Cr3+-Doped InTaO4 phosphor for multi-mode temperature sensing with high sensitivity in a physiological temperature range

Abstract

With the increasing demand for non-contact temperature sensing, the development of an optical thermometer with excellent performance is more and more compelling. A Cr³⁺-doped InTaO₄ phosphor was prepared for the implementation of multi-mode high-sensitivity optical temperature sensing. Its temperature-dependent fluorescence intensity and fluorescence lifetime in the temperature range from 240 to 420 K were investigated in detail for achieving two different temperature sensing modes. At 347 K, the optimal relative temperature sensitivities are 2.50% K⁻¹ for the fluorescence intensity mode and 2.27% K⁻¹ for the fluorescence lifetime mode, respectively. Moreover, due to the rapid decrease of the fluorescence lifetime of Cr³⁺, another temperature sensing scheme based on a time-resolved technique was also presented. Here, the fluorescence intensities of Cr³⁺ in two different time windows during its decay process were captured with an intensified charge-coupled device (ICCD), and the temperature dependence of the ratio of fluorescence intensities in these two-time windows was calculated and calibrated. An optimal relative sensitivity of 5.03% K⁻¹ at 388 K was achieved in this scheme with a temperature resolution of about 0.3 K. Combined with fluorescence microscopy and the use of the ICCD, the temperature imaging of an operating printed circuit board with high spatial resolution was demonstrated by employing the temperature sensing scheme based on the time-resolved technique. The above results reveal that the InTaO₄:Cr³⁺ phosphor is very promising for applications in multi-mode high-sensitivity optical thermometry and temperature imaging.