Investigation of the thermal conductivity of sialon ceramics

SiAlON ceramics posses advantages of good mechanical and chemical properties andthey retain these properties also at high temperatures. However they have relatively lowthermal conductivity as a result of having complex crystal structure. Therefore SiAlONceramics are accepted as low thermal conductive materials and the parameters effecting theirthermal conduction mechanism are not previously studied in detail.The aim of this study is to investigate the thermal conductivity behaviour of SiAlONceramics which is crucial for many engineering applications. For this purpose, effects ofcompositional variation, grain boundary phase, microstructure, secondary phase addition andsolid solubility ratio are investigated. Compositional variation and the oxygen contaminationamount are found to be the most effective parameters as a result. Modeling studies carried outon a certain α-SiAlON composition revealed that, finite element analysis (FEM) resultsapplied on real microstructure image of the sample are in good agreement with theexperimental ones. This result is believed to be important for the thermal conductivityestimation of a SiAlON ceramic by means of the microstructural investigation or for thematerial design process for a required thermal conductivity value.Keywords: Thermal Conductivity, Thermal Diffusivity, Si3N4, SiAlON, Finite ElementAnalysisii