Magnetic Properties of Cobalt-Based Carbide Particles Synthesized by the Polyol Process

Single-phase Co carbide particles with the Co
₃
C structure were obtained by the polyol process using tetraethylene glycol (TEG) solution containing polyvinylpyrrolidone (PVP). Additionally, particles with a mixture of face-centered cubic Co and hexagonal close-packed Co were precipitated in the TEG solution without PVP. The particles synthesized with PVP exhibited coercivity of about 5.7 kOe, which was larger than that of the particles synthesized without PVP. Thus, the addition of PVP to the TEG solution induces the formation of Co
₃
C-structured Co carbide particles with large coercivity. Particles precipitated from the TEG solution with an initial molar ratio of Co:Ni = 8:2 were also identified as the single phase of the Co
₃
C structure by X-ray diffraction measurement. In addition, it was confirmed by measurements of the extended X-ray absorption fine structure spectra that Ni atoms in the precipitated particles had a local structure similar to that of Co atoms in the single-phase particles with the Co
₃
C structure. Thus, Ni-substituted Co carbide particles with the Co
₃
C structure can be obtained by the polyol process using PVP.