Measurements of anisotropy, thermoelectric behaviour and multi-fractal aspects of FeSi and of complex custom made TE materials

Abstract

The understanding of the strongly directional properties of certain Thermoelectric materials needs further research on the subtle carrier and thermal electron paths that take place in complex natural and custom made materials. The way in which the material structure is built sometimes leads to strong anisotropy in basic properties such as the Seebek coefficient measured at a very small scale. A custom developed program Grau(2003) that calculates multifractal relationships using advanced image analysis aspects, was used at the same time as other techniques were used. The power relationships between the different concentration isolines Redondo et al.(1986) in a 2D section of the material perpendicular to the two orthogonal axes where the Voltage as a function of temperature were measured. and its variation with both range of scales and temperature may be used to explain the 30% differences measured in the Seebeck coefficients. The ratio between the surface separating subsets of different material properties and the volumes of the respective grains may be related to changes in fluxes that may be very different when measured at different scales in anisotropic and non-homogeneous materials (Linden and Redondo 2001). Basic topological and physical properties tare defined in a different way, when geometrical self similarity is apparent for a large range of scales studied in terms of box-counting fractal algorithms (Redondo 1990) and the relationship between some basic Thermo-electric Effects and geometry are studied.