Absorption spectra of zircon crystals doped with Cr(IV): ZrSiO 4:Cr 4+

Abstract

Crystals of ZrSiO 4 ‘doped’ with Cr 4+ have been prepared from oxide fluxes. The polarized absorption spectra (α,σ,π) of single crystals have been recorded in the range 6000–25 000 cm −1 at various temperatures from 10 K to room temperature. The polarized absorption spectra present three main wide bands in the regions 9600–14 000 (π), 15 000–19 500 (α, σ) and 20 500–24 000 (α, σ) cm −1. It is shown that with these spectra only the hypothesis of a replacement of Si 4+ with Cr 4+ is acceptable. An explanation and assignment of the bands are proposed by considering their polarizations and the site symmetry perturbation related to the distortion T d → D 2 d of the oxygen coordination. In particular the first band is assigned to the transition 3 A 2( 3 T 1, et 2)← 3 B 1 and the next two bands to the transitions 3 E( 3 T 1, et 2)← 3 B 1 and 3 E( 3 T 1, t 2)← 3 B 1 . This result agrees with a recent investigation on Y 3Al 5O 12:Cr 4+.