White light tuning and temperature sensing of NaLu(WO4)2:Ln3+ up-converting phosphor

Abstract

NaLu(WO₄)₂:Ln³⁺ phosphors were synthesized via a hydrothermal method combined with subsequent calcination. Under excitation at 980 nm, 25%Yb³⁺, 0.5%Tm³⁺ and 25%Yb³⁺, 1%Ho³⁺-doped phosphors produce blue, green and red emissions. Namely, NaLu(WO₄)₂:25%Yb³⁺, 0.1%Ho³⁺, 0.1%Tm³⁺ nanocrystals show suitable intensities of blue, green, and red (RGB) emission, resulting in the production of perfect and bright white light with CIE-x = 0.3299 and CIE-y = 0.3293, which is very close to the standard equal energy white light illumination (x = 0.33, y = 0.33). Based on FIR theory, the temperature dependence of NaLu(WO₄)₂:20%Yb³⁺, 1%Er³⁺ was studied, and the maximum value of sensitivity was obtained as 1.38% K⁻¹ at 543 K, which is better than that of previously reported temperature-sensing materials. It proves that the NaLu(WO₄)₂:Ln³⁺ phosphors have potential applications in white lighting, optical temperature measurement and other fields.