Microcube formation and characterization of cobalt and nickel selenite dihydrate: Thermal, spectral, and dielectric insights

Abstract

This paper outlines the template-free preparation of cobalt and nickel selenite dihydrate microcubes using a simple precipitation method from aqueous solutions at room temperature. Structural analysis revealed the formation of pure, well-crystallized isostructural cobalt and nickel selenite dihydrate, exhibiting monoclinic crystal systems of space group P21/n. Thermal analysis showed distinct decomposition patterns for both compounds, highlighting their thermal stabilities. The intermediate formed after water loss were stable up to ∼550 °C, and crystallized before decomposing into their respective oxides via SeO2 sublimation. Scanning electron microscopy (SEM) images illustrated the presence of irregular-sized well-defined microcubes with smooth surfaces and sharp edges, distributed across the material. The formation of these microstructures is likely driven by self-aggregation and the Ostwald ripening process. Dielectric studies on pelletized materials revealed higher dielectric constants at low frequencies with minimal dielectric loss. CoSeO3⋅2H2O exhibited higher dielectric constants than NiSeO3⋅2H2O due to the larger ionic radius of Co2+ ions, which leads to a greater degree of polarization compared to Ni2+ ions. The considerably higher dielectric constant with an insignificant amount of dielectric loss indicates the materials’ potential for applications in dielectric and microwave technologies.