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

Highlights: • A novel series of Eu³⁺: KTTB glasses were synthesized with melt quenching. • The emission spectrum has 5 visible peaks, of which 613-nm red one is the strongest. • The colour coordinates dominate the reddish region of the CIE 1931 diagram. • The glass quantum efficiency increases first then decreases with Eu³⁺ concentration. • 2EuKTTB glass is of the highest value of the quantum efficiency, 90.1 %. 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.