Exploring Laser-Induced Local Sintering in K(Y0.90Er0.05Yb0.05)3F10 Crystals through Luminescence Thermometry

Laser-induced heating is a groundbreaking tool across various fields, including medicine and micro/nanoscale material processing. Techniques such as laser ablation and sintering play pivotal roles in material processing. Laser sintering, in particular, drives critical processes, including particle coalescence, crystallinity enhancement, and densification, with precise temperature control essential to regulate sintering kinetics, grain boundary mobility, and phase stability. Luminescence thermometry is a promising approach for studying laser sintering, offering localized and real-time temperature measurements that surpass the limitations of traditional methods. This study explores laser-induced sintering in K(Y_0.90Er_0.05Yb_0.05)₃F₁₀ upconversion powder under 980 nm excitation at power densities of up to 275 W cm^–2. A pronounced transition from a nonemissive to a highly emissive regime is observed, driven by particle growth and enhanced crystallinity of the α-KY₃F₁₀ phase, as evidenced by X-ray diffraction and thermal analysis. Postirradiation, the transformed powder functions as a Boltzmann primary luminescent thermometer, enabling accurate temperature measurements up to 615 ± 32 °C. XRD data from the irradiated powder confirm the structural integrity of the α-KY₃F₁₀ phase, showing no new phase formation below 700 °C. By integrating local laser sintering with Boltzmann primary luminescent thermometry, this work demonstrates a scalable and robust method for real-time, localized temperature monitoring during sintering processes. These findings have significant implications for advancing additive manufacturing and other laser-based material processing techniques.