SYNTHESIS OF CrO2 MODIFIED c-ZrO2 OF FERROMAGNETIC NANOCOMPOSITE PARTICLES

Ferromagnetic nanoparticles when dispersed in a dielectric ceramic matrix offer a new series of percolation composites with a metal-semiconductor or insulator interface that tailors the functional properties. In this purview, ZrO2 of a high dielectric constant (epsilon(r)) is stabilized in a cubic (c) polymorph by incorporating CrO2 of strongly ferromagnetic nanoparticles. A selective composition 20CrO(2) - 80ZrO(2) is synthesized after heating a polymer precursor with glycerol at 500 degrees C - 800 degrees C in air for 2 h. Broadening of X-ray differction peaks reveals Cr4+: c-ZrO2 with an average crystallite size 5 nm in the 500 degrees C heated sample and that is grown to 8 nm on increasing the temperature to 800 degrees C. They occur as bundles of thin platelets in electron microscopic images. Both the samples have ferromagnetic hysteresis loops with 794 and 211 Oe of coercivities, respectively. Variations of epsilon(r)-value and the power loss are studied as a function of frequency f (50 Hz 100 kHz range) on cold-pressed pellets at selective temperatures, in the 30 degrees C - 500 degrees C range, in describing the erects of the magnetic species.