Temperature sensitivity modulation through changing the vanadium concentration in a La2MgTiO6:V5+,Cr3+ double perovskite optical thermometer

Abstract

To fulfil the requirements of operating at low temperature in a harsh environment, the investigation on optical thermometers plays an increasingly important role. In this work, the influence of vanadium concentration on the capability of temperature readout by La₂MgTiO₆:V⁵⁺,Cr³⁺ luminescent thermometers was investigated for the first time. The presence of V³⁺ and V⁵⁺ was verified by XPS and absorption measurements. In the emission spectra, a blue–green emission region was assigned to both host and V⁵⁺ emission. Moreover, a spin-forbidden emission of Cr³⁺ ions was also detected. Vanadium ions in the +3 oxidation state do not exhibit luminescence, but play a role as a charge compensator. The highest emission intensity was obtained from the sample doped with 0.1% V. Besides, with increasing vanadium concentration, a redshift in the maximum position of the spectrum was observed corresponding to a movement from the greenish blue to yellowish green region in the CIE1931. It was shown that the relative sensitivity (S_r) and the temperature operating range can be easily modified by changing the concentration of vanadium ions. In particular, the outstanding relative sensitivities of 1.71% K⁻¹ (at 187 K) and 1.96% K⁻¹ (at 165 K) obtained from La₂MgTiO₆:0.1%V⁵⁺,Cr³⁺ and La₂MgTiO₆:0.05%V⁵⁺,Cr³⁺ demonstrated the enormous potential of this material for thermal sensing application.