Effect of X on the transport properties of skutterudites LaFe4X12 (XÂ =Â P, As and Sb) compounds

We have investigated the influence of substituting P by As and As by Sb on the thermoelectric properties of LaFe4X12 (X = P, As and Sb) compounds. It has been found that substituting P → As → Sb show significant influence on the bands dispersions, bond lengths, effective masses, the carriers mobility and hence the transport properties. Replacing P by As cause significant increases in the carriers concentration with increasing the temperatures, while replacing As by Sb exhibit insignificant increase in the carriers concentration of LaFe4Sb12 with respect to LaFe4As12. It is clear that LaFe4As12 show the highest electrical conductivity among the other compounds along the temperature range. Calculations show that LaFe4Sb12 exhibit low electronic thermal conductivity in the temperature range between 50 and 600 K, then above 650 K the LaFe4P12 compound show the lower electronic thermal conductivity. The Seebeck coefficient of LaFe4X12 (X = P, As and Sb) compounds increases with increasing the temperature. Moving from P → As → Sb cause significant increases in the Seebeck coefficient and LaFe4Sb12 compound exhibit the highest Seebeck coefficient along whole temperature scale. The power factor of LaFe4X12 (X = P, As and Sb) compounds increases with increasing the temperature and LaFe4Sb12 compound show the highest power factor along the whole temperature range.