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

Although rare-earth (RE 3+ )-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 Mo 6+ ion stoichiometry on the crystal structure, NTE behavior, and photoluminescence (PL) thermal response characteristics in Er 3+ , Yb 3+ co-doped Sc 2 Mo 3(1+x) O 12 phosphors (−0.1 ≤ x ≤ 0.1). The results reveal that augmenting the Mo 6+ 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 Er 3+ and Yb 3+ ions. Consequently, the thermal enhancement factor for the upconversion luminescence of Er 3+ ions decreases with increasing Mo 6+ content, whereas the factor for near-infrared downshifting luminescence increases. Additionally, using the luminescence intensity ratio between the 1550 nm emission of Er 3+ and the 1050 nm emission of Yb 3+ for temperature sensing, a maximum relative sensitivity of 3.97 % K −1 is achieved in Sc 2 Mo 3.21 O 12 : Er 3+ , Yb 3+ . These findings provide insights into the synchronous regulation of the NTE and luminescence properties of RE 3+ -doped NTE phosphors for versatile applications.