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Stability Field of Baddeleyite (ZrO_2) and Its Change Due to Additive

斜锆石(ZrO_2)的稳定场及其随添加剂的变化

基本信息

批准号：
01540658
负责人：
KUME S.
金额：
$ 0.83万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1990
项目状态：
已结题

项目摘要

The mineral baddeleyite, ZrO_2 is known to have three polymorphs in high temperature, monoclinic, tetragonal, cubic and two in high pressure, orthorhombic I and II. Since some of these phases are not quenchable to ambient conditions of temperature and pressure, uncertainties have been left unsolved on their equilibrium relations. The present experiment was performed with the aim to determine the stability fields of ortho I and II phases and to clear the influence of additives on these fields. The obtained results are summarized as follows : 1. Starting materials with different grain sizes were treated at 400^ﾟC・6GPa and only the finest grains was found to be quenched. In situ observation using a diamond anvil cell revealed that the transition pressure from monoclinic to ortho I phases shifted towards higher pressure side as the grain size decreased, indicating a clear size effect. 2. Quenched sample of ortho I and II phases were submitted to thermodynamical experiments in which measurements of bulk modulus, thermal expansion and heat of formation were included. When these data were combined to the equilibrium values of temperature-pressure of adjacent two phases obtained by the synthesis, the phase boundaries between monoclinic and ortho I and also between ortho I and II were drawn, that is, T (^ﾟC) = 335 - 102P (GPa) (fine grain) and T (^ﾟC) = 300P (GPa) - 4300 respectively. 3. A sample, which contained 2mo1%Y_2O_3, were prepared to invest igate change of stability relations among the phases. This starting material consisted of monoclinic and tetragonal phases. When it was compressed, only monoclinic phases converted to ortho I. In the case of higher pressure, the sample was found to transform to cotunnite-type completely and no tetra gonal phase remained.

斜锆石ZrO_2在高温下有三种晶型，即单斜晶型、四方晶型和立方晶型，在高压下有两种晶型，即斜方晶I型和斜方晶II型。由于这些相中的一些相在环境温度和压力条件下是不能淬火的，因此它们的平衡关系的不确定性一直没有得到解决。本实验的目的是确定的邻I和II相的稳定领域，并清除这些领域的添加剂的影响。主要研究结果如下：1.在400 ℃·6 GPa下处理不同晶粒尺寸的起始材料，发现只有最细的晶粒被淬火。使用金刚石对顶砧单元的原位观察显示，从单斜相到邻I相的转变压力随着晶粒尺寸的减小而向高压侧移动，表明明显的尺寸效应。2.对淬火后的邻位I和II相样品进行了体积模量、热膨胀和生成热的测量。将这些数据与通过合成得到的相邻两相的温度-压力平衡值相结合，绘制出单斜晶与邻位I以及邻位I与邻位II之间的相界，分别为T（^C）= 335 - 102 P（GPa）（细晶）和T（^C）= 300 P（GPa）- 4300。3.制备了含2mo1%Y_2O_3的样品，考察了各相稳定性关系的变化。该起始材料由单斜晶相和四斜晶相组成。当它被压缩时，只有单斜相转变为正I相。在较高压力下，样品完全转变为钴钨石型，无四方相残留。