Dy-B-Si-O glass-doped Ba0.6Sr0.4TiO3 (BST) ceramics based on sol-gel-derived powders were prepared. Effects of B2O3-SiO2 in Dy-B-Si-O glass on phase structure, microstructures and dielectric properties of the BST ceramics were investigated. The results showed that the main crystal phase of BST ceramics with appropriate B2O3-SiO2 in Dy-B-Si-O glass had a perovskite type structure. Grain size decreased and density increased compared with pure BST ceramics. However, the secondary phase Ba2TiSi2O8 was detected when the percentage of B2O3-SiO2 in Dy-B-Si-O glass additive was over 7 mol%, and increased with the increasing of B2O3-SiO2. With the increasing of B2O3-SiO2, the dielectric constant increased firstly and then decreased, the dielectric loss decreased firstly and then increased, the Curie temperature moved to lower temperature firstly and then to higher temperature.
Nb2O5-7.5La2O3-Al2O3 composite ceramics were prepared by microwave sintering. The influence of Nb2O5 and La2O3 proportion on the microstructure and mechanical properties of Al2O3 ceramics was investigated. The results show that when the Nb2O5 content was lower than La2O3, the columnar LaAl11O18 grains were generated by the reaction of La2O3 with Al2O3. When the Nb2O5 content was higher than La2O3, the surplus Nb2O5 induced the formation of columnar Al2O3 grains. The growth of columnar Al2O3 grains were promoted synergistically by LaNbO4 formed in-situ and Nb2O5. The 5Nb2O5-7.5La2O3-Al2O3 composite ceramic exhibited excellent comprehensive properties: ρr=99.3% (relative density), HV=11.2GPa (microhardness), KIC= 6.4MPa·m1/2 (fracture toughness), σ=304.3MPa (bending strength).
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