Optical pressure and temperature sensing properties of Nd³⁺:YTaO₄

The pressure- and temperature-dependent luminescence properties of M'-phase Nd³⁺:YTaO₄ synthesized by a molten salt method are presented. Ten near-infrared emission lines originating from the transitions between the two Stark levels R_1,2 of the ³F_3/2 state and the five Stark levels Z_1,2,3,4,5 of the ⁴I_9/2 state for the doped Nd³⁺ ions can be clearly identified. All these emission lines are found to shift linearly with pressure in a range up to ∼11 GPa. The R_2,1 → Z₅ emission lines have larger pressure sensitivities, which are 16.44 and 14.27 cm^-1 GPa^-1. The intensities of all the emission lines evolve with pressure non-monotonically, and peak at ∼1 GPa. The R₁ → Z_4,5 and R₂ → Z₁ emission lines can be obviously narrowed under the hydrostatic pressure, and broadened under the non-hydrostatic pressure, indicating their potential capability for reflecting the characteristic of a pressure environment. The intensity ratio of the R_2,1 → Z₅ emission lines exhibits a large temperature dependence, with a relative sensitivity between 0.129% and 0.108% K^-1 in the physiological temperature range of 290-320 K. Thermal variations of the spectral positions and widths of the R_2,1 → Z₅ emission lines are also investigated. A high thermal stability for the position of the R₂ → Z₅ emission line is revealed. Based on the experimental results, the advantages and potential of Nd³⁺:YTaO₄ as a multi-functional sensor for pressure and temperature are discussed.