Yansheng Gong

Synthetic process and spark plasma sintering of SrIrO 3 composite oxide

Single phase of SrIrO3 powders and ceramics were obtained by solid-state chemical reaction method and spark plasma sintering (SPS) technique, respectively. Phase evolutions, characteristics, morphology and resistivity of the samples were studied by using thermogravimetric analysis-differential scanning calorimetry (TG-DSC), X-ray diffractometry (XRD), field emission scanning electron microscopy (FESEM) and four-point probe method, respectively. The results showed that the reaction process to form SrIrO3 phase occurred between SrCO3 and IrO2 directly during the heating process. By using optimum fabrication conditions established from the TG-DSC results, single phase of SrIrO3 powders was synthesized at 800–1000 °C. SrIrO3 ceramics were sintered by SPS technique at 1000–1100 °C with a pressure of 30 MPa, showing a high relative density of 92%-96% and dense microstructure. The room-temperature resistivity of SrIrO3 ceramics was about 2×10−4 Ω·m. The present study can provide high-quality ceramic target for the preparation of SrIrO3 films in traditional physical vapor deposition (PVD) method.

Thermal Expansion and Electrical Characteristics of Ba(1−x)CaxTi0.92Zr0.08O3 Lead-Free Ceramics Prepared by a Modified Pechini Method

Ba(1−x)CaxTi0.92Zr0.08O3 (BTZ-xCa; x = 0–0.20) lead-free ceramics were prepared at a low temperature of 1210°C using as-synthesized nanoparticles through a modified Pechini method. The structure, permittivity, ferroelectricity, piezoelectricity, and thermal expansion characteristics of the ceramics that were influenced by varying calcium contents were studied in detail. X-ray powder diffraction and Raman results suggested that calcium could not induce the rhombohedral phase transition, and impurity phases were detected with excessive x. The electrical properties were basically elevated firstly in the room temperature direction of the temperature of phase transitions for orthorhombic-to-tetragonal with weaker internal stress, and then they apparently deteriorated with the shrunk octahedron size and strongly distorted structure with an increase of calcium content. The optimum electrical properties, i.e., d33, kp, and Qm of the BTZ-xCa ceramics were 261 pC/N, 24.9%, and 98 were obtained when the calcium content was 0.05, respectively. Additionally, the thermal expansion coefficient was studied for providing guidance on the ceramic materials production and usage.