Influence of temperature on near-infrared luminescence, energy transfer mechanism and the temperature sensing ability of La2MgTiO6: Nd3+ double perovskites

La2MgTiO6: Nd3+ samples synthesized by the coprecipitation method crystallized in an orthorhombic phase with space-group Pbnm (62). The SEM images of the sample showed heterogeneous morphology and the average crystallite size was 0.7 mu m. Luminescent spectra, typical for Nd3+ ions at low symmetry site (C-s), were observed in all samples excited at 266 nm and 808 nm. The highest emission intensity was obtained for the sample doped with 3% Nd3+. The emission lifetimes at 77 K and 300 K shorten with increasing Nd3+ concentration due to cross-relaxation processes. Noticeably, the lengthening of the decay times at 300 K, as compared to 77 K, resulted from the thermalization of the higher Stark component of the F-4(3/2) level. In addition, the experimental data were analysed using the Inokuti - Hirayama model; the energy transfer between Nd3+ ions was predominantly regulated by the dipole-dipole interaction. The critical transfer distance R-0, critical concentration C-0, energy transfer parameter C-da, and energy transfer probability W-da were found to be 4.9 angstrom, 2 x 10(21) ions cm(3), 5.67 x 10(-4)1 cm(6).S-1, and 4004 s(-1), respectively. Furthermore, the temperature-dependent luminescence exhibited good thermal stability with temperature quenching at 450 K. The temperature sensing ability of the sample doped with 5 % Nd3+, based on the emission of two thermally coupled F-4(5/2) and F-4(3/2) levels, was investigated. The highest value of the relative sensitivity was 0.81 and 0.83 % K-1 at 248 K and 275 K, respectively. (C) 2020 Elsevier B.V. All rights reserved.