Optimized luminescent intensity of NaLa(MoO4)2: Ho3+,Yb3+ upconversion phosphors by orthogonal design and quadratic universal rotary methodology

To optimize the yellow upconversion luminescence intensity of NaLa(MoO₄)₂: Ho³⁺/Yb³⁺ phosphor material, we combined orthogonal experimental design and rotatable central composite design and adopted a two-step continuous optimization method to comprehensively optimize Ho³⁺ and Yb³⁺. Through this method, we determined the optimal ion doping concentrations for the strongest yellow light emission in this system. We synthesized the NaLa(MoO₄)₂: Ho³⁺/Yb³⁺ phosphor material with the strongest yellow upconversion luminescence intensity by the high-temperature solid-state reaction method and conducted a detailed study on the crystal structure and upconversion luminescence characteristics of the sample. Under 980 nm excitation, we measured the upconversion emission spectra of the optimal sample under different excitation currents. The results show that the yellow upconversion luminescence of the sample is a two-photon process, and the intensity limitation relationship is confirmed. Additionally, by applying the temperature sensitivity formula for non-thermally coupled energy levels, the relative sensitivity of Ho³⁺/Yb³⁺ doped phosphor was calculated to be 0.0062 K⁻¹. These findings demonstrate that NaLa(MoO₄)₂: Ho³⁺/Yb³⁺ possesses excellent upconversion luminescence properties, making it a strong candidate for yellow-emitting phosphors and a viable material for temperature sensing applications.