Effect of Flux and Host Modification on the Properties of Y₃Al₅O₁₂∶Dy³⁺ for Optical Thermometry

Herein， Y3Al5O12∶Dy3+ was synthesized by high-temperature solid-state method after adding different fluxes （such as H3BO3， fluoride， chloride， carbonate， etc.） and adjusting matrix ions （partial substitution of Y3+ or Al3+ with Lu3+， Ca2+， Zr4+， Si4+， etc.）. The structure， morphology， photoluminescence properties and temperature measurement properties of the synthesized phosphors were systematically investigated. In terms of flux optimization， the addition of 2% （mass percent） H3BO3 was observed to enhance the crystallinity and improve the luminescent intensity of the phosphors. Regarding host ion regulation， among all modified samples， Lu2Y0.96Al5O12∶0.04Dy3+， where Y3+ was partially substituted with Lu3+， exhibited the strongest luminescence. Under 353 nm ultraviolet excitation， as the temperature increased from 298 K to 1073 K， the intensity of the 483 nm emission peak （4F9/2→6H15/2） decreased while that of the 456 nm peak （4I15/2→6H15/2） increased. Utilizing the fluorescence intensity ratio （FIR） of these two thermally coupled energy level transitions enabled optical temperature measurement over a wide temperature range. Specifically， the maximum relative sensitivities of Y3Al5O12∶Dy3+ phosphor with 2% H3BO3 added and Lu2Y0.96Al5O12∶0.04Dy3+ phosphor with matrix ion substitution reached 0.7317%/K （at 378 K） and 0.7483%/K （at 398 K）， respectively， and their maximum absolute sensitivities were 0.00086 K-1 （at 918 K） and 0.00085 K-1 （at 958 K）， respectively. Due to the influence of temperature change， the electrons on the thermal coupling energy level are redistributed， and the emission lifetime of Lu2Y0.96Al5O12∶0.04Dy3+ phosphor at 483 nm is shortened from 0.405 ms at 298 K to 0.314 ms at 1073 K. These results provide experimental basis and optimization strategies for the design and improvement of high-sensitivity optical temperature sensors with wide temperature ranges.