Theory of thermal conduction in thin ceramic films

The theory of heat conduction in ceramics by phonons! and at high temperatu re es also by infrared radiation, is reviewed. The phonon mean ii-re path i s limited by three-phonon interactions and by scattering of various imperfe ctions. Point defects scatter high-frequency phonons: extended imperfection s, such as inclusions, pores, and grain boundaries, affect mainly low-frequ ency phonons. Thermal radiation is also scattered by imperfections. but of a larger size, such as splat boundaries and large ports. Porosity also redu ces the effective index of refraction. For films there are also external bo undaries, cracks, and splat boundaries, depending on the mettled of deposit ion. Examples discussed are cubic zirconia, titanium oxide, and uranium oxi de. Graphite and graphene sheets, with two-dimensional phonon gas, ale disc ussed briefly.