Luminescence and dielectric properties of nano-structured Eu³⁺: K₂O-Nb₂O₅-SiO₂ glass-ceramics

Abstract

In the present study, results concerning luminescence and dielectric properties of Eu₂O₃ (0.5 wt% in excess) doped nano-crystallized KNbO₃ containing transparent glass-ceramics obtained from glass of composition 25K₂O-25Nb₂O₅-50SiO₂ (mol%) by varied heat-treatment duration at 800 °C have been analyzed and reported. The formed crystallization phase, crystallite size and morphology have been examined through XRD, FESEM, TEM and FTIRRS measurements. The observed steep increase in the dielectric constant (ε ) of glass-ceramics over the as-prepared glass is attributed to the formation of ferroelectric nano-crystalline KNbO₃ in glass matrix. The absorption spectra of all the samples have revealed the characteristic 4f-4f intraband absorption transitions of Eu³⁺ ions. The measured photoluminescence spectra have exhibited emission transitions ⁵D_{0, 1} → ⁷F_j (j = 0, 1, 2, 3 and 4) of Eu³⁺ ions. The excited level lifetimes have been determined from measured fluorescence decay curves. The rare earth ion site symmetry (nearly C_v) has been understood based on the nature of the Stark splittings of emission bands detected in both Eu³⁺: glass and Eu³⁺: glass-ceramics.