Thermoelastic properties of the high-pressure phase of SnO2 determined by in situ X-ray observations up to 30 GPa and 1400 K

In situ synchrotron X-ray experiments in the system SnO2 were made at press ures of 4-29 GPa and temperatures of 300-1400 K using sintered diamond anvi ls in a 6-8 type high-pressure apparatus. Orthorhombic phase (alpha -PbO2 s tructure) underwent a transition to a cubic phase (Pa (3) over bar structur e) at 18 GPa. This transition was observed at significantly lower pressures in DAC experiments. We obtained the isothermal bulk modulus of cubic phase K-0 = 252(28) GPa and its pressure derivative K' = 3.5(2.2). The thermal e xpansion coefficient of cubic phase at 25 GPa up to 1300 K was determined f rom interpolation of the P-V-T data obtained, and is 1.7(+/-0.7) x 10(-5) K -1 at 25 GPa.