Effect of charge compensators (Na+, Mg2+, Bi3+) on the photoluminescence properties of ZnAl2O4:Sm3+orange-red light emitting nanophosphor

Abstract

This research work presents the synthesis of ZnAl₂O_4, samarium doped ZnAl₂O₄: x%Sm³⁺ (x = 1–11mol%) and co-doped ZnAl₂O₄: x%Sm³⁺, Aⁿ⁺ (x = 5mol%, Aⁿ⁺ = Na⁺, Mg²⁺, Bi³⁺) nano phosphors. All prepared samples are calcinated at an optimized temperature of 900^⁰C. Powder XRD studies reveal that all synthesized samples are crystallized in cubic phase, with Fd-3 m space group, matches with JCPDS # 05–0669. The ZnAl₂O₄: Sm³⁺ exhibits major excitation peaks at 274, 306, 346, 377, 404, 418, 442 and 466 nm. Inquiringly, we perform photoluminescence studies under the excitation of 274 nm and 404 nm. With 404 nm excitation, the emission peak intensity of ZnAl₂O₄: x% Sm³⁺ (x = 1–11 mol%) achieves its maximum when the doping concentration is 5 mol%. Charge compensators effect of different valance cation co-dopants (Aⁿ⁺ = Na⁺, Mg²⁺, Bi³⁺) on the PL emission intensity is further optimized at the concentration of 2 mol% for 274 nm excitation. CIE1931 color coordinates for ZnAl₂O₄:5mol% Sm³⁺:2mol%Mg²⁺ phosphor, (0.656, 0.343), closely approximate those of an ideal orange-red light emitting phosphor (0.670, 0.333). Measurements reveal that the average decay time for ZnAl₂O₄:5mol% Sm³⁺ and ZnAl₂O₄:5mol% Sm³⁺: Mg²⁺2mol% is 0.98 ms and 0.057 ms, respectively. This paper also summarizes the typical behavior of ZnAl₂O₄ and its Cr³⁺ association when excited by 404 nm light, for researchers interested in zinc aluminates.