Microstructure-electrical conductivity relationship of Si(Ni)BCN ceramics

Wireless passive sensors based on surface acoustic wave (SAW) provide a good solution for the measurement demand under high temperature and harsh conditions. SiBCN ceramics have excellent mechanical properties at high temperature and semiconductor behavior, making them potential for electrode of SAW sensors. To achieve the target conductivity, a series of SiBCN and SiNiBCN coatings are prepared by polymer derived ceramics (PDC) method and the influence of microstructure on the conductivity of the coatings is discussed. The results show that the conductivity of the SiBCN coatings is affected by both the content of free carbon and the degree of graphitization. The introduction of Ni leads to the formation of Ni₂Si conductive microcrystals at lower temperatures and catalyzes the graphitization of the carbon phase, so that the SiNiBCN coatings show lower electrical resistivity. The amount of the metal conductive phase and the graphitization degree of the carbon phase increase with the pyrolysis temperature, resulting in decrease of the SiNiBCN coatings resistivity.