Department of Chemistry, University of Houston, 136 Fleming Building, Houston, Texas 77204-5003, USA.
Inorg Chem. 2011 Jun 6;50(11):5215-22. doi: 10.1021/ic200511q. Epub 2011 May 10.
Two new noncentrosymmetric (NCS) polar oxide materials, Zn(2)(MoO(4))(AO(3)) (A = Se(4+) or Te(4+)), have been synthesized by hydrothermal and solid-state techniques. Their crystal structures have been determined, and characterization of their functional properties (second-harmonic generation, piezoelectricity, and polarization) has been performed. The isostructural materials exhibit a three-dimensional network consisting of ZnO(4), ZnO(6), MoO(4), and AO(3) polyhedra that share edges and corners. Powder second-harmonic generation (SHG) measurements using 1064 nm radiation indicate the materials exhibit moderate SHG efficiencies of 100 × and 80 × α-SiO(2) for Zn(2)(MoO(4))(SeO(3)) and Zn(2)(MoO(4))(TeO(3)), respectively. Particle size vs SHG efficiency measurements indicate the materials are type 1 non-phase-matchable. Converse piezoelectric measurements resulted in d(33) values of ∼14 and ∼30 pm/V for Zn(2)(MoO(4))(SeO(3)) and Zn(2)(MoO(4))(TeO(3)), respectively, whereas pyroelectric measurements revealed coefficients of -0.31 and -0.64 μC/m(2) K at 55 °C for Zn(2)(MoO(4))(SeO(3)) and Zn(2)(MoO(4))(TeO(3)), respectively. Frequency-dependent polarization measurements confirmed that all of the materials are nonferroelectric; that is, the macroscopic polarization is not reversible, or "switchable". Infrared, UV-vis, thermogravimetric, and differential thermal analysis measurements were also performed. First-principles density functional theory (DFT) electronic structure calculations were also done. Crystal data: Zn(2)(MoO(4))(SeO(3)), monoclinic, space group P2(1) (No. 4), a = 5.1809(4) Å, b = 8.3238(7) Å, c = 7.1541(6) Å, β = 99.413(1)°, V = 305.2(1) Å(3), Z = 2; Zn(2)(MoO(4))(TeO(3)), monoclinic, space group P2(1) (No. 4), a = 5.178(4) Å, b = 8.409(6) Å, c = 7.241(5) Å, β = 99.351(8)°, V = 311.1(4) Å(3), Z = 2.
两种新的非中心对称（NCS）极性氧化物材料 Zn(2)(MoO(4))(AO(3))（A=Se(4+)或 Te(4+)）已通过水热和固态技术合成。它们的晶体结构已被确定，并对其功能特性（二次谐波产生、压电性和极化）进行了表征。同构材料表现出由 ZnO(4)、ZnO(6)、MoO(4)和 AO(3)多面体组成的三维网络，这些多面体共享边缘和角。使用 1064nm 辐射的粉末二次谐波产生（SHG）测量表明，这些材料表现出适度的 SHG 效率，分别为 100×和 80×α-SiO(2)的 Zn(2)(MoO(4))(SeO(3))和 Zn(2)(MoO(4))(TeO(3))。粒径与 SHG 效率的测量表明，这些材料是 1 型非相位匹配的。逆压电测量得到的 Zn(2)(MoO(4))(SeO(3))和 Zn(2)(MoO(4))(TeO(3))的 d(33)值分别约为 14 和 30 pm/V，而热释电测量在 55°C 下得到 Zn(2)(MoO(4))(SeO(3))和 Zn(2)(MoO(4))(TeO(3))的系数分别为-0.31 和-0.64 μC/m(2)K。频率相关极化测量证实所有材料均是非铁电的；也就是说，宏观极化不是可逆的，或者说是“可切换的”。还进行了红外、紫外-可见、热重和差示热分析测量。还进行了第一性原理密度泛函理论（DFT）电子结构计算。晶体数据：Zn(2)(MoO(4))(SeO(3))，单斜，空间群 P2(1)（No.4），a=5.1809(4)Å，b=8.3238(7)Å，c=7.1541(6)Å，β=99.413(1)°，V=305.2(1)Å(3)，Z=2；Zn(2)(MoO(4))(TeO(3))，单斜，空间群 P2(1)（No.4），a=5.178(4)Å，b=8.409(6)Å，c=7.241(5)Å，β=99.351(8)°，V=311.1(4)Å(3)，Z=2。
