Yb3+, Er3+, Tm3+ co-doped β'Gd2(MoO4)3 for high sensitivity luminescence thermometry spanning from 300 to 890 K

Temperature sensing by using near-infrared (lambda = 976 nm)-excited upconversion (UC) of Yb, Er and Tm co-doped orthorhombic beta'Gd-2(MoO4)(3) combines remarkable good sensitivity and thermal resolution from room temperature to 890 K, thanks to the use of three different ratiometric luminescence probes. Two of them are based on pairs of thermally coupled levels, namely H-2(11/2)-> I-4(15/2) vs S-4(3/2)-> I-4(15/2) Er3+ green emissions (R1) and deep-red F-3(3)-> H-3(6) vs NIR H-3(4)-> H-3(6) Tm3+ emissions (R3). The third one uses non-thermally coupled levels, blue (1)G(4)-> H-3(6) vs deep-red F-3(3)-> H-3(6) Tm3+ emissions (R2). This multiprobe approach allows the optimization of the thermometric parameters for each selected temperature range. Based on absolute thermal sensitivity (S-ABS), R1 is the best option for sensing from room temperature up to about 442 K, with R1 S-ABS = 10(3) x 10(-4) K-1 and excellent thermal resolution delta T < 0.04 K at 300 K, while at higher temperatures, R2 is the most adequate probe since it combines an extraordinary increase of R2 S-ABS up to 20300 x 10(-4) K-1 at 776 K and very good delta T < 0.2 K. When the relative thermal sensitivity (S-REL) evaluation is required, R-3 is the probe of choice from room temperature up to 522 K, offering simultaneously the highest R3 S-REL = 3.3% K-1 and delta T = 0.07 K at 300 K, with a minimum delta T = 0.05 K achieved at 522 K, but R2 is still the most convenient probe for high temperature sensing, with R2 S-REL = 1.6% K-1 and delta T = 0.25 K. Therefore, doping beta'Gd2(MoO4)(3) simultaneously with Er3+ and Tm3+ provides a unique way to span the sensing temperature up to 890 K while maintaining suitable high thermal sensitivity and thermal resolution along the whole temperature range. Several favourable UC aspects specific of beta'Gd-2(MoO4)(3) are identified as being responsible for advantages over its beta NaYF4 counterpart for high temperature sensing. (C) 2022 The Author(s). Published by Elsevier B.V.