**2.2 Material characterization**

The crystallinity of the phosphor was checked by X-ray diffraction estimation. The X-ray powder diffraction information was gathered by utilizing Bruker D8 Advanced X-ray diffractometer using Cu Kα radiation. The X-beams were created utilizing a fixed cylinder, and the wave length of X-beam was 0.154 nm. The X-rays were identified utilizing a quick checking indicator dependent on silicon strip technology (Bruker Lynx Eye finder). The surface morphology of the phosphors was detected by field emission electron microscopy (FESEM) JSM-7600F. Energy dispersive X-ray examination (EDX) was utilized for compositional investigation of the phosphor. Crystal size of arranged phosphor was determined by Transmission Electron Microscopy (TEM) utilizing Philips CM-200. Raman spectra were recorded by Jobin-Yvon, France, Ramnor HG-2S Spectrometer with Ar-Laser with 4 W control having goals of 0.5 cm<sup>−</sup><sup>1</sup> and wave number exactness of 1 cm<sup>−</sup><sup>1</sup> over 5000 cm<sup>−</sup><sup>1</sup> . XPS investigation was performed in a VG instrument with a CLAM2 analyzer and a twin Mg/Al anode. The weight pressure in the investigation chamber was roughly 9 × 10<sup>−</sup>10 mbar. The estimations were done with unmonochromated Al Kα photons (1486.6 eV). The intensity of the X-ray source was kept steady at 300 W.

**Figure 1.** *Flow chart of synthesis of Gd2O3 with urea (reproduced from [1]).*

**Figure 2.** *Flow chart of synthesis of Gd2O3 with glycerin (reproduced from [2]).*
