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 pressures of 4-29 GPa and temperatures of 300-1400 K using sintered diamond anvils in a 6-8 type high-pressure apparatus. Orthorhombic phase (α-PbO₂ structure) underwent a transition to a cubic phase (Pα3̄ structure) at 18 GPa. This transition was observed at significantly lower pressures in DAC experiments. We obtained the isothermal bulk modulus of cubic phase K₀ = 252(28) GPa and its pressure derivative K′ = 3.5(2.2). The thermal expansion coefficient of cubic phase at 25 GPa up to 1300 K was determined from interpolation of the P-V-T data obtained, and is 1.7(± 0.7) × 10^-5 K^-1 at 25 GPa.