Spinel and post-spinel phase assemblages in Zn₂TiO₄: an experimental and theoretical study

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• 作者：Yanyao Zhang ; Xi Liu ; Sean R. Shieh ; Xinjian Bao…
• 关键词：Compressibility ; DFT calculations ; Diamond ; anvil cell ; High ; P phase transition ; Synchrotron X ; ray diffraction ; Zn2TiO4 ; CT ; Zn2TiO4 ; Sp
• 刊名：Physics and Chemistry of Minerals
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：44
• 期：2
• 页码：109-123
• 全文大小：
• 刊物类别：Earth and Environmental Science
• 刊物主题：Mineralogy; Crystallography and Scattering Methods; Geochemistry; Mineral Resources;
• 出版者：Springer Berlin Heidelberg
• ISSN：1432-2021
• 卷排序：44

文摘

Zn₂TiO₄ spinel (Zn₂TiO₄-Sp) was synthesized by a solid-state reaction method (1573 K, room P and 72 h) and quasi-hydrostatically compressed to ~24 GPa using a DAC coupled with a synchrotron X-ray radiation (ambient T). We found that the Zn₂TiO₄-Sp was stable up to ~21 GPa and transformed to another phase at higher P. With some theoretical simulations, we revealed that this high-P phase adopted the CaTi₂O₄-type structure (Zn₂TiO₄-CT). Additionally, the isothermal bulk modulus (K_T) of the Zn₂TiO₄-Sp was experimentally obtained as 156.0(44) GPa and theoretically obtained as 159.1(4) GPa, with its first pressure derivative \(K_{\text{T}}^{'}\) as 3.8(6) and 4.37(4), respectively. The volumetric and axial isothermal bulk moduli of the Zn₂TiO₄-CT were theoretically obtained as K_T = 150(2) GPa (\(K_{\text{T}}^{'}\) = 5.4(2); for the volume), K_T-a = 173(2) GPa (\(K_{{\text{T-}}a}^{'}\) = 3.9(1); for the a-axis), K_T-b = 74(2) GPa (\(K_{{\text{T-}}b}^{'}\) = 7.0(2); for the b-axis), and K_T-c = 365(8) GPa (\(K_{{\text{T-}}c}^{'}\) = 1.5(4); for the c-axis), indicating a strong elastic anisotropy. The Zn₂TiO₄-CT was found as ~10.0 % denser than the Zn₂TiO₄-Sp at ambient conditions. The spinel and post-spinel phase assemblages for the Zn₂TiO₄ composition at high T have been deduced as Zn₂TiO₄-Sp, ZnTiO₃-ilmenite + ZnO-wurtzite, ZnTiO₃-ilmenite + ZnO-rock salt, ZnTiO₃-perovskite + ZnO-rock salt, and Zn₂TiO₄-CT as P increases, which presumably implies a potential stability field for a CT-type Mg₂SiO₄ at very high P.