Study On Compositions And Processing Techniques Of Black Alumina Ceramics

In order to improve application character of black alumina packing ceramics, assure coloring effect, decrease dielectric loss and lower sintering temperature, colorants of Fe2O3,CoO,NiO,MnO2 and sintering aids of AST (1/3Al2O3: 3/4SiO2: 1/4TiO2) were added to 91wt%Al2O3. The effect of additives, the content of AST and process procedure on the properties of alumina ceramics has been investigated. The samples would reveal black color when Fe2O3 content is less than 4% and CoO content is less than 1%. The additives of MnO2,NiO were facilitated forming glass phase and lowering sintering temperature of alumina. The dielectric properties and coloring effect of sintered samples with presynthesis of transitional metal oxide procedure were better than the samples with one-step procedure. It was identified by XRD analysis that transitional metal oxide exist in black alumina ceramics as the mixed spinel crystal structure. The volume resistivity is lower than 1010Ω.cm when the AST content is less than 3.5% or more than 11.5%. It can be conclude that the best properties was obtained when sintered 91% alumina ceramics at 1350℃with Fe2O33%,CoO0.5%,NiO1%,MnO2 2% colorants and 4%AST sintering aids. The parameter of black alumina ceramics are listed below: volume resistivity (1012Ω.cm), dielectric constant (14.2), dielectric loss (0.012).