LUMINESCENCE CHARACTERISTICS OF CASO4:TB,M (M=NA,K,RB) PHOSPHORS

Abstract

In the present study, the investigation of complex luminescence terbium centres as well as the analysis of technological features of the synthesis of small-grained wide-gap CaSO :Tb3+ anhydrite phosphors containing 1% of Tb3+ and some amount of additional impurity ions (Na+, K+, Rb+) have been continued using the methods of optical and thermoactivation spectroscopy. Of particular interest was a contribution of calcium ions into formation of complex luminescence centres. Ca causes efficient dynamic hybridization of electronic states and influence on the formation of terbium and near-terbium electronic excitations. The excitation spectra of Tb3+-centre emission have been measured in the VUV spectral range at 77 or 300 K. The excitation band related to the lowest f–d transition of Tb3+ ions at ≈5.9 eV in CaSO4 undergoes broadening toward the long- wavelength side, when the radius of a charge compensator increases (K+→ Rb+). The band at 7.5–9 eV ascribed to the excitation of oxyanions has a different shape in CaSO4:Tb,K and CaSO4:Tb,Rb. Thermally stimulated luminescence (80–700 K) have been analyzed for a set of anhydrite phosphors previously irradiated by X-rays at 80 and 300 K. Keywords: CaSO , Tb3+, photoluminescence, thermoluminescence, vacuum ultraviolet spectroscopy.