中文摘要：

MgSiO3钙钛矿是地球下地幔中含量最丰富的物质,通常仅在高于22GPa的压力下才能稳定存在,研究其单晶性质非常困难。实验合成MgSiO3钙钛矿,尤其是大颗粒单晶,对于研究下地幔的性质极其重要。利用川井型多砧实验装置,在25GPa和1 500℃的条件下合成了大颗粒MgSiO3钙钛矿单晶。通过对比不同长度样品容器的实验结果发现,即使在较长容器底端的大温度梯度区也可长出大颗粒的晶体,这与前人的实验结果不同。认为大温度梯度虽然可造成高结晶核密度,但也可以提高晶体生长的驱动力,使晶体更快生长,而且较长的容器可以增加晶体的产量。另外,还从孪晶的角度分析了MgSiO3钙钛矿的生长机制,对进一步认识和理解高压下MgSiO3钙钛矿晶体的生长特性有重要意义。

英文摘要：

MgSiO3 perovskite is the most abundant material in the Earth＇s lower mantle. It is very difficult to obtain single crystal of MgSiO3 perovskite due to its high pressure stability over 22 GPa. Thus synthesis of MgSiO3 perovskite, especially the large grain size single crystal, is extremely important to investigate the properties of lower mantle. In this study, the details of synthesizing the single crystal of MgSiOa perovskite with large grain size were presented. Our synthesis experiments were conducted at a condition of 25 GPa and 1 500 ℃ using a 5 000 t Kawai-type multi-anvil apparatus. The results using different lengths of Pt capsule showed the large grain size perovskite crystal can also be obtained even at the large temperature gradient area in longer Pt capsule,which is different from previous experimental results. It is suggested that a large temperature gradient in the sample capsule can increase the nucleation density, however, it can also boost the crystal growth of perovskite and thus crystal can grow at a fast speed. Furthermore,the perovskite growth mechanism was investigated through analysis of twin crystal, which is important to understand the characteristics of the crystal growth of MgSiO3 perovskite at high pressures.