Comment on “Charge Transfer-Triggered Bi<sup>3+</sup> Near-Infrared Emission in Y<sub>2</sub>Ti<sub>2</sub>O<sub>7</sub> for Dual-Mode Temperature Sensing”
Hei‐Yui Kai, Longbing Shang, Ka‐Leung Wong, Chang‐Kui Duan, Peter A. Tanner
Abstract
Undoped Y 2 Ti 2 O 7 exhibits impurity emission bands at low temperatures due to Mn 4+ and Cr 3+, as established by codoping with these ions. Contrary to a recent report by Wang et al., ACS Appl. Mater. Interfaces 2022, 14, 36834–36844, we do not observe Bi 3+ emission in this codoped host, as also is the case for Fe 3+ . The emission reported in that paper as being due to Bi 3+ in fact corresponds to Cr 3+ emission. The Cr 3+ and Mn 4+ emissions are quenched with increasing temperature, so that Mn 4+ emission is scarcely observed above 80 K. We present variable temperature optical data for Y 2 Ti 2 O 7 and this host codoped with Mn, Cr, Fe, and Bi, as well as a theoretical justification of our results.