Tunable Upconversion Luminescence and Optical Thermometry in (Yb,Er)2SiO5/SiO2 Composite Phosphors

Upconversion luminescent materials have broad application prospects in lighting, display, and laser technology. However, single-phase systems are constrained by performance bottlenecks, making it difficult to simultaneously achieve high temperature sensitivity and tunable luminescence. To address this challenge, (Yb x Er 1-x ) 2 SiO 5 /SiO 2 multiphase composite phosphors are synthesized using a low-temperature (300 °C) hydrothermal method. Under 976 nm excitation, the material exhibits concentration-dependent luminescence: as the Yb fraction increases, the red emission at 660 nm continuously enhances, while the green emission shows initial enhancement followed by suppression. This behavior is attributed to an energy back-transfer mechanism between Yb 3+ and Er 3+ ions. Regarding temperature sensing, a highly repeatable thermal response is observed through the fluorescence intensity ratio of Er 3+ levels. Specifically, the thermally coupled levels show a relative sensitivity of 1.91% K −1 , while the non-thermally coupled levels exhibit an absolute sensitivity of 0.1063 K −1 . Furthermore, precise adjustment of Yb 3+ content, excitation power, or temperature enables continuous color tuning from green to red. This work simultaneously realizes high-precision temperature sensing and dynamic luminescence color control in upconversion materials, providing novel design concepts and practical pathways for developing multifunctional optical materials.