Highly sensitive optical temperature sensing based on upconversion luminescence in Gd9.33(SiO4)6O2:Yb3+–Er3+/Ho3+ phosphors

Abstract

In this paper, new upconversion (UC) phosphors for Yb³⁺–Er³⁺- and Yb³⁺–Ho³⁺-doped Gd_9.33(SiO₄)₆O₂ (GSO) were designed via a solid-state reaction method. The phase purity of the samples was examined using XRD patterns. In Yb³⁺–Er³⁺ -doped GSO, the characteristic emission peaks of Er³⁺ appear upon 980 nm excitation, and the optimum Er³⁺ concentration was found to be 1 mol%. Different changes in the intensity of green and red emissions with Er³⁺ concentration appeared, and were interpreted by cross-relaxation between Er³⁺ ions. In Yb³⁺–Ho³⁺-doped GSO, three emission peaks of Ho³⁺ were observed, and the power-dependent UC luminescence was studied. For studying the temperature-sensing properties, different strategies were employed, including thermally coupled levels and non-thermally coupled levels. High sensitivities were obtained in the phosphors, and GSO:Yb³⁺,Er³⁺ showed the highest sensitivities. The above investigation results indicated that the developed GSO:Yb³⁺–Er³⁺/Ho³⁺ phosphors could have potential applications in optical thermometry.