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Abstract: Highly densified Al2O3/LiTaO3 (ALT) ceramic composites were fabricated by hot-pressing in a nitrogen atmosphere. The addition of Al2O3 particles could significantly improve the densification of LiTaO3. Sintering mechanism of the LiTaO3 ceramic incorporated with Al2O3 particles is proposed. Dielectric constant of 5vol.% Al2O3/LiTaO3 (5ALT) composite ceramic was slightly increased in the range from 30kHz to 106 Hz, but the dielectric loss was lowered in the whole range from 103 Hz to 106 Hz. Piezoelectric constant (d 33) of the 5ALT ceramic composite is about 50% of that of LiTaO3 single crystal. [Copyright &y& Elsevier]

Abstract: Porous silicon nitride/silicon oxynitride composite ceramics were fabricated by silica sol infiltration of aqueous gelcasting prefabricated Si3N4 green compact. Silica was introduced by infiltration to increase the green density of specimens, so suitable properties with low shrinkage of ceramics were achieved during sintering at low temperature. Si2N2O was formed through reaction between Si3N4 and silica sol at a temperature above 1550°C. Si3N4/Si2N2O composite ceramics with a low linear shrinkage of 1.3–5.7%, a superior strength of 95–180MPa and a moderate dielectric constant of 4.0–5.0 (at 21–39GHz) were obtained by varying infiltration cycle and sintering temperature. [Copyright &y& Elsevier]