The high-pressure and temperature equation of state of a majorite solid solution in the system of Mg₄Si₄O₁₂-Mg₃Al₂Si₃O₁₂

The high-pressure and temperature equation of state of majorite solid solution, Mj_0.8Py_0.2, was determined up to 23 GPa and 773 K with energy-dispersive synchrotron X-ray diffraction at high pressure and high temperature using the single- and double-stage configurations of the multianvil apparatuses, MAX80 and 90. The X-ray diffraction data of the majorite sample were analyzed using the WPPD (whole-powder-pattern decomposition) method to obtain the lattice parameters. A least-squares fitting using the third-order Birch-Murnaghan equation of state yields the isothermal bulk modulus, K(TO) = 156 GPa, its pressure derivative, K' = 4.4(±0.3), and temperature derivative (partial differential K(T)/ partial differential T)(P) = -1.9(±0.3) x 10^-2 GPa/K, assuming that the thermal expansion coefficient is similar to that of pyrope-almandine solid solution.