Brewster angle of thermal diffusivity waves at an interface

•Determination of thermal diffusivity Brewster angle for diffusivity thermal waves.•Analysis of different combinations of interfaces to identify the Brewster angle.•Definition of a simple rule to know if an interface has thermal Brewster angle. In this work, we study the existence of the Brewster angle for thermal diffusivity waves. We analyze the propagation of plane thermal waves impinging upon an interface between two media. The condition of zero-reflection defines the Brewster angle. We demonstrate that the Brewster angle only exists for specific combinations of diffusivity and thermal conductivity of the incidence and transmission media.