For the development of optical temperature sensor, a series of GdTaO₄ phosphors with various Er³⁺‐doping concentrations (0, 1, 5, 10, 25, 35, 50 mol%) were synthesized by a solid‐state reaction method. The monoclinic crystalline structure of the prepared samples was determined by X‐ray diffraction (XRD). Under excitations of 980 and 1550 nm lasers, the multi‐photon‐excited green and red upconversion (UC) luminescence emissions of Er³⁺ were studied, and the critical quenching concentration of Er³⁺‐doped GdTaO₄ phosphor was derived to be 25 mol%. By changing the pump power of laser, it was found that the two‐photon and three‐photon population processes happened for the UC emissions of Er³⁺‐doped GdTaO₄ phosphors excited by 980 and 1550 nm lasers, respectively. Furthermore, based on the change of thermo‐responsive green UC luminescence intensity corresponding to the ²H_11/2 → ⁴I_15/2 and ⁴S_3/2 → ⁴I_15/2 transitions of Er³⁺ with temperature, the optical temperature sensing properties of Er³⁺‐doped GdTaO₄ phosphor were investigated under excitations of 980 and 1550 nm lasers by using the fluorescence intensity ratio (FIR) technique. It was obtained that the maximum absolute sensitivity (S_A) and relative sensitivity (S_R) of Er³⁺‐doped GdTaO₄ phosphors are as high as 0.0041 K⁻¹ at 475 K and 0.0112 K⁻¹ at 293 K, respectively. These significant results suggest that the Er³⁺‐doped GdTaO₄ phosphors are a promising candidate for optical temperature sensor.

中文翻译：

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基于Er3 +掺杂的GdTaO4荧光粉上转换发光的光学温度传感器

为了开发光学温度传感器，通过固态反应方法合成了一系列具有不同Er ³⁺掺杂浓度（0、1、5、10、25、35、50 mol％）的GdTaO ₄荧光粉。通过X射线衍射（XRD）确定所制备样品的单斜晶体结构。在980和1550 nm激光的激发下，研究了Er ³⁺的多光子激发绿色和红色上转换（UC）发光发射，得出掺Er ^3+的GdTaO ₄荧光粉的临界猝灭浓度为25摩尔％。通过改变激光的泵浦功率，发现Er ³⁺的UC发射发生了两光子和三光子的填充过程分别由980和1550 nm激光激发的掺GdTaO ₄荧光粉。此外，根据对应于Er ³⁺的² H _11/ ²  →  ⁴ I _15/2和⁴ S _3/2  →  ⁴ I _15/2跃迁的热响应绿色UC发光强度 随温度的变化，光学使用荧光强度比（FIR）技术在980和1550 nm激光激发下研究了掺Er ^3+的GdTaO ₄荧光粉的温度感测特性。得出最大绝对灵敏度（S _A）和掺Er ^3+的GdTaO ₄荧光粉的相对灵敏度（S _R）分别在475 K和293 K下分别高达0.0041 K ^-1和0.0112 K ^-1。这些重要结果表明，掺Er ^3+的GdTaO ₄荧光粉是光学温度传感器的有希望的候选物。