Aluminum oxide powders doped with MgO (300 to 500 nm) were sintered to almost theoretical density within just 10–15 min at 1150 °C using a plasma-activated sintering process based on charging the loosely filled powders with an electric discharge prior to densification by resistance heating. The microstructure of the consolidated disks was examined by high resolution transmission electron microscopy (HREM) and electron energy loss spectroscopy (EELS) and revealed excellent grain to grain contact with virtually no grain growth and structurally clean grain boundaries.

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supercooled meits was conducted. Supercooled melts and quenched glasses have high viscosity resulting in low diffusion rates that hinder the growth of the crystalline phases. The optimum supercooling for the formation of t h e 2223 phase in Bi-Pb4r-Ca-Cu-O glasses was determined by our experiments to be -6OO0C. Avrami exponents were calculated for t h e phase transformation of the supercooled melts to superconducting 2212 and 2223 phases; similar exponents were obtained for t h e 2223 phase crystallized from powders of quenched glasses. The morphology of crystallized Dhases in all SamDleS was observed by scanning electron microscopy.

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