DCITIMAC , Universidad de Cantabria , Avenida Los Castros 48 , 39005 Santander , Spain.
Departament de Física Aplicada , Universitat de València , Dr. Moliner 50 , 46100 Burjassot , Spain.
Inorg Chem. 2018 Nov 5;57(21):14005-14012. doi: 10.1021/acs.inorgchem.8b01808. Epub 2018 Oct 29.
The zircon to scheelite phase boundary of ErVO has been studied by high-pressure and high-temperature powder and single-crystal X-ray diffraction. This study has allowed us to delimit the best synthesis conditions of its scheelite-type phase, determine the ambient-temperature equation of state of the zircon and scheelite-type structures, and obtain the thermal equation of state of the zircon-type polymorph. The results obtained with powder samples indicate that zircon-type ErVO transforms to scheelite at 8.2 GPa and 293 K and at 7.5 GPa and 693 K. The analyses yield bulk moduli K of 158(13) GPa for the zircon phase and 158(17) GPa for the scheelite phase, with a temperature derivative of d K/d T = -[3.8(2)] × 10 GPa K and a volumetric thermal expansion of α = [0.9(2)] × 10 K for the zircon phase according to the Berman model. The results are compared with those of other zircon-type vanadates, raising the need for careful experiments with highly crystalline scheelite to obtain reliable bulk moduli of this phase. Finally, we have performed single-crystal diffraction experiments from 110 to 395 K, and the obtained volumetric thermal expansion (α) for zircon-type ErVO in the 300-395 K range is [1.4(2)] × 10 K, in good agreement with previous data and with our experimental value given from the thermal equation of state fit within the limits of uncertainty.
采用高压高温粉末和单晶 X 射线衍射研究了 ErVO 的锆石-白钨矿相界。这项研究使我们能够限定其白钨矿型相的最佳合成条件，确定锆石和白钨矿型结构的环境温度状态方程，并获得锆石型多晶型的热状态方程。粉末样品的结果表明，锆石型 ErVO 在 8.2 GPa 和 293 K 以及 7.5 GPa 和 693 K 下转变为白钨矿。分析得出，锆石相的体弹模量 K 为 158(13)GPa，白钨矿相为 158(17)GPa，根据 Berman 模型，温度导数 d K/d T = -[3.8(2)] × 10 GPa K，体积热膨胀率α为锆石相的 [0.9(2)] × 10 K。结果与其他锆石型钒酸盐进行了比较，这就需要用高度结晶的白钨矿进行仔细的实验，以获得该相的可靠体弹模量。最后，我们在 110 至 395 K 之间进行了单晶衍射实验，在 300 至 395 K 范围内，锆石型 ErVO 的体积热膨胀率 (α) 为 [1.4(2)] × 10 K，与之前的数据和我们在热状态方程范围内拟合的实验值一致，误差在可接受范围内。
