Thermoluminescent characterization of HfO₂: Tb³⁺ synthesized by hydrothermal route

Thermo and photoluminescent properties of nanoparticles (NPs) of hafnium oxide (HfO₂), both intrinsic and doped with terbium (Tb³⁺) are reported. The NPs of HfO₂ were synthesized by hydrothermal route, using hafnium tetrachloride (HfCl₄) and terbium chloride hexahydrated (TbCl₃{bullet operator}6H₂O) as precursors and sodium hydroxide (NaOH) to adjust the pH. Deionized water was used as solvent in all cases. The synthesis was carried out at different dopant concentrations from 0 to 20at% of terbium with respect to the amount of hafnium in the precursor solution. The temperature of hydrothermal treatment was 200°C and 80min of reaction time. X-ray diffraction results show that at terbium concentrations higher than 15at% the HfO₂ nanoparticles have a crystalline structure corresponding to the tetragonal phase. Thermoluminescent (TL) characterization was performed after 5min irradiation of the samples with ultraviolet light of 200nm wavelength. The highest TL emission was observed on samples with 7at% of Tb, with the TL peak centered at 128°C. Thermoluminescence analysis shows behavior associated with second-order kinetics with activation energy of 0.49eV. Photoluminescent spectrum present the characteristics ⁵D₄→⁷FJ (J=3-6) terbium ion electronic transitions lines centered on 489nm, 543nm, 584nm and 622nm.