Bi3+ sensitized Gd2O3:Eu3+: A potential red phosphor for UV LED pumped white light emission

Abstract

Bi3+ sensitized Gd2O3:Eu3+ phosphors were synthesized by hydrothermal method using polyvinylpyrrolidone as capping agent. As-prepared samples exhibit crystalline hexagonal phase Gd(OH)3. While post annealing at 900 °C, Gd(OH)3 transforms to cubic phase Gd2O3. The lattice substitution by Bi3+ in different symmetry sites, viz. C2 and S2 of Gd2O3 leads to 2 (two) prominent excitation bands related to the 1S0 → 3P1 of Bi3+. Both the excitation bands induce efficient energy transfer to the excited states of Eu3+. In both the cases, the energy transfer efficiency can reach upto ~97%. The energy transfer from the sensitizer (Bi3+) to the activator (Eu3+) occurs mainly through dipole-dipole interactions. The occurrence of energy transfer from Bi3+ to the Eu3+ is corroborated from both the steady state and decay lifetime studies. Color saturation of the red emission when excited in the wavelength range ~330–380 nm is observed ~70–85%. CIE chromaticity reveals the tunability of the color emission by changing the activator concentration.