Phase transitions in K_1−xRb_xSc(MoO₄)₂solid solutions

Abstract

K1− x Rb x Sc(MoO4)2 single crystals doped with Cr3+ were studied by electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy and optical microscopy. It has been found that the EPR spectra in solid solutions for x ≤ 0.2 are inhomogeneously broadened due to the random occupation of the next nearest-neighbour cation sites K+ and Rb+. The spin-Hamiltonian parameters describing the room-temperature EPR spectra of Cr3+ in K1− x Rb x Sc(MoO4)2 are calculated. The behaviour of the EPR spectra versus temperature reveals the existence of structural phase transitions in these crystals. The results show that a substitution of K+ by Rb+ suppresses the transition temperatures. The optical investigations carried out under the polarizing microscope have shown a ferroelastic nature of these transformations.