On thermoluminescence of Lu2O3:Tb,Ta ceramic storage phosphors

For the first time thermoluminescence of Lu2O3:Tb,Ta ceramics sintered at 1700 °C in different atmospheres - air, forming gas and vacuum - were investigated. Exposure of the materials into the 254 nm radiation of a mercury lamp led to the Tb3+ green persistent luminescence of noticeable intensity. Thermoluminescence glow curves revealed two strong thermoluminescence peaks located around 170 °C and 250 °C, with the former being by a factor of ~2-2.5 more intense compared to the latter. Tmax-Tstop thermoluminescence experiments revealed that each of these bands is composed of numerous individual, strongly overlapping components of similar characteristics, known as continuous traps distribution. The highest thermoluminescence was observed from the material sintered in vacuum. Those sintered in air or forming gas showed the storage capabilities by about 15-25% lower, though shapes of their glow curves were very similar. A scheme of carriers trapping was proposed with the hole immobilized at Tb3+ site and the electron being trapped in the vicinity Ta(V) impurity due to its strong positive net charge in the Lu site.