Modulation of negative thermal expansion and luminescence anti-thermal quenching properties of Er3+-Yb3+ co-doped Sc2Mo3(1+x)O12 via host matrix engineering

Abstract

Although rare-earth (RE³⁺)-doped negative thermal expansion (NTE) luminescent materials exhibit promising anti-thermal quenching effects, limited progress has been made in modifying their NTE and luminescence performances. This study investigates the impacts of Mo⁶⁺ ion stoichiometry on the crystal structure, NTE behavior, and photoluminescence (PL) thermal response characteristics in Er³⁺, Yb³⁺ co-doped Sc₂Mo_3(1+x)O₁₂ phosphors (−0.1 ≤ x ≤ 0.1). The results reveal that augmenting the Mo⁶⁺ content results in a transition from three-dimensional to two-dimensional NTE behavior in the host material due to the change in steric hindrance. This transition modulates cross-relaxation and back energy transfer processes between the doped Er³⁺ and Yb³⁺ ions. Consequently, the thermal enhancement factor for the upconversion luminescence of Er³⁺ ions decreases with increasing Mo⁶⁺ content, whereas the factor for near-infrared downshifting luminescence increases. Additionally, using the luminescence intensity ratio between the 1550 nm emission of Er³⁺ and the 1050 nm emission of Yb³⁺ for temperature sensing, a maximum relative sensitivity of 3.97 % K⁻¹ is achieved in Sc₂Mo_3.21O₁₂: Er³⁺, Yb³⁺. These findings provide insights into the synchronous regulation of the NTE and luminescence properties of RE³⁺-doped NTE phosphors for versatile applications.