The vaterite-type ABO₃rare-earth borates

Abstract

Approximate models are proposed for the room temperature and the high temperature modifications of the vaterite-type rare earth borates. A low temperature model based on three-membered rings of borate tetrahedra is found to be reconcilable with the X-ray powder diffraction data, the optical properties, and the infrared absorption character. A high-temperature model containing triangular borate ions is relatable to the CaCO3 vaterite modification.