Ni/(Ba,Sr)TiO_3复合正温度系数材料的电性能及镍的价态和分布(英文)

ELECTRICAL PROPERTIES AND NICKEL VALENCE STATES & DISTRIBUTION OF Ni/(Ba,Sr)TiO_3 POSITIVE TEMPERATURE COEFFICIENT COMPOSITE

在两种还原气氛中烧结制备低阻Ni/(Ba,Sr)TiO3复合正温度系数(positive temperature coefficient,PTC)材料,通过X射线光电子能谱仪研究复合材料表面镍的存在价态。结果显示:两种还原气氛中烧结后,大部分镍(Ni)都以单质存在,但是经600℃保温30 min热处理后,Ni主要以NiO存在。复合材料采用了Al2O3-SiO2-TiO2(AST)和PbO-B2O3-ZnO-SiO2玻璃烧结助剂。通过扫描电镜和元素分析得知:Ni颗粒在添加玻璃的陶瓷基质中分布得更均匀。对复合材料和石墨粉进行差示扫描量热-热重分析解释了上述现象。结合Ni颗粒的存在价态和分布研究了在两种还原气氛中烧结后复合材料的电性能。

The Ni/（Ba, Sr）TiO3 positive temperature coefficient （PTC） composite with low resistivity was sintered in two kinds of reducing atmospheres. X-ray photoelectron spectroscopy （XPS） was carried out to investigate the valence states of nickel on the composite surface. The results show that metallic nickel is the main chemical state after sintering in both atmospheres. However, NiO dominates after the composite is heat treated at 600 ℃ for 30 min. Al2O3-SiO2-TiO2 （AST） or PbO-B2O3-ZnO-SiO2 glass was used as sintering aids. Scanning electron microscope （SEM） and elemental mapping were carried out to analyze the nickel distribution in the ceramic matrix. Nickel particles are more homogeneously distributed in the glass-added ceramic matrix. To examine this phenomenon, differential scanning calorimetric （DSC） and thermogravimetric （TG） analyses of the composite and the graphite powder were conducted. Based on the valence states and distribution of nickel particles, the electrical properties of the composite were discussed.