Correlated structural and optical properties of crystal-engineered Eu3+-doped gadolinium oxyfluoride polymorphs compatible for lighting and display applications

Abstract

Functional materials exhibiting polymorphism serve as excellent candidates for various optical applications since the properties can be tuned to the desired target/application by modifying the structural features. Herein, we explored the synthesis of Eu3+ doped gadolinium oxyfluoride systems via a green microwave-assisted hydrothermal method, and phase controllability was established by varying the O2− to F- ratio. The phase evolution and crystal structure of the Eu3+ doped oxyfluoride analogs were examined using Rietveld refinement studies, and the results were consistent with the site symmetries unveiled by the photoluminescence spectra of Eu3+. The low phonon energy of all the phosphors, calculated from the Raman spectra, suggested the possibility of these groups of materials as excellent host matrices for optical applications. Further, a drastic variation in the morphology of studied oxyfluorides at different phases is evidenced by the electron microscopic analysis. The highly asymmetric rhombohedral sites enhanced the color purity, lifetime, and quantum yield of the red phosphor, making it an excellent red component for the fabrication of UV-excitable red as well as white light-emitting diodes for lighting and display device functionalities.