Synthesis and Fabrication of Co_1−xNi_xCr₂O₄ Chromate Nanoparticles and the Effect of Ni Concentration on Their Bandgap, Structure, and Optical Properties

• Main Authors: Muhammad Saeed, Malika Rani, Kiran Batool, Hafiza Batool, Aisha Younus, Sikander Azam, Arshad Mehmood, Bakhtiarul Haq, Thamraa Alshahrani, Ghafar Ali, Muhammad Maqbool
• Format: Article
• Language: English
• Published: MDPI AG 2021-09-01
• Series: Journal of Composites Science
• Subjects: synthesis; sol-gel process; cobalt chromite powder; XRD; photoluminescence
• Online Access: https://www.mdpi.com/2504-477X/5/9/247

In the present work, cobalt-chromite-based pigment Co_1-xNi_xCr₂O₄ chromate powder and nanoparticles with various transition metal concentrations (x = 0.2, 0.4, 0.6, and 0.8) were manufactured by applying aqueous synthesis approaches and sol–gel synthesis routes. XRD analysis of the powder shows that all samples formulated by the sol–gel method were crystalline with a spinel structure. Chromites show green color with a higher nickel concentration, while Co-substituent shows blackish pigments. Samples were annealed at distinct temperatures ranging from 600 °C to 750 °C. The nanoparticles obtained were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy (RS), photoluminescence (PL), and energy-dispersive X-ray spectroscopy (EDS). The particle size of the parent compound (CoCr₂O₄) ranges from 100 nm to 500 nm, as measured by SEM. The tendency of particles to form aggregates with increasing annealing temperature was observed. These compounds may be successfully used as an effective doped nickel-cobalt ceramic pigment.