Enhanced up-conversion luminescence and optical thermometry characteristics of Er³⁺/Yb³⁺ co-doped transparent phosphate glass-ceramics

Novel Er³⁺/Yb³⁺ co-doped transparent glass-ceramics (GCs) containing orthorhombic NaZnPO₄ nanocrystals (NCs) were successfully prepared for the first time by a conventional melt-quenching and subsequent heating. Under 980 nm laser prompting, the GC samples produced intense red and green up-conversion emissions. The emission intensities varied with Yb³⁺ concentration and heat treatment conditions. Optimum emission intensities were obtained for the sample with 2 mol% of Yb³⁺ heat treated at 580 °C for 4 h. Furthermore, the temperature dependent fluorescence intensity ratio (FIR) of thermally coupled emitting states (⁴S_3/2, ²H_11/2) in Er³⁺/Yb³⁺ co-doped GCs was evaluated under 980 nm. A high relative temperature sensitivity of 1.329% K⁻¹ was obtained at 303 K and the maximal absolute temperature sensitivity at 612 K was evaluated to be 5.732 × 10⁻³ K⁻¹. It is expected that the as-fabricated GCs containing NaZnPO₄ NCs are an efficient up-conversion material with potential application in optical temperature sensor.