The luminescence of VO43− ions in Ca2PO4Cl

Abstract

The emission spectra of both single crystals and polycrystalline samples of Ca₂PO₄Cl “doped” with VO₄³⁻ have been measured at several temperatures from 10 K to room temperature. In both a wide emission band has been observed within the range 16000–28000 cm⁻¹. This band shows two components, which behave differently with temperature. The deconvolution of the decay curves, expressed in terms of a linear combination of exponentials, requires three exponentials below 250 K. The relative lifetimes are 3700 μs, 1800 μs and 250 μs at 10 K. The emission wide band is assigned to a triplet → singlet transition connected to a transfer of an electron from a molecular orbital mainly localized on one oxygen atom (2pπ type) to a molecular orbital mainly localized on the vanadium atom (d_e, or d_i2 type). The lifetimes of the single crystal and of the polycrystalline samples are rather close. However there is evidence of a somewhat different behaviour of the two kinds of samples with temperature.