Preparation and electrical properties of Ni/(Ba,Sr)TiO3 PTC composite with low resistivity |
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Authors: | Xiaoyan Li Yuanfang Qu Jing Gao |
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Affiliation: | (1) Key Laboratory for Advanced Ceramics and Machining Technology of Ministry of Education, Tianjin University, Tianjin, 300072, China;(2) AMI DODUCO (Tianjin) Electrical Contacts Manufacturing Co., Ltd, Tianjin, 300111, China |
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Abstract: | Ni/ (Ba,Sr)TiO3 PTC composite of low resistivity was fabricated by a solid state route. A mildly reducing sintering atmosphere was employed to avoid the oxidation of nickel. Metallic nickel is the main chemical state after sintering in the mildly reducing sintering atmosphere. With the increase in nickel amount, the room-temperature resistivity declines and the PTC effect worsens. The quantum mechanical tunneling effect at the Ni–(Ba,Sr)TiO3 interface is presumably the prime factor in the deterioration of the PTC effect. PbO–B2O3–ZnO–SiO2 glass was added to modify the interface between nickel and (Ba,Sr)TiO3 ceramics. The intergranular phase introduced by the glass has an amorphous structure and exists at the interfaces and triple junctions of (Ba,Sr)TiO3 grains and nickel grains. No obvious diffusion occurs at the interface between crystalline (Ba,Sr)TiO3 grain and the intergranular phase. Also the added-glass improves the distribution of metal phase. The proper glass addition screens interfacial electron tunneling effect and improves the composite electrical properties. An abundance of the intergranular phase due to excess glass will, however, result in high room-temperature resistivity. The influences of nickel amount and glass amount on the microstructure evolution and electrical properties were analyzed. |
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Keywords: | (Ba,Sr)TiO3 PTC (positive temperature coefficient) composite Ni (nickel) Electrical properties |
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