P-V equation of State, thermal expansion, and P-T stability of synthetic zincochromite (ZnCr2O4 spinel)
P-V equation of State, thermal expansion, and P-T stability of synthetic zincochromite (ZnCr2O4 spinel)
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DOI：
10.2138/am.2005.1755
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发表时间：
2005-07
影响因子：
3.1
通讯作者：
D. Levy;V. Diella;A. Pavese;M. Dapiaggi;A. Sani
中科院分区：
文献类型：
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作者：
D. Levy;V. Diella;A. Pavese;M. Dapiaggi;A. Sani
摘要采用室温高压（0.0001.21 GPa）同步辐射粉末衍射数据和高温（298.1240 K）粉末衍射数据相结合的方法，研究了合成锌铬铁矿（ZnCr 2 O 4）的弹性性质和热行为。通过将两个状态方程（EoS）拟合到P-V数据来获得弹性性质。三阶Birch-Murnaghan模型的结果与Vinet EoS的结果一致，得出：K 0 = 183.1（±3.5）GPa，K' = 7.9（±0.6），K“= 0.1278 GPa-1（隐含值），V0 = 577.8221 μ 3（固定值）。锌铬铁矿不表现出有序无序反应，在高温下的热范围内探索，与以前的研究。用αV = α0 + α 1 T + α2/T-2对体积热膨胀进行建模，其中只有第一个系数显著[α0 = 23.0（4）10- 6 K-1]。在23 GPa以上的衍射图案暗示相变的开始;高压相在约30 GPa下观察到，并表现出正交对称性。然后，利用锌铬铁矿的弹性和热性质，通过热力学计算模拟ZnCr 2 O 4相对于其氧化物成分（Cr2 O3和类岩盐ZnO）的P-T稳定性场。尖晶石预计在约18 GPa和室温下分解成氧化物，没有缓慢的动力学。
Abstract The elastic properties and thermal behavior of synthetic zincochromite (ZnCr2O4) have been studied by combining room-temperature high-pressure (0.0001.21 GPa) synchrotron radiation powder diffraction data with high-temperature (298.1240 K) powder diffraction data. Elastic properties were obtained by fitting two Equations of State (EoS) to the P-V data. A third-order Birch-Murnaghan model, which provides results consistent with those from the Vinet EoS, yields: K0 = 183.1(±3.5) GPa, K’ = 7.9(±0.6), K’’ = .0.1278 GPa-1 (implied value), at V0 = 577.8221 Å3 (fixed). Zincochromite does not exhibit order-disorder reactions at high temperature in the thermal range explored, in agreement with previous studies. The volume thermal expansion was modeled with αV = α0 + α1T + α2/T-2, where only the first coefficient was found to be significant [α0 = 23.0(4) 10-6K-1]. Above 23 GPa diffraction patterns hint at the onset of a phase transition; the high pressure phase is observed at approximately 30 GPa and exhibits orthorhombic symmetry. The elastic and thermal properties of zincochromite were then used to model by thermodynamic calculations the P-T stability field of ZnCr2O4 with respect to its oxide constituents (Cr2O3 and rocksalt-like ZnO). Spinel is expected to decompose into oxides at about 18 GPa and room temperature, in absence of sluggish kinetics.