Elaboration, structural and spectroscopic properties of rare earth-doped yttrium–hafnium sol–gel oxide powders for scintillation applications

Hafnium dioxide (HfO2) presents a high crystalline density (≈10 g/cm3) which makes it attractive for host lattice activated by rare earths (RE) for applications as scintillating materials. The potentiality to prepare Eu3+ and Tb3+ activated HfO2 sol–gel powders, with high scintillation yield, is explored. The powders are heat-treated at 1000 °C before analyses. The incorporation of yttrium (Y3+) in various concentrations is conducted to vary the lattice phase and to stabilize the trivalent terbium ions. The influence of Y3+ on the microstructure and then on the scintillation properties of the material is presented. A high concentration of Y3+ (20 mol%) stabilizes pure HfO2 tetragonal phase whatever RE (1 mol%) doping. The powders with the highest relative scintillation yield are Eu3+:HfO2 without Y3+ incorporation and crystallized into the monoclinic phase and Y3+ (20 mol%): Tb3+:HfO2 crystallized into the tetragonal phase. Sequential energy transfer process is assumed to explain these results.