Doroshenko H. The effect of concentration-induced electronic phase transitions on structure, galvanomagnetic, thermal and thermoelectric properties of bismuth-antimony solid solutions and their films

In the dissertation work the structure, mechanical, thermal, galvanomagnetic (GM) and thermoelectric (TE) properties of polycrystalline Bi1-xSbx alloys depending on the composition, temperature and magnetic field are studied. For the first time the deviation of the unit cell parameters from Vegard's law and a decrease in X-ray diffraction line widths at x ~ 0.01, 0.03 and 0.07 were observed, the anomalous peaks in the thermal conductivity and heat capacity isotherms were detected, the critical indices α for the heat capacity peaks were determined and the value α = 0.11 ± 0.01 was obtained, which is typical for a 2nd order temperature-induced phase transition (PT). The presence of the anomalies in the isotherms of thermoelectric and galvanomagnetic properties near the indicated compositions x was confirmed. The observed anomalies of properties are associated with the percolation PT from a dilute to a concentrated solid solution, PT into a gapless state and semimetal-semiconductor PT. The fact that the anomalies are found in the isotherms of different properties, determined both by electron and lattice subsystems of the crystal, suggests that the electronic PTs are accompanied by lattice restructuring processes, and indicates a strong electron-phonon interaction in Bi1-xSbx. Keywords: bismuth-antimony solid solutions, polycrystal, films, lattice constant, thermal conductivity, heat capacity, galvanomagnetic properties, thermoelectric properties, percolation, electronic phase transitions