A study of substitutional disorder in Cr3+:CaYAlO4 .1. Fluorescence line narrowing

A high-resolution study of the optical properties of Cr3+-doped CaYAlO4 is presented. Excitation into the usual Cr3+ broad absorption bands produces fluorescence from a very broad R(1) line with a peak at 13 475 cm(-1) at 15 K. The R(2) line is observed at an energy 160 cm(-1) higher at temperatures above 100 K or by using excitation spectroscopy. The large broadening of the (2)E excited state is attributed to substitutional disorder at the Ca2+ and Y3+ sites on the basis of site selective excitation and fluorescence line narrowing measurements. Estimates of the distributions of octahedral and non-octahedral contributions to the crystal field are made and it is shown that the non-octahedral crystal field is dominant.