Luminescence and dielectric properties of nano-structured Eu<SUP>3+</SUP>: K<SUB>2</SUB>O-Nb<SUB>2</SUB>O<SUB>5</SUB>-SiO<SUB>2</SUB> glass-ceramics

In the present study, results concerning luminescence and dielectric properties of Eu<SUB>2</SUB>O<SUB>3</SUB> (0.5 wt% in excess) doped nano-crystallized KNbO<SUB>3 </SUB>containing transparent glass-ceramics obtained from glass of composition 25K<SUB>2</SUB>O-25Nb<SUB>2</SUB>O<SUB>5</SUB>-50SiO<SUB>2</SUB> (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 KNbO<SUB>3</SUB> in glass matrix. The absorption spectra of all the samples have revealed the characteristic 4f-4f intraband absorption transitions of Eu<SUP>3+</SUP> ions. The measured photoluminescence spectra have exhibited emission transitions<SUP> 5</SUP>D<SUB>0, 1</SUB> → <SUP>7</SUP>F<SUB>j</SUB> (j = 0, 1, 2, 3 and 4) of Eu<SUP>3+</SUP> ions. The excited level lifetimes have been determined from measured fluorescence decay curves. The rare earth ion site symmetry (nearly C<SUB>v</SUB>) has been understood based on the nature of the Stark splittings of emission bands detected in both Eu<SUP>3+</SUP>: glass and Eu<SUP>3+</SUP>: glass-ceramics