Synthesis and characterization of SrSnO3 doped with Er3+ for up-conversion luminescence temperature sensors

Abstract

The present work shows the results of the synthesis of SrSnO₃:Er³⁺ (doped from 0% to 7% with Er³⁺) prepared using a sol–gel method. Structural studies based on powder X-ray diffraction (XRD) showed that the compounds crystallize in an orthorhombic perovskite type structure (space group: Pbnm). The infrared spectra (IR) of Er₂O₃, SrSnO₃ and SrSnO₃:Er (1%) were measured in the range of 400–1000 cm⁻¹, which confirmed the octahedral tilting of SnO₆. The dependence of the green and red up-conversion (UC) emission bands on the pump power have been investigated using NIR (975 nm) laser irradiation. The decay curve was collected to determine the plausible mechanisms of the UC green emission, which showed that a Ground-State Absorption/Excited-State Absorption (GSA/ESA) process involving two photons was the indicated mechanism for this emission. The optical temperature sensing properties were investigated using the fluorescence intensity ratio technique (FIR) for the green UC emission. The temperature dependence of the green emissions at 528 nm (²H_11/2 → ⁴I_15/2) and 549 nm (⁴S_3/2 → ⁴I_15/2) were investigated. The maximum temperature sensitivity over the range of 294–372 K was 7.91 × 10⁻³ K⁻¹ at 368 K, and the sensor sensitivity was 9.97 × 10⁻³ K⁻¹ at 294 K. The results suggest that Er³⁺ doped SrSnO₃ is a promising material for optical temperature sensors for biological processes.