Synthesis and luminescence properties of Eu3+ doped potassium titano telluroborate (KTTB) glasses for red laser applications

Abstract

A novel series of europium doped potassium titano telluroborate (Eu3+: KTTB) glasses were prepared with the melt quenching and characterized with XRD, SEM, FTIR, UV–Vis–NIR spectrometer, PL etc. And their bonding parameter (δ), the Judd-Ofelt (J-O) parameters, as well as the radiative parameters such as the stimulated emission cross-section, the lifetime and the quantum efficiency, were calculated, evaluated and analysed. The results show that their density, refractive index, and field strength increase with Eu3+ ion concentration. Both X-ray diffraction pattern and SEM image represent the amorphous nature of the glasses. The δ values of the samples are positive, and increases with Eu3+ ion concentration. The optical band gap decreases with increase of Eu3+ ion concentration, while the Urbach energy value keeps increase. The J-O parameters for all the samples follow the same trend as Ω2> Ω4> Ω6, and both Ω2 and Ω4 increase first then decrease with Eu3+ ion concentration, 2EuKTTB glass possesses the highest Ω2 (8.05 × 10–20cm2) value. The emission spectra exhibit five peaks in the visible region centering around 579, 591, 613, 652 and 700 nm, respectively, in which the red emission at 613 nm from 5D0→7F2 transition has the highest intensity increasing with Eu3+ ion concentration increase from 0.1 to 2 wt. % then decreasing at higher concentration. The colour coordinates dominate the reddish region of the CIE 1931 diagram, showing that the glasses are potentially suitable for red laser and colour display device applications. The asymmetric intensity ratio (AIR) and correlated colour temperature (CCT) has been also evaluated, both of which increase first and then decrease with Eu3+ ion concentration and almost get their maximum at the doped 2 wt. %. The decay time of 5D0 metastable state to the lower state exhibits single exponential nature. The lifetime decreases with Eu3+ ion concentration, while the quantum efficiency η (%) increases first but decreases after the doped 2 wt. %. 2EuKTTB glass is of the highest value of either the stimulated emission cross-section (7.55 × 10–22 cm2) or the quantum efficiency (90.1 %) among all the glasses.