Cr<sup>3+</sup>-Sphere Effect on the Whitlockite-Type NIR Phosphor Sr<sub>9</sub>Sc(PO<sub>4</sub>)<sub>7</sub> with High Heat Dissipation for Digital Medical Applications
Chun-Han Lu, Yi‐Ting Tsai, Tzong‐Liang Tsai, Ting‐Shan Chan, Xuejie Zhang, Chun Che Lin
Abstract
The analysis of human body composition and food composition requires high-efficiency broadband near-infrared (NIR) lighting sources to achieve a portable, appropriately sized equipment. Herein, we develop a whitlockite-type NIR phosphor Sr9Sc(PO4)7:Cr3+ with an emission centered at 860 nm and full width at half-maximum of 147 nm. Due to the structural characteristics of the matrix, the 60 mol % Cr3+ substitution at the Sc3+ sites gives an internal quantum efficiency up to 56.5%. By replacing Sr with Ba and Ca, we observe a nontypical spectral shift phenomenon and discuss the influence of the second-sphere effect on octahedral Cr3+ ions. To evaluate the diagnostic application, we design a NIR ceramic device with a high optical power of 27.38 mW and high heat dissipation, which can decrease surface working temperature by nearly 50 °C for digital intraoral application. This study provides the research of the second-sphere coordination effect for selective octahedral sites such as Ca, Sr, and Ba coordinated by O atoms on a whitlockite-type crystal. Furthermore, the device promotes a nonionizing solution for detecting dental caries, tooth calcification, and diagnostic application.