Wang Yuming, Darapaneni Pragathi, Kizilkaya Orhan, Dorman James A
Cain Department of Chemical Engineering , Louisiana State University , Baton Rouge , Louisiana 70803 , United States.
Center for Advanced Microstructures and Devices , Louisiana State University , Baton Rouge , Louisiana 70806 , United States.
Inorg Chem. 2020 Feb 17;59(4):2358-2366. doi: 10.1021/acs.inorgchem.9b03226. Epub 2020 Jan 28.
YZrO (YZO) is widely used as a host material for luminescent centers because of its high stability and the ability to accommodate anion defects. In this work, the effects of Ce and Tb doping on the photoluminescence (PL) properties of YZO nanoparticles (NPs) are studied in detail to correlate the emission intensity with the dopant concentration. Herein, a two-step synthesis method of coprecipitation and molten salt was employed to prepare the YZO:Tb,Ce NPs. The single doped YZO:Tb (2 mol %) NPs shows a strong Tb emission. However, after codoping with Ce ions, the Tb emission is quenched instead of the expected sensitization. To identify the mechanism of quenching (oxidation state/local symmetry), X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) were performed. The Ce ions were observed to drive further oxidation of Tb to a nonluminescent +4 oxidation state. Alternatively, Eu was employed to probe local symmetry changes upon Ce doping. The asymmetry ratio of the magnetic and electronic transitions indicates that the Ce dopant also pushes the system into a higher symmetry, resulting in two separate quenching mechanisms.
