62̅m, no. 24−26 oxides including the following: (1) the combination of stereo 189). Similarly, in our search for new multiferroic active lone pair (6s2) cations (Tl+,Pb2+,Bi3+) and/or second- materials we have considered new structural phases where order Jahn−Teller (SOJT) d0 cations (Ti4+,Nb5+,Mo6+,W6+, 10−13 etc.) with magnetic cations, (2) the substitution of Received: November 25, 2017 magnetic cations in parent polar structures (e.g., LiNbO3-type Revised: January 2, 2018 14−20 or Ni3TeO6-type, etc.), and (3) octahedral tilting or Published: January 5, 2018 © 2018 American Chemical Society 1045 DOI: 10.1021/acs.chemmater.7b04941 Chem. Mater. 2018, 30, 1045−1054 Chemistry of Materials Article cation ordering/rearrangement might lead to breaking of the should be good candidates for designing new polar magnetic center of symmetry. The crystal structure of aeschynite-type oxide materials, if substitution of magnetic cations (3d−5d ′ materials (general formula, LnMM O6) exhibits a CaTa2O6- transition metals) into the crystal structure are possible. 27 related structure (space group, SG: Pnma, no. 62) consisting Previously, LnMWO6 (M = V, Cr, Fe) were proposed to ′ 3+ 6+ of edge-sharing dimers of [(M,M )O6] octahedra connected by exhibit an ordered arrangement of M and W with polar corner-sharing to form a three-dimensional framework space group, Pna21 (no. 33); however, this study did not structure with the Ln3+ ions located in the channels (Figure provide any detailed structure information and physical 28,29 4+ 5+ 34 1). Aeschynite-type materials, Ln(Ti M )O6 (Ln = La, properties. Recently, Ghara et al. reported ordered aeschynite-type polar magnets, RFeWO6 (R = Dy, Eu, Tb, and Y), with type-II multiferroic behavior.35 Based on this observation, we focused our efforts to find new polar and magnetic oxide materials with CaTa2O6-related structures through exploratory synthesis. Here we report the successful synthesis, crystal growth, and characterization of the CaTa2O6-related new polar and magnetic oxide, YCrWO6, and the investigation of its crystal structure−properties relation- ships. Cation ordering of Cr3+ and W6+ was expected, because of the charge difference of Cr3+/W6+ as well as the SOJT character of W6+ in an octahedral environment. ■ EXPERIMENTAL SECTION Figure 1. Ball-and-stick structure of CaTa2O6-related materials: (a) 27 4+ 5+ Reagents. Y2O3 (Alfa Aesar, 99.99%), Cr2O3 (Alfa Aesar, 99.97%), CaTa2O6 in the ab-plane (left) and (b) Ln(Ti M )O6 (Ln = La to 28−33 and WO3 (Alfa Aesar, 99.8%) were used without any further Dy; M = Nb or Ta) in the ab-plane (right). fi ° puri cation. Y2O3 was preheated at 950 C for overnight before use. Synthesis. Polycrystalline YCrWO6 was prepared by a conven- Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Dy; M = Nb or Ta) have been tional solid state reaction. Stoichiometric amounts of Y2O3 (0.3387 g, 1.5 mmol), Cr O (0.2280 g, 1.5 mmol), and WO (0.6955 g, 3.0 investigated due to their microwave dielectric properties as well 2 3 3 30−33 mmol) were thoroughly ground and pressed into a pellet. The pellet as for phosphor applications. In aeschynite-type ° ′ ′ was placed on Pt foil in an alumina boat and treated at 1150 C for 12 LnMM O6, if M and M are ordered, their crystal structure h in air, then reground into fine powder, pressed into a pellet again, will adopt lower symmetry polar space group, Pna21 (no. 33), and heated to 1150 °C for 12 h, and then cooled to room temperature due to symmetry constraints. Hence these types of materials (the heating and cooling rate was 200 °C/h, respectively). Brown- fi Table 1. Crystal Data and Structure Re nement for YCrWO6 formula weight 420.76 temperature 293(2) K wavelength 0.71073 Å crystal system orthorhombic space group Pna21 (no. 33) unit cell dimensions a = 10.8675(8) Å, α =90° b = 5.1633(4) Å, β =90° c = 7.3072(5) Å, γ =90° volume 410.02(5) Å3 Z 4 density (calculated) 6.816 Mg/m3 absorption coefficient 44.559 mm−1 F(000) 740 crystal size 0.140 × 0.070 × 0.020 mm3 θ range for data collection 3.750−32.603° index ranges −16 ≤ h ≤ 15, −7 ≤ k ≤ 7, −11 ≤ l ≤ 11 reflections collected 5424 independent reflections 1483 [R(int) = 0.0329] completeness to θ = 25.242° 100.0% absorption correction numerical max and min transmission 0.660 13 and 0.018 37 refinement method full-matrix least-squares on F2 data/restraints/parameters 1483/13/84 goodness-of-fitonF2 1.114 final R indices [I >2σ(I)] R1 = 0.0200, wR2 = 0.0417 R indices (all data) R1 = 0.0211, wR2 = 0.0420 absolute structure parameter 0.43(2) extinction coefficient 0.0021(2) largest difference peak and hole 1.634 and −2.216 e.Å−3 1046 DOI: 10.1021/acs.chemmater.7b04941 Chem. Mater. 2018, 30, 1045−1054 Chemistry of Materials Article Table 2. Atomic Coordinates and Displacement Parameter for YCrWO6 ff 2 * atom Wycko position xyzUeq (Å ) Y(1) 4a 0.543 23(7) 0.954 56(13) 0.5213(2) 0.005 32(14) Cr(1) 4a 0.367 42(10) 0.5466(2) 0.7727(8) 0.0042(2) W(1) 4a 0.353 14(2) 0.556 52(4) 0.277 12(2) 0.004 37(8) O(1) 4a 0.3805(5) 0.6705(10) 0.5187(9) 0.0055(9) O(2) 4a 0.2138(5) 0.3840(11) 0.3354(8) 0.0052(10) O(3) 4a 0.2910(5) 0.8743(11) 0.2063(8) 0.0056(11) O(4) 4a 0.5256(5) 0.7301(11) 0.8141(7) 0.0050(11) O(5) 4a 0.3574(5) 0.4400(10) 0.0289(10) 0.0065(11) O(6) 4a 0.4779(5) 0.2541(11) 0.7313(7) 0.0049(11) colored YCrWO6 polycrystalline powder was obtained, and the purity Table 3. Selected Bond Distances, Angles, and Bond of sample was confirmed by powder X-ray diffraction (XRD). Valences Sum (BVS) for YCrWO6 Crystal Growth. Crystals of YCrWO6 were grown from Li2CO3/ fl B2O3 ux. The starting materials (YCrWO6:Li2CO3:B2O3 = 3:5:5) cation anion bond length (Å) BVS were mixed and placed in a Pt crucible, heated at 1200 °C for 24 h, 3+ ° ° Y(1) O(1) 2.298(6) 3.16 (Y ) cooled slowly to 950 C (rate: 2 C/h), and then cooled to room O(2) 2.445(6) temperature (rate: 100 °C/h). Most of the flux evaporated, and the O(3) 2.419(6) products were washed with distilled water and ethanol aided by sonication and isolated by vacuum filtration.