HARDNESS AND ETCHING STUDIES ON FLUX GROWN YFEO3 CRYSTALS

Results of Vicker's microhardness(Hv), fracture toughness(Kc), brittleness(Bi) and dislocation etching characteristics on (110) and (001) planes of flux grown yttrium orthoferrite crystals are reported. The values of Hv, Kc, Bi are estimated to be 1235.08Kg/mm2, 0.1912gm/mu-m3/2 & 8.1955-mu-m-1/2 respectively for (110) plane whereas for (001) plane the values of Hv, Kc & Bi are 1027.12kg/mm2, 0.5975gm/mu-m3/2 and 1.8757-mu-m-1/2 respectively. The variation of Hv with applied load is explained to follow from Hays and Kendalls law. Etching kinetics of YFeO3 surfaces in H3PO4 at different temperatures leads to activation energy values for etch pits; the activation energies for dissolution parallel to (110) and (001) planes (i.e., lateral dissolution E(L)) are 0.41ev and 0.34ev respectively. The activation energies for dissolution perpendicular to (110) and (001) planes (i.e., vertical dissolution E(D)) are 0.20ev and 0.21ev respectively.