| Zn O-based linear resistance ceramics are a new type of linear resistance, developed on the basis of Zn O varistors in the 1980 s. Zn O-based linear resistance ceramics have high using temperature, the small size and light weight, compared with the traditional metal resistance and carbon-based resistance, which meeting the electronic components development are featured by miniaturization with lightweight, short-length, and small size. Meanwhile, it possess exceptional nonlinearity in their current-voltage characteristics, a less fluctuation in resistivity, a smaller resistance temperature coefficient and the ability to absorb large amounts of energy, which prevent the current concentrate on one side of the resistor when a parallel connection was made. But, so far, its resistance repeatability and reliability did not meet the needs of industry, so we also need to further deepen the theory analysis of Zn O-based linear resistance ceramics to improve the electrical performances. In this paper, a better performance Zn O-Al2O3-Mg O system, in the reports, was selected as a basic system. Doping Ni O in the basic system, successfully prepared a new four components system. The sintering temperature was improved, and the effect of different contents of the rare-oxides and Fe2O3 added on the microstructure and electrical properties of Zn O-based linear resistance ceramics was investigated in details.First, the content of Ni O was added to the better performance Zn O-Al2O3-Mg O system, the effect of Ni O contents on the microstructure and electrical properties of Zn O-based linear resistance ceramics were investigated in detail. An optimum Ni O content was obtained in this paper, which was 15 mol%, so the best composition of the new four components system is 70 mol% Zn O-6 mol% Mg O-7 mol% Al2O3-15 mol% Ni O-0.5 mol% La2O3-1.5 mol% Si O2. The preparation process was improved, especially for the sintering temperature, the optimum sintering temperature was 1320 °C. Appropriate amount of Ni O can reduce the nonlinear property and improve the resistance temperature coefficient of the Zn O-based linear resistance ceramics, and the sintering temperature had great effects on the electrical properties of Zn O-based linear resistance ceramics. The samples with the Ni O concentration of 15 mol%, sintered at 1320 °C, possess the resistivity of 204.8 Ω·cm, the nonlinear coefficient of 1.18, the resistance temperature coefficient of 1.34 × 10-4/°C and the energy density reaches to the maximum of 809 J/cm3.Then, different doping amounts of rare-earth oxides had been added to the new four components system, sintered at 1320 °C. The effect of the different doping amounts of R2O3(R=La2O3、Y2O3、Sm2O3) on the microstructure and electrical properties of Zn O-based linear resistance ceramics were investigated in detail. The studies showed that the La2O3 addition on Zn O-based linear resistance ceramics has an obviously influence than the addition of Y2O3 and Sm2O3. The samples with the La2O3 content of 0.5 mol% exhibits excellent electrical properties with the resistivity of 253.5 Ω·cm and the resistance temperature coefficient of 1.7×10-4/°C, the nonlinear coefficient of 1.16 and the stability of-1.2 % in the variation rate of the resistivity for aging temperature.It is hardly to be avoided during the industrial production of Zn O-based linear resistance ceramics due to the usage of iron-made equipments. So, the Fe2O3 had been added to the the better performance Zn O-Al2O3-Mg O system, the effect of Fe2O3 contents on the microstructure and electrical properties of Zn O-based linear resistance ceramics were investigated in detail. The studies showed that Fe2O3 could improve the resistivity and lower the nonlinear coefficient, but the effect on the resistance temperature coefficient is disadvantageous. When the Fe2O3 content of 0.25 mol%, electrical properties of the samples with the resistivity of 458.4 Ω·cm, the nonlinear coefficient of 1.18 and the resistance temperature coefficient of-1.21×10-3/°C. |
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