Magnetic Properties of CoWN2 Synthesized by Ammonolysis of Nanocrystalline CoWO4 Materials

Abstract

We report a novel chemical methodology for the synthesis of nanocrystalline CoWN₂ which is stabilized by the induction effect. The methodology involves the nitridation of sol-gel-derived CoWO₄ precursor in nanocrystalline form using gaseous NH₃(g). We could obtain CoWN₂ as a nitrided product at both 700 °C and 750 °C with varied crystallinity. The synthesized materials were characterized using XRD, FESEM, EDS, and magnetic measurements. XRD studies confirm hexagonal CoWN₂ phase formation with a minor impurity phase which comprises of metallic Co. We have noted the values of lattice constants of CoWN₂ materials, i.e., a = 2.876(7) Å, b = 2.876(6) Å, c = 15.372(48) Å, and a = 2.872(3) Å, b = 2.872(2) Å, and c = 15.381(21) for the products synthesized at 700 °C and synthesized at 750 °C, respectively. The crystallite sizes are calculated as 11 ± 0.5 nm for CoWN₂ nanomaterials synthesized at 700 °C whereas 16 ± 0.5 nm for CoWN₂ nanomaterials synthesized at 750 °C. FESEM micrograph studies of CoWN₂ nanomaterials show nearly spherical particles. The average particle sizes obtained from FESEM images are 90 ± 5 nm for the nanomaterials obtained at 700 °C and 45 ± 2 nm for those obtained at 750 °C. Room temperature magnetic parameters, i.e., M_s and H_c for CoWN₂ materials synthesized at 700 °C are found to be 1.49 emu/g and 389 Oe, respectively, whereas for CoWN₂ materials (synthesized at 750 °C), the values marginally reduce to 0.06 emu/g and 375 Oe, respectively.