Synthesis, microstructural and optical characterizations of sol-gel grown gadolinium doped cerium oxide ceramics

Abstract

In this study, through the utilization of the sol–gel combustion tactic, gadolinium (Gd)-doped cerium oxide (CeO₂), Ce_1−xGd_xO₂ (x = 0.00, 0.10, 0.20 and 0.30 (GDC)) ceramics were attained. The synthesized GDC ceramics were investigated using X-ray diffraction (XRD) to scrutinize their crystal structures and phase clarities. The obtained GDC ceramics have a single-phase cubic structure and belong to the crystallographic space group fmm (225). The measurement of the diffraction angle of each reflection and the subsequent smearing of the renowned Bragg's relation provided coarse d-interplanar spacings. The stacking fault (SF) values of pure and Gd-doped CeO₂ ceramics were assessed. To muse the degree of preferred orientation (σ) of crystallites along a crystal plane (h k l), the texture coefficient (C_i) of each XRD peak of GDC ceramics is gauged. By determining the interplanar distance (d_{h k l}), the Bravais theory sheds light on the material's development. By exploiting Miller indices for the prime (1 1 1) plane, the lattice constants of GDC ceramics and cell volumes were obtained. Multiple techniques were employed to ascertain the microstructural parameters of GDC ceramics. A pyrometer substantiated the density of GDC ceramics. The room temperature (RT) Fourier transform infrared (FTIR) spectra of both un-doped and Gd-doped CeO₂ were obtained. The UV-vis-NIR spectrometer recorded the GDC ceramics' reflectance (R) spectra at RT. For both undoped and Gd-doped CeO₂, the absorption coefficient (α) spectra showed two distinct peaks. The R-dependent refractive index (η) and the α-dependent extinction coefficient (k) were determined for all GDC samples. The optical band gap (E_g) was obtained by integrating the Tauc and Kubelka–Munk approaches for GDC ceramics. For each GDC sample, the imaginary (ε_i) and real (ε_r) dielectric constants, as well as the dissipation factor (tan δ), were determined local to the characteristic wavelength (λ_c). Calculations were made for the Urbach energy (E_U) and Urbach absorption coefficient (α₀) for GDC ceramics. The minimum and maximum values of optical (σ_o) and electrical (σ_e) conductivity for GDC ceramics were determined. The volume (VELF) and surface (SELF) energy loss functions, which depend on the constants ε_i and ε_r, were used to measure electrons' energy loss rates as they travel across the surface. Raman spectroscopy revealed various vibrational modes in GDC ceramics. Finally, the implications are discussed herein.