NATURAL PYRITE OF N- AND P-TYPE CONDUCTIVITY AS A PROMISING NATURAL MATERIAL FOR THE CREATION OF CONVERTERS OF THERMAL ENERGY INTO ELECTRICAL

Abstract

The search for semiconductors that allowed to provide thermoelectric efficiency is under way. There is an increased interest in the study of thermoelectric (thermoelectric EMF) properties of natural pyrite. The object of the study is natural pyrite of n- and p-type conductivity. Thermoelectric properties of pyrite are the subject of the study. The purpose of the study is to reveal regularities of changes in the thermoelectric properties of natural pyrite depending on temperature. To reach this purpose the following problems should be solved: to collect the equipment for temperature dependences of voltage U(T) and resistivity ρ(T) of natural pyrite in the range 300...600 K; to determine temperature dependences of voltage U(T), fixed between two different points on the surface of natural pyrite samples in the range 300...600 K; to determine temperature dependences of resistivity ρ(T) of natural pyrite samples in the range 300...600 K; to analyze obtained results in terms of theoretical and applied research. The results of the study of thermoelectric properties of natural pyrite FeS2 n- and p-type conductivity, as well as natural pyrite with quartz inclusions are presented. This study is due to the need to search for and study new compositions, on the basis of which economical, cheap thermo generators can be manufactured. Experimentally, temperature dependencies of resistivity and voltage fixed between two points on the surface of the samples were obtained. For this purpose, samples fixed between two contacts in a specially prepared cell were placed in a muffle furnace that ensures uniform heating. For improving uniform heating as inside as surface layers of the experimental samples the special metal cube, which has function of the electrostatic protector in addition, has been used. It is special actually from a point of view raising quality of the measuring. Samples with quartz inclusions have been found to exhibit steeper voltage rises with increasing temperature than samples of hole and electron pyrite. It has been proved that the maximum values of the voltage recorded between two points on the surface of the samples are 2.5104μV for pyrite with quartz inclusions, 1.4104μV for hole pyrite and do not exceed 7103μV for electron pyrite. The maximum resistivity values are 15 Ωmm for hole pyrite, 432.75 Ωmm for electron pyrite and 1 kΩm∙m for pyrite with quartz inclusions. Based on the data obtained, the authors conclude that hole pyrite from a practical point of view is the most promising material for using in thermoelectric materials science. The physical mechanisms of the observed effects are discussed