Impact of Ni doping into Co2SiO4 compound: Synthesis, structural, morphological, dielectric, optical, photoluminescence, and magnetic properties

The fabrication and characterization of orthosilicate compounds have received great interest due to their unique optical and magnetic features, and numerous fundamental and technological applications. Herein, a series of Ni doped cobalt orthosilicate compounds, Co2-xNixSiO4 (x = 0.0, 0.1, 0.3 and 0.5) were fabricated via ceramic route by sintering the processed powder at high temperatures. The powder X-ray diffraction results revealed that these compounds crystallize in the orthorhombic symmetry with crystallite size ranging from 29 to 56 nm. Fourier transform infrared and Raman spectra support the phase pure formation of these compounds in the orthorhombic structure. The micro images illustrate a wide range particle size distributions, and elemental analysis affirms the right stoichiometry of these compounds. The dielectric constant and loss angle tangent spectra over the broader frequency range of 101-109 Hz reveal the fundamental polarization and relaxation characteristics of dielectric ceramics. Frequency dependent alternating current electrical conductivity and analysis of UV-Vis reflectance spectra exhibit the wide band gap semiconducting behaviour which establish uses of these compounds in futuristic power electronic module and optoelectronic devices. The fluorescence spectra show a little shift towards the lower wavelength in the emission band by increasing the Ni concentration in the compound. Additionally, the CIE coordinates explain that the blue-violet emission from these compounds, make them useful for cutting edge luminescent devices. Magnetic characterization identified the antiferromagnetic to paramagnetic transition (TN) in these compounds, together with a decrease in TN from 50 K (x = 0.0) to 38 K (x = 0.5). The low temperature (10 K) magnetic hysteresis loops confirm the existence of strong antiferromagnetism with weak ferromagnetism. The presence of two p-type semiconductors (cobalt oxide and nickel oxide) play an important role between magnetic and semiconducting properties of these compounds, and make them good candidates for magnetic semiconductor spintronic devices.