La0.6Sr0.4Co0.8Fe0.2O3 was synthesized by a citrate method, and the contributing factors to the formation of homogeneous fine powder with a pure perovskite-type structure were ascertained. The obtained La0.6Sr0.4Co0.8Fe0.2O3 exhibits superior sinterability and mixed electronic-ionic conduction properties than that synthesized by a traditional solid state reaction method.

properties of (Na0.5Bi0.5)0.94Ba0.06TiO3 are more sensitive to poling temperature due to the relatively low depolarization temperature. Moderate increase of sintering temperature improved the poling process and piezoelectric properties due to the development of microstructural densification and crystal structure. With respect to sintering behavior and piezoelectric properties, a sintering temperature range of 1130-1160℃ was ascertained for (Na0.5Bi0.5)0.90Ba0.10TiO3.

(Na0.5Bi0.5)1-xBaxTiO3 powders were synthesized by a citrate method, and the piezoelectric and ferroelectric properties of the ceramics were investigated. The results indicate that the citrate method is an advantageous alternative route to the conventional method in producing (Na0.5Bi0.5)1-xBaxTiO3 ceramics. Homogeneous and fine powders with a pure perovskite structure were derived from precursor solutions with a mole ratio of citric acid to total metal cation content (C/M) of 1.25 by calcining at 600℃ for 1h. The ceramics made by the citrate method exhibit superior piezoelectric properties near the rhombohedral-tetragonal morphotropic phase boundary. The piezoelectric constant (d33) and electromechanical coupling factor (kp) attain maximum values of d33=180 pCN-1 and kp=0.28 at x=0.06, corresponding to a relatively large remanent polarization of Pr=37.1 μCcm-2 and a relatively low coercive field of Ec=42.7 kVcm-1.

Microstructural evolution and mixed electronic-ionic conduction properties of perovskite-type La0.6Sr0.4Co0.8Fe0.2O3 ceramics were investigated in the sintering temperature range 1100-1250℃. The results confirm the crucial role of sintering temperature on microstructure and mixed conduction properties. The improvement of the mixed conduction properties with the increased sintering temperature from 1100℃ to 1200℃ is ascribed to the development of densification. Further increase of the sintering temperature above 1200℃ declined the mixed conduction properties due to the generation of excessive liquid. With respect to the mixed conduction properties, the preferred sintering temperature was ascertained to be 1200℃ for La0.6Sr0.4Co0.8Fe0.2O3 ceramics. The La0.6Sr0.4Co0.8Fe0.2O3 ceramic sintered at 1200℃ exhibited an electrical conductivity of 1.26×103 Ω-1cm-1 and an oxygen ionic conductivity of 3.73×10-2 Ω-1cm-1 at 800℃.

The structure, piezoelectric properties and ferroelectric properties of (Na0.5Bi0.5)1-xBaxTiO3 ceramics were investigated. A gradual change in crystalline structure and microstructure with the increase of BaTiO3 (BT) concentration was observed. It was ascertained that the rhombohedral-tetragonal morphotropic phase boundary (MPB) of the ceramics lies in the composition range of 0.04<x<0.08 at room temperature. The piezoelectric constant (d33) of the ceramics attains a maximum value of 155 pC/N at x=0.08. From the viewpoint of both piezoelectric constant and electromechanical coupling factor (kp), the composition of x=0.06 exhibits preferred piezoelectric properties. A dependence of piezoelectric properties on ferroelectric properties was detected for (Na0.5Bi0.5)1-xBaxTiO3 ceramics. It was found that both remanent polarization (Pr) and coercive field (Ec) contribute to the piezoelectric properties of the ceramics.