Thermal expansion of disordered materials. Experimental study of the pyrocarbon family

Abstract

The authors first describe an experimental set-up which provides interlayer spacing X-ray measurements between 4K and 3000K. This set-up is essentially composed of a high-temperature furnace and a liquid helium cryostat; the diffractometer is connected to a computer. The thermal expansion of a series of lamellar materials with different crystalline structures was determined by the use of this apparatus. The analysis of the evolution of the coefficient of thermal expansion with respect to the degree of crystallinity shows, for the first time, some peculiar correlations between thermal and electronic properties.