AlPO4高温高压相变研究

利用配有电阻炉外加热装置的金刚石对顶砧及紧装式六面顶高压容器,在500—1700℃和常压至17.8GPa温压范围内,对AlPO₄进行了实验研究。常压下,磷铝石(石英型AlPO₄)向鳞石英型AlPO₄转变的温度约为778℃,鳞石英型向方英石型AlPO₄转变的温度约为1100℃,块磷铝石α-β相转变的温度为586℃。在5.4 GPa和1300℃以下,块磷铝石保持稳定,在5GPa和大于1700℃时,发现AlPO₄分解为Al₂O₃,(刚玉)和P₂O₅鳞石英型AlPO₄在6GPa及500℃转变成斜方晶系新相,新相在室温常压下的晶胞参数为:a=4.930Å,b=7.200Å和c=6.165Å,鳞石英型AlPO₄及块磷铝石在11GPa以上均变为NiSO₄型结构。文中讨论了AlPO₄与SiO₂的异同,并给出了一个AlPO₄可能的相图。

AN INVESTIGATION OF THE PHASE TRANSFORMATION OF AIPO, AT HIGH PRESSURE AND HIGH TEMPERATURE

By using the diamond-anvil pressure cell coupled with resistant-wire heating and the six anvil pressure vessel, the phase transformation of AlPO₄ has been investigated at pressures up to -17.8 GPa and at temperatures from 500℃ to 1700℃. Under atmospheric pressure, the transition temperature from berlinite (qurtze-type AlPO₄) to tridymite-type structure is about 778℃, and from tridymite-type to cristobalite-type structure-about 1100℃. Theα-β transition of berlinite takes place at 586℃. Berlinite is stable at pressures below 5.5 GPa and temperatures below 1300℃. It decomposes into the mixture of Al₂O₃ (Corundum) plus P₂O₅ at 5 GPa and over 1700℃. Tridymite-type AlPO₄ is found to transform to a new phase at 6 GPa and 500℃. The new phase has been indexed on the basis of an orthorhombic cell with lattice parameters of a=4.930, b=7.200, c=6.165Å at room temperature and atmospheric pressure. At pressures greater than 11 GPa, AlPO₄ transforms from berlinite or tridymite-type to NiSO₄-type form. A possible P-T phase diagram of AlPO₄ is given in this paper.