CaO doped ZnO–Bi2O3 varistors: Grain growth mechanism, structure and electrical properties
| Autor: | Tata N. Rao, Raman S. Srinivasa, Ajit R. Kulkarni, K. Hembram |
|---|---|
| Rok vydání: | 2021 |
| Předmět: |
010302 applied physics
Materials science Process Chemistry and Technology Doping Sintering 02 engineering and technology Activation energy Atmospheric temperature range 021001 nanoscience & nanotechnology Microstructure 01 natural sciences Grain size Surfaces Coatings and Films Electronic Optical and Magnetic Materials Grain growth Chemical engineering 0103 physical sciences Materials Chemistry Ceramics and Composites Crystallite 0210 nano-technology |
| Zdroj: | Ceramics International. 47:1229-1237 |
| ISSN: | 0272-8842 |
| DOI: | 10.1016/j.ceramint.2020.08.242 |
| Popis: | In this study, the impact of CaO doping on the microstructure, phase and electrical properties of the ZnO–Bi2O3 system was studied. The powder was synthesized by the solution combustion route. Reduction in the crystallite size of ZnO from 23 nm to 17 nm of the powder sample with CaO doping was noted. Conventional sintering was used to consolidate the powders. Solid state reacted compositions revealed, from X-ray diffraction, formation of two phases (a) Ca4Bi6O13 at 750 °C and (b) Ca0.89Bi3.11O5.56 at 900 °C. An increase in density from 4.21 to 5.45 gcc−1 and a decrease in grain size from 4.50 to 1.54 μm with increasing CaO doping were also observed. A grain growth mechanism in the ZnO–Bi2O3–CaO system was proposed. The breakdown field increased up to 1 wt % CaO (27 kV cm−1) and after that decreased. Impedance spectroscopic investigation, in the temperature range of 100300 °C and frequency range of 0.1 Hz -1M Hz, exhibited two relaxations. These were attributed to defects formed. The two-stage activation energy of conductivity was noticed, which was similar to that observed in complex ZnO varistor systems. |
| Databáze: | OpenAIRE |
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