Color Tunability and Optical Thermometry Study of Er³⁺-Codoped SrMoO₄:Dy³⁺ Phosphor

Rare-earth-based luminescence thermometry and multiplying demand for adjustable color-emitting phosphors have been pushed nowadays. The objective is to develop a suitable phosphor, a highly stable contactless temperature sensor with high sensitivity, and good temperature-induced color discriminability with a cost-effective synthesis technique. In this study, SrMoO4-based phosphors were successfully synthesized via a cost-effective and facile autocombustion approach. Structural analysis confirmed the tetragonal structure and I41/a space group of products validated with JCPDS card number 08-0482. Detailed spectroscopy analysis revealed enhanced photoluminescence (PL) properties for 4 at% of Dy3+-doped and 3 at% of Er3+-codoped content in a series of SrMoO4:xDy3+, yEr3+ (x = 1, 3, 4, and 5 at%; y = 1, 2, 3, and 4 at%) phosphors. CIE coordinates were observed at the cryostat region and room temperature. Based on temperature-dependent luminescence properties and analyzing them using the fluorescence intensity ratio technique, the relative sensitivity (SR) value reached 1.42% K–1, 1.72% K–1, and 0.91% K–1 at 300 K for non-thermally coupled levels. Similarly, 0.08% K–1 and 0.77% K–1 are due to transitions 4S3/2 → 4I15/2 and 4F9/2 → 6H11/2, respectively, at low temperature for thermally coupled levels. As defined, thermally and non-thermally coupled levels exhibit interesting results with the rise in temperature for optical thermometry application. Temperature-dependent photoluminescence (TDPL) analysis shows that different excitation wavelengths and varying temperatures result in different emission wavelengths, as in color tunability applications. The results of our study demonstrate the suitable application as a color-tunable device and a temperature sensor.