Nanocrystalline powder with particle size 50 nm and thin film with thickness 2 μm of SrBi2Ta2O9 (SBT) were successfully prepared by the sol–gel method, using strontium acetate semihydrate [Sr(CH3COO)2.1/2H2O] and bismth subnitrate [BiO(NO3)], and tantalum ethoxide [Ta(OCH2CH3)5] as source materials, glacial acetic and ethylene glycol as solvents. The XRD and TEM results indicated that SBT layer-perovskite phase powder obtained has to be single phase, Pt layer had a (100) predominate orientation, and the (115), (200) of SBT thin film formed after being annealed at 800 ℃ for 1 min. The typical hysteresis loop of SBT thin film on Pt/Ti/SiO2/Si was obtained, and the measured Pr and Ps values of the SBT thin film were 5.5 and 8.8 μC/cm2, respectively.

The mechanical properties and microstructure of SiC ceramics, hot pressed by simultaneously adding nano-SiC and oxides (MgO+Al2O3+Y2O3) or nitrate salts (Mg(NO3)2+Al(NO3)3+Y(NO3)3) as additives, were evaluated. The oxide additives system slightly influenced the mechanical properties of the ceramics, while the addition of nano-SiC lead to finer microstructure, and 5 vol.% nao-SiC changed the fracture mode from intergranular type to transgranular type. The ceramics with nitrate salts had fine, equiaxed grains with an average grain size larger than that of the system added oxides, thus inducing lower Viker’s hardness and flexural strength, while the presence of crystalline YAG phase improved the fracture toughness by 54.7%. Also, an observed increase in grain growth—with decreasing weight fraction of liquid and the grounded grain morphology in this system—confirmed a diffusion-controlled growth mechanism. Although the sample with the least amount of additives has the lowest relative density and largest grain size, its flexural strength did not drastically decrease. The influence of nano-SiC on the fracture toughness in the nitrate additive system was negligible.

LiTaO3/Al2O3 ceramic composites were fabricated by hot pressing and pressureless sintering, respectively, to investigate the effect of piezoelectric secondary phase on the properties of structural ceramics. Phase constitution, microstructure and mechanical properties of the ceramic composites were studied. LiTaO3 could stably coexist with Al2O3 during sintering. LiTaO3 phase was located at the grain boundaries of Al2O3 matrix fabricated by different processing routes. Domain structures were clearly seen in LiTaO3, confirming that LiTaO3 remained hexagonal ferroelectric phase. About 5 vol.%LiTaO3/Al2O3 ceramic composite prepared by pressureless sintering at 1300 ℃ showed an increase in fracture toughness. Energy dissipation due to domain switching was suggested as a toughening mechanism. With the increasing of LiTaO3 content, the domain switching toughening mechanism was decompensated by the decreased relative density of LiTaO3/Al2O3 ceramic composites. For LiTaO3/Al2O3 ceramic composites prepared by hot pressing at 1500 ℃, the bending strength decreased because of the increased grain size of Al2O3 matrix. The toughening effect due to domain switching was also decompensated by the coarsening of Al2O3 matrix grains, the weaker net-like LiTaO3 phase and the weaker bonding strength between LiTaO3 phase and Al2O3 matrix.

An alloy Al-12wt.% Ti-6wt.% Nb was prepared by mechanical alloying (MA) process and its microstructure, mechanical properties and thermal stability were investigated. It was shown that the MA Al-12Ti-6Nb is an Al matrix composite with uniformly distributed intermetallic Al3Ti dispersoids and single phase Nb flakes as well as fine equiaxed Al2O3 and rod-shaped Al4C3 phases. In most of the Al3Ti particles, especially the large ones, island-shaped α-Ti cores are normally retained. After exposure at 550℃ in air for 200h, the Al3Ti dispersoids coarsen slowly and their α-Ti cores disappear, while the single phase Nb remains. Compared with the MA Al-12Ti fabricated in the same way, the MA Al-12Ti-6Nb shows much more excellent mechanical properties and thermal stability, which can be attributed to the more effective reinforcement of Al3Ti dispersoids and Nb flakes due to the alleviation of their thermal expansion mismatch with the Al matrix by the addition of Nb.

Coexisting LiTaO3/Al2O3 ceramic composite was hot pressed at 1573 K. The highest values of flexural strength and fracture toughness reached 492.9 MPa and 5.3 MPam1/2, respectively, for the composite containing 15 vol.% LiTaO3. Domain switching which was clearly discerned near the crack tip in LiTaO3 grains is suggested as a new toughening mechanism in structural ceramics.