Synthesis and High-Pressure Study of Corundum-Type In2O3

This work reports the high-pressure and high-temperature (HP-HT) synthesis of pure rhombohedral (corundum-type) phase of indium oxide (In2O3) from its most stable polymorph, cubic bixb-yite-type In2O3, using a multianvil press. Structural and vibrational properties of corundum-type In2O3 (rh-In2O3) have been characterized by means of angle-dispersive powder X-ray diffraction and Raman scattering measurements at high pressures which have been compared to structural and lattice dynamics ab initio calculations. The equation of state and the pressure dependence of the Raman-active modes of the corundum-type phase are reported and compared to those of corundum (alpha-Al2O3). It can be concluded that rh-In2O3 is stable under compression up to 14 GPa and it gradually transforms to the orthorhombic Rh2O3-III structure with Pbca space group (N. 61) between 14 and 26 GPa. The bulk modulus, axial compressibilities, and the pressure range of stability of the corundum-type phase in group IIIA sesquioxides A(2)O(3) (A = Al, Ga, and In) are discussed.