Multifunctional applications of gadolinium-doped cerium oxide (Ce1–Gd O2–∂) ceramics: A review

Cerium oxide (CeO2), or ceria, and its doped derivatives have been extensively studied for several decades and are well-known oxides valued for their unique structural properties and wide range of applications. These materials play a crucial role in sustainable development within society. Structural modification through defect engineering of the highly stable cubic fluorite phase enhances the versatility of this doped ceria to a new level. Among the numerous dopants of the CeO2 matrix, ceria doped with the rare earth metal gadolinium (Gd), known as Ce1–xGdxO2–∂ (CGO), is gaining popularity due to its multifunctionality. The introduction of defect-induced vacancies in the oxygen sublattice (VO) and a change in the average valence of cerium (Ce3+/Ce4+) are primarily responsible for the improved performance compared to pristine CeO2. These materials are currently undergoing intensive research for potential use as electrolytes in intermediate-temperature solid oxide fuel cells (IT-SOFCs) and dense oxygen-permeable membranes (OPMs). Additionally, they are being commercially utilized for power generation and oxygen separation. CGO materials are also attracting significant attention in various fields such as optics, photocatalysis, electrostriction, spintronics, gas sensing, electrocatalysis, and biomedical applications. This review paper aims to compile the latest contributions to CGO materials and comprehensively cover their various application areas. The crystal structure, defect equilibrium in Gd3+-doped CeO2, the origin of multifunctionality, and the prospects of these materials are also exclusively discussed.