Synthesis and luminescent properties of near-UV excited NaLa(MoO4)2:Er3+ phosphors for multifunctional applications

Abstract

Luminescent and temperature sensing properties of single Er3+ ions doped NaLa(MoO4)2 phosphors were prepared by a high-temperature solid-state reaction technique. Under 380 nm of light illumination, all the prepared compounds exhibited the characteristic emission properties of Er3+ ions and the optimum doping concentration was 0.02 mol while the color coordinate was found to be (0.253, 0.721). The mechanism of concentration quenching was dominated by the electric dipole-dipole interaction which was confirmed by Dexter theory owing to the overstepped critical distance value of 25.14 Å. The fabricated white light-emitting diode device exhibited color rendering index and correlated color temperature values of 79.86 and 5236 K based on 385 nm near-ultraviolet chip. Additionally, the thermal stability of the NaLa(MoO4)2:0.02Er3+ phosphor was studied and the activation energy was estimated to be 0.28 eV. The optical temperature sensing sensitivity of the obtained sample was also investigated by the fluorescence intensity ratio technique to analyze the two thermally-coupled levels (2H11/2, 4S3/2) and the maximum sensor sensitivity was demonstrated to be about 0.0138 K−1 at 483 K. Eventually, the soft polydimethylsiloxane film with optimum doping concentration was fabricated and emitted a green-emitting glow.