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Microstructural and Nonlinear Electrical Property of Prraseodymium Trioxide Ceramic

Author: PengShuJie
Tutor: WangYu
School: Southwest Jiaotong University
Course: Materials Science and Engineering
Keywords: Praseodymium oxide Varistor property Grain boundary potential barrier Oxygen vacancies Densification
CLC: TM282
Type: Master's thesis
Year: 2013
Downloads: 12
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Abstract


Pr6O11-based ceramics is a new type of varistor material, which was first detected by our research group. The pure Pr6O11ceramics can exhibit the nonlinear electrical properties at room temperature is the main characteristic of this ceramics in comparison with the conventional ZnO varistor. And the microstructure of this ceramics is simple. Previous work detected that the stability of the nonohmic property of Pr6O11-based ceramics was higher. And Pr6O11ceramics can exhibit an excellent property of the degradation resistance. The pure Pr6O11ceramics, consisting generally of one phase, is an advantage to explore the mechanism of the nonlinear electrical properties. The results of our research group showed that the poor sintering character and the low nonlinear coefficient will be the main limitation responsible for the application of this varistor ceramics in the protections of microeletronic circuits. Based on the quantities of the experimental data of our group, the properties of Pr6O11ceramics were improved through doping Sb. Al, Dy, Y and Er oxides, respectively. The aim of this manuscript is to study the influence of these oxides doping on the microstructure development, on the sintering character and on the nonlinear electrical properties.The results of experiment demonstrated that the addition of Sb oxide modified obviously the microstructure. the sintering character and the varistor properties of the Pr6O11ceramics. The doping of Sb2O3can promote the grain growth and the densification of Pr6O11ceramics. Therefore, it improves the sintering character of this ceramics. System densification was attributed to a mass transport mechanism, caused by the presence of Sb2O3, which could favour the oxygen vacancy apparition.The reaults of SEM and XRD demonstrated that the substitution of Pr by Sb in the system lattice of Pr6O11could create oxygen vacancies. The maximal values of the average grain size of Pr6O11is16.4μm by doping with1.0mol%. Highly dense ceramics were obtained, and the relative density reached the maximum value of96.8%by doping with2.0mol%. The microstructure of Pr6O11ceramics was influenced by the sintering temperature and the sintering time. The average grain size and the relative density of Pr6O11ceramics increased and then decreased as the sintering temperature increased. The average grain size and the relative density of Pr6O11ceramics increased as the sintering time increased. Work implied that the nonohmic property of Pr6O11-based ceramics was attributed to the Schottky barriers, which is associated with the enrichment oxygen adsorption at interface of grain boundary. Minor incorporation of Sb can create additional oxygen adsorption sites that increase the barrier height and improve the nonlinear characteristics. The nonlinear electrical properties of Pr6O11-based ceramics were improved though increasing sintering time, and the leakage current of this ceramics was decreased as increasing sintering time.The sintering temperatue has a significant influence on the microstructure and the relative density of Al2O3-doped Pr6O11ceramics. The dopants concentration of Al oxide modified obviously the microstructure and the relative density of Pr6O11ceramics sintered at 1150℃. Incorporation of Al element can create additional oxygen vacancies sintered at1150℃. The more creation of oxygen vancancies in Pr6O11ceramics can modify the lattice parameters, causing the change in the distance of the crystal face of Pr6O11and leading to the shift of the diffraction peak sites of Pr6O11to the left. The densification and the grain growth of the samples were attributed to a mass transport mechanism, caused by the presence of the more creation of oxygen vancancies. And the creation additional oxygen adsorption sites that increase the barrier height and improve the nonlinear characteristics of Pr6O11ceramics. The nonlinear electrical properties of Pr6O11-based ceramics were improved obviously doping Al element, and the leakage current was decreased sintered at1150℃.The varistor property of Pr6O11ceramics was improved through doping trivalent rare-earth oxides. Small Dy and Y oxide additives can enhance clearly the nonlinear characteristics of this ceramics; Incorporation of Er oxide can improve distinctly the varistor property of Pr6O11ceramics. One of Y2O3promotes the densification of the Pr6O11-based ceramics.

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CLC: > Industrial Technology > Electrotechnical > Electrical materials > Electric and ceramic materials > Piezoelectric ceramics
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