Judd-Ofelt and chromaticity analysis of hafnia doped with trivalent europium as a potential white LED phosphor

Abstract

Judd-Ofelt analysis of HfO2:Eu3+ with various europium doping concentrations, formed by plasma electrolytic oxidation, had been investigated. Ω2 parameter is increasing, while Ω4 parameter shows no concentration dependence. For the highest europium doping concentration of 0.62 at% Ω2 = 4.03·10−20 cm2 and Ω4 = 2.26·10−20 cm2. Radiative transition probabilities of each allowed emitting level were calculated. The radiative lifetime of 5D0 emitting level and a relatively high cross section of emission 5D0→7F2 were estimated: 1.58 ms and 13.49·10−22 cm2, respectively. CIELUV coordinates of photoluminescence of HfO2 doped with various europium concentrations and by excitation with UV 270 nm and 395 nm beam had been calculated and plotted to the CIE 1976 diagram. For low concentrations HfO2:Eu3+ and UV excitation the material gives almost pure white luminescence, which is an indication for its potential use as a white LED phosphor.