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ZnFe2O4/SnO2 semiconductor nanocomposites with various mole ratios were prepared by a simple chemical synthesis process that based on sol–gel method. The structural properties were determined by X-ray diffraction and scanning electron microscope technique. The XRD study reveals that no impurity phase, such as ZnO, Fe2O3, existed in all the samples. The average grain size was found to be about 39.51 nm when the mole ratio of ZnFe2O4/SnO2 is 2:1 (Z2S1), which is benefit for improving gas sensing property. The Z2S1 sample showed a relatively higher response (11.46) at a lower working temperature (176 °C) to acetone compared with other composites, and the response/recovery time were both very short. The improving gas sensing properties may be due to the fine grain and the formation of the ZnFe2O4/SnO2 heterojunction structure. [ABSTRACT FROM AUTHOR]

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Ni2+ and Zr4+ co-doped CaCu3Ti4O12 ceramics were successfully prepared by the sol-gel method. X-ray diffraction study reveals that single cubic perovskite CaCu3Ti4O12 phase was formed in all CaCu2.95Ni0.05Ti4−xZrxO12 samples. The SEM micrographs revealed that the microstructures change significantly with Ni2+/Zr4+ co-doping and sintering temperature while the average grain size grow up to 4.75 µm for CaCu2.95Ni0.05Ti3.9Zr0.1O12 sample sintered at 1100 °C for 8 h. Besides, all the samples show good nonlinear I-V electrical behavior. Further, the dielectric loss (tanδ) of CaCu2.95Ni0.05Ti3.9Zr0.1O12 sample shows the lowest value about 0.026 while the grain size reaches the maximum value. The dielectric constant (ε′) tends to be independent of temperature range from 20 to 180 °C when the measured frequency is above 20 kHz. These results indicate that Ni2+/Zr4+ co-doping can improve the dielectric and electrical properties of CaCu3Ti4O12. [ABSTRACT FROM AUTHOR]

(Li1+, Al3+) co-doped CaCu3Ti4O12 ceramics (CaCu3−2xLixAlxTi4O12, x = 0.05, 0.1, 0.15) were prepared by a sol-gel method and were sintered at 1020-1080 °C for 8 h to improve the geometric microstructure, dielectric and nonlinear I-V electrical properties. Notably, very high dielectric constant of 1 × 105 with good dielectric-frequency as well as dielectric-temperature stability can be achieved in CaCu2.8Li0.1Al0.1Ti4O12 ceramic sintered at 1060 °C. The average grain sizes, resistivity and the non-Ohmic properties are also improved compared to pure CaCu3Ti4O12. These results indicate that (Li1+, Al3+) co-doping at the Cu2+ site can improve the dielectric properties of CaCu3Ti4O12, supporting the internal barrier layer capacitance effect of Schottky barriers at grain boundaries. [ABSTRACT FROM AUTHOR]