Structure, dielectric and optical properties of transparent Nd3+: KNbO3 nanocrystalline glass–ceramics

Here, glass in the composition of 25K2O–25Nb2O5–50SiO2 (mol%) doped with Nd2O3 (0.5 wt.% in excess) was isothermally crystallized at 800 °C for 1–100 h. Their structures, dielectric and optical properties were analyzed with the progress of nanocrystallization of Nd3+: KNbO3 by XRD, FESEM, TEM, FTIRRS, DC, optical absorption and fluorescence measurements. Crystallization of KNbO3 is confirmed from XRD and the appearance of 749 cm−1 band in the FTIRRS spectra. The crystallite size estimated from XRD and TEM is found to vary in the range 7–11 nm. The formation of ferroelectric nano-crystalline KNbO3 phase is also attributed by a steep rise in the dielectric constant (ε) of glass–ceramics with heat-treatment time. The measured photoluminescence spectra have exhibited emission transitions of 4F3/2 → 4IJ (J = 9/2, 11/2 and 13/2) from Nd3+ ions upon excitation at 817 nm. It is observed that the photoluminescent intensity and excited state lifetime of Nd3+ ions initially decrease and then gradually increase with increase in heat-treatment time. The absorption spectra and fluorescence measurements disclose that the Nd3+ ions gradually enter into the KNbO3 nanocrystals.