Effect of X on the transport properties of skutterudites LaFe₄X₁₂ (X = 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. - Highlights: • Thermoelectric properties of LaFe₄X₁₂ (X = P, As and Sb) were investigated. • LaFe₄As₁₂ show the highest electrical conductivity. • LaFe₄Sb₁₂ exhibit low electronic thermal conductivity between 50 and 600 K. • Above 650 K, LaFe₄P₁₂ compound show the lower electronic thermal conductivity. • LaFe₄Sb₁₂ compound show the highest Seebeck coefficient.