Ca3TeO6:Er3+: A green phosphor for bifunctional applications in non-contact optical thermometry and w-LEDs

Abstract

The green Ca₃TeO₆:Er³⁺ phosphors were prepared by means of solid-state reaction at a high temperature. The crystalline phase, elemental mapping, photoluminescence (PL) spectra, and Commission International de L’Eclairage (CIE) chromaticity coordinates of the synthesized compounds were employed to characterize the materials comprehensively. The bandgap energy (E_g) of Ca₃TeO₆ was calculated to be 3.007 eV using Density Functional Theory (DFT). Analysis of the diffuse reflection spectra (DRS) further demonstrated its suitability as a phosphor host matrix. The Ca₃TeO₆:Er³⁺ phosphor exhibited strong excitation under 378 nm irradiation, displaying three characteristic emission peaks. The dominant emission peaks were observed at 523 nm and 545 nm, which align with the characteristic electronic transitions of Er³⁺ ions at ²H_11/2-⁴I_15/2 and ⁴S_3/2-⁴I_15/2, respectively. A regular concentration quenching behavior was observed, with the optimum Er³⁺ doping concentration determined to be 5.0 mol%. The prepared phosphors demonstrated significant temperature sensitivity over the range of 300-480 K when utilizing the fluorescence intensity ratio (FIR) technology. A maximum relative sensor sensitivity was 1.18% K⁻¹ at 300 K indicating excellent potential for non-contact thermometry applications. Furthermore, the prepared white light-emitting diode (w-LED) exhibited outstanding performance, characterized by a high color rendering index (R_a) of 92. Overall, these results indicate that Ca₃TeO₆:Er³⁺ phosphors hold significant potential for use in solid-state lighting as well as in non-contact temperature sensing.