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Microstructure, Properties and Kinetic Characterization in SnO2-Based Varistor with Addition of CuO Nano Particle

Mahmoudi, Pezhman | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 49343 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Nemati, Ali; Seyyed Reyhani, Morteza
  7. Abstract:
  8. The aim of this study is to investigate the effect of Copper oxide on the microstructure, properties, and grain growth kinetic in Tin oxide- Based varistors. Copper oxide was mixed in Tin oxide with different concentration, including 0, 0.1, 0.25, 0.5, and 1 mol% and the samples were sintered at 1250, 1300, and 1350 oC. Then, phase and microstructural characterization was investigated and consequently, electrical properties were evaluated. According to results, Copper Oxide with forming the liquid phase through the sintering process, accelerated grain growth. It was found that, by increasing concentration of CuO, mean grain size was increased from 2.6 µm in 1250 oC and 5 hours to 17.1 µm in 1350 oC and 5 hours. This grain size increase, decreases electrical field from 3.25 kV/cm to 0.64 kV/cm. On the other hand, the kinetic of grain growth in the compounds, with 0, 0.1, 0.25, and 0.5 mol% CuO were investigated. It was observed that the growth exponent in the sample without CuO, is 2 and this parameter gradually increased to 4.5 with the addition of CuO till 0.5 mol%. Furthermore, the activation energy of grain growth decreased from 597.4 kj/mol to 364.9 kj/mol. The change in growth exponent indicates the change in grain growth mechanism. Due to the decrease in the activation energy of grain growth, it can be concluded that the mechanism of grain growth was changed from diffusion in the solid state to diffusion in the liquid state
  9. Keywords:
  10. Copper Oxide ; Grain Growth ; Sintering ; Tin Oxide-Based Varistors ; Grain Growth Kinetics

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