Insights into the crystal structure and photophysical response of Dy3+ doped Li3Y3Te2O12 for ratiometric temperature sensing

Temperature sensors based on non-contact thermometry with better accuracy and efficiency are inevitable in various fields. In this work, a detailed study on the crystal structure and temperature dependant photophysical response of the tellurate garnet, Li3Y3Te2O12: Dy3+, is done for the first time. The crystal structure and the substitution of Dy3+ ion at the dodecahedral site of Li3Y3Te2O12 were confirmed using Rietveld refinement of the XRD patterns and Raman spectra. The characteristic sharp yellow and blue bands of Dy3+ were obtained under an excitation of 352 nm. The intense yellow band corresponding to the electric dipole transition is used to confirm the dodecahedral site occupancy of Dy3+. Moreover, an increase in the Y/B ratio (intensity of yellow to blue bands) indicates a larger degree of covalence between Dy3+ and O2− ions in the Li3Y3Te2O12 matrix. In addition, concentration quenching is caused by the exchange interaction between Dy3+ ions. Also, the decrease in decay time with higher concentrations is observed due to the enhancement in nonradiative energy transfer. The CIE coordinate of the optimum concentration is (0.39, 0.40), corresponding to the yellow region. The fluorescence intensity ratio is used to evaluate the temperature sensing properties based on the distinct fall of emission bands in the temperature range 80–300 K. A maximum relative thermal sensitivity of 1.2%/K is obtained at 80 K. These results point out that the as-prepared phosphor Li3Y3Te2O12: Dy3+ can be used as a potential candidate for ratiometric temperature sensing at low temperatures.