Structural, dielectric, optical, photoluminescence, and magnetic features of olivine type Co₂SiO₄ compound

Orthosilicate compounds are the olivine structured transition-metal silicates, which are technologically established in the advances of luminescent and spintronic devices, and electrode materials for lithium ion batteries. In the present study, cobalt orthosilicate compound Co₂SiO₄ was synthesized through solid state reaction process by sintering the powder at 1170 °C for 8 h. A comprehensive analysis of powder X-ray diffraction data showed that the compound crystallizes in the Pbnm space group of orthorhombic symmetry with cobalt atoms in octahedral and silicon atoms in tetrahedral environments. Fourier transform infrared bands and Raman mode analyses further confirm the formation of this compound in orthorhombic structure. Morphological and elemental analysis substantiate the right stoichiometry of the synthesized Co₂SiO₄ material. The dielectric constant and loss angle tangent spectra in the broader frequency range of 10¹ to 10⁹ Hz show the fundamental polarization trend of dielectric ceramics. The electronic transitions observed in the visible region of the UV-Vis reflectance spectrum correspond to the d-d transition of Co²⁺ ions in octahedral crystallographic arrangement. The photoluminescence spectroscopic analysis and the CIE coordinates suggest that the blue-violet emission from the Co₂SiO₄ compound could be useful for development of advanced luminescent devices. Magnetic measurements showed paramagnetic features of this compound at room temperature together with a transition from paramagnetic to antiferromagnetic at 50 K, superimposed with weak ferromagnetism. A low temperature (10 K) magnetic hysteresis explains weak ferromagnetic like behavior of the Co₂SiO₄ compound arising from uncompensated surface spins. The negative Weiss temperature value of about − 59 K substantiates the strong antiferromagnetic exchange interactions. The effective paramagnetic moment 3.89µ_B is found close to the spin only value 3.87µ_B of Co²⁺ ion (S = 3/2).