“…It shows polymorphism exhibiting α, β, γ, δ, and ε forms and a recently reported κ form. , Moreover, owing to its electronic properties, optical properties, as well as significant chemical and thermal stability, it finds applications in catalysts, phosphors, electroluminescent devices, and gas sensors. , As one of the previously introduced polymorphs, spinel-type γ-Ga 2 O 3 exhibits intrinsic Ga vacancies in both tetrahedral and octahedral sites, as reported by Playford et al Therefore, γ-Ga 2 O 3 can be an efficient host accommodating and replacing a transition metal or rare-earth metal element, which can further broaden its application scope. In recent years, spinel-type Ga-based metal oxides such as FeGa 2 O 4 , CuGa 2 O 4 , CdGa 2 O 4 , and ZnGa 2 O 4 have been studied for use as magnetic materials, gas sensors, photocatalysts, and transparent conductors. − As a spinel-type Ga-based metal oxide, CoGa 2 O 4 has been considered for applications in ceramic pigments, p-type semiconductors, gas sensors, electrocatalysts, , and cathodes and anodes for various types of capacitors − owing to its superior conductivity, electrochemical activity, and energy storage capability. It has a partially inverse structure, as shown in Figure , where divalent and trivalent cations, that is, Co 2+ and Ga 3+ , occupy both tetrahedral and octahedral sites.…”