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Sr2FeMoO6 ceramics with different Fe/Mo antisite defect (ASD) concentrations and grain-boundary (GB) properties were prepared. The competitive and combining effects of GB and Fe/Mo ASD on the transport and magnetoresistance were discussed. The GB properties, that is, intergrain coupling strength, positively related with resistivity value, is extremely sensitive to the total flux of reducing gas, in general, lower total gas flux leads to larger resistivity, thus stronger intergrain coupling strength, and then the contributions of GB effect to low-field magnetoresistance (LFMR) increase appreciably regardless of the amount of ASD. In detail, when ASD concentration is less than 26%, LFMR is dominantly controlled by the GB effect. However, the suppressed ASD effect on LFMR behavior comes to play when the ASD content is larger than or equal to 26%, where the GB and ASD effects contribute together to the LFMR.

The microstructure, and dielectric and piezoelectric properties of the CeO2-modified potassium bismuth titanate K0.5Bi4.5Ti4O15 (KBT) piezoelectric ceramics were investigated. X-ray diffraction analysis revealed that the cerium-modified KBT ceramics have a pure four-layer Aurivillius-type structure. The piezoelectric properties of KBT ceramics were significantly enhanced and the dielectric loss decreased by cerium doping. The Curie temperature Tc and piezoelectric coefficient d33 for the KBT ceramics with 0.50 wt% cerium modification were found to be 550°C and 28 pC/N, respectively. The Curie temperature was found to decrease gradually from 555° to 541°C with cerium modification up to 1.00 wt%. Dielectric and annealing spectroscopy showed that the materials possess stable piezoelectric properties.

An Aurivillius phase bismuth layer-structured compound potassium bismuth titanate is synthesized using conventional solid-state processing. It was found that the range of sintering temperature for the potassium bismuth titanate is very narrow. Phase analysis was performed by X-ray diffraction, and microstructural morphology was assessed by scanning electron microscopy. The Curie temperature TC, piezoelectric coefficient d33, and mechanical quality factor Qm (kp mode) of the dense potassium bismuth titanate were found to be 555°C, 21.2 pC/N, and 1602, respectively. Dielectric spectroscopy showed that potassium bismuth titanate possesses stable high-temperature dielectric properties.

The effect on microstructure and electrical properties of (Co, Nb)-doped SnO2 varistors upon the addition of Pr2O3 was investigated by scanning electron microscopy and by determining I–V, ɛ–f, and R–f relations. The threshold electric field of the SnO2-based varistors increased significantly from 850 to 2280 V/mm, and the relative dielectric constants of the SnO2-based varistors decreased greatly from 784 to 280 as Pr2O3 concentration was increased up to 0.3 mol%. The significant decrease of the SnO2 grain size, from 4.50 to 1.76 μm with increasing Pr2O3 concentration over the range of 0–0.3 mol%, is the origin for the increase in the threshold voltage and decrease of the dielectric constants. The grain size reduction is attributed to the segregation of Pr2O3 at grain boundaries hindering the SnO2 grains from conglomerating into large particles. Varistors were found to have a superhigh threshold voltage and a comparatively large nonlinear coefficient α. For 0.15 mol% Pr2O3-doped sample, threshold electric field and nonlinear coefficient α were measured to be 1540 V/mm and 61, and for 0.3 mol% Pr2O3-doped sample, V and α were 2150 V/mm and 42, respectively. Superhigh threshold voltage and large nonlinear coefficient α qualify the Pr-doped SnO2 varistor as an excellent candidate for a high voltage protection system.