Temperature dependent upconversion luminescence of GdScO₃ phosphors with low phonon energy for optical thermometry

Non-contact optical temperature sensing technology, particularly based on the fluorescence intensity ratio principle of the thermally coupled energy levels of Er³⁺, has emerged as a prominent area of research for upconversion luminescent materials in temperature detection. To advance the development of novel upconversion luminescent materials for optical temperature sensing, an upconversion phosphor, GdScO₃:Yb³⁺/Er³⁺, with low phonon energy, was synthesized using a high-temperature solid-state method. The crystal structure, maximum phonon energy, and elemental distribution of the sample were characterized through powder X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and Fourier transform infrared spectroscopy. The upconversion emission spectrum of the sample under 980 nm excitation and the excited state absorption process under different power density excitations were thoroughly investigated. The findings demonstrate the commendable performance of the GdScO₃:Yb³⁺/Er³⁺ phosphor, which exhibits a suitable thermally coupled energy levels energy difference (ΔE) of 630 cm^− 1, an exceptional relative sensitivity of 1.007% K^− 1 at 300 K, and a minimal temperature resolution of 0.49 K at 300 K. The remarkable consistency and robust thermal stability of the GdScO₃:Yb³⁺/Er³⁺ phosphors underscore their potential in highly sensitive optical thermometry applications.