Characterization of SiCN Ceramic Material Dielectric Properties at High Temperatures for Harsh Environment Sensing Applications

A novel method is presented in this paper to precisely characterize the dielectric properties of silicon carbon nitride (SiCN) ceramic materials at high temperatures for wireless passive sensing applications. This technique is based on a high quality factor (Q) dielectrically loaded cavity resonator, which allows for accurate characterization of both dielectric constant and loss tangent. The dielectric properties of SiCN ceramics are characterized from 25 degrees C to 1000 degrees C. Two different metallization processes are implemented for the measurements with the highest temperatures of 500 degrees C and 1000 degrees C, respectively. A custom-made thru-reflect-line calibration kit is used to maximize the measurement accuracy at every temperature point. It is observed that the dielectric constant and loss tangent of the SiCN sample without Boron doping increase from 3.707 to 3.883 and from 0.0038 to 0.0213, respectively, when the temperature is raised from 25 degrees C to 500 degrees C, and for the SiCN with Boron doping (SiBCN), the dielectric constant and loss tangent increase from 4.817 to 5.132 and from 0.0020 to 0.0186, respectively, corresponding to the temperature ranging from 25 degrees C to 1000 degrees C. Experimental uncertainties for extracted epsilon r and tan delta are no more than 0.0004 and 0.0001, respectively. The temperature dependency of Si(B)CN dielectric properties, as well as the dielectrically loaded cavity resonator structure, provides the basis for the development of wireless passive temperature sensors for high-temperature applications.