Diethylene glycol mediated synthesis of Gd2O3:Eu3+ nanophosphor and its Judd–Ofelt analysis

Gd1.9Eu0.1O3 nanophosphor with enhanced photoemission is successfully synthesized by a controlled combustion method of metal–citrate complex in diethylene glycol medium. It is found that the phase formation and spectral properties including quantum efficiency are highly sensitive to sintering temperature and the role of citric acid both as a chelating agent and as a fuel for combustion was evident in the study. The formation of cubic Gd2O3:Eu nanocrystalline phosphor was confirmed by X-ray diffraction, Raman and Infrared measurements. Transmission electron microscopic images together with the SAED patterns indicate the formation of spherical Gd2O3 nanocrystalline powder with well defined planes separated by 0.312 nm of cubic Gd2O3. The high degrees of homogeneity observed in the electron micrographs are attributed to the glycol medium used. The intensities of transitions between different J levels depend on the symmetry of the local environment of Eu3+ activators and are described using the Judd–Ofelt analysis. The spectral properties of the samples prepared under optimum conditions have shown large asymmetric ratio, indicating high degree of distortion in local environment around Eu3+ ions and a maximum quantum efficiency of 78% was obtained. The life-time measurements indicated an increase from 0.83 to 1.28 ms with increase in sintering temperature from 700 to 1000 °C. The chromaticity and correlated colour temperature of the emission were evaluated based on the 1931 CIE chromaticity diagram. The absorptions observed in the excitation spectra show the suitability of the nanophosphor obtained in this study for getting excited in UV, NUV and visible regions for a variety of device applications.