Silicon Carbide (SiC) is a wide bandgap semiconductor with highly appreciated properties making it ideal for high power, high frequency, and high temperature applications. One of these properties is the high thermal conductivity (λ) which is mentioned in almost every single publication, yet very few measurements of λ on SiC have been made and essentially no knowledge has been accumulated on the limiting factors on λ or on what role λ plays in a finished device. Improvement of λ may be achieved if the material is isotope enriched i.e. the SiC is dominatingly 28Si12C. In this paper we will highlight the properties of SiC as a power device material with specific emphasis on λ. The results from 28Si12C show that the layers are very low doped and have an isotope purity of 99% or better.