Thermoelectric properties of single crystalline Ba₈Al _xSi_46-x clathrate by using flux Czochralski method

Single crystalline Ba₈Al_xSi_46-x clathrates for use as thermoelectric materials were synthesized by the flux Czochralski method. Their aluminum content increased with that of the solution. The Seebeck coeffcients and electric specifc resistances of the Ba₈Al _xSi_46-x clathrates increased with aluminum content, whereas the carrier concentration decreased. The chemical compositions of the single crystalline samples from solutions of Ba₈Al ₃0Si₃0, Ba₈Al₄₀Si₃0 and Ba₈Al_50Si30 were Ba_7.8Al _14.1Si_31.9, and Ba_7.8Al_14.6Si _31.4, and Ba_7.8Al_14.9SiSi_31.1, respectively. The power factors of the single crystalline Ba _7.8Al_14.1Si_31.9, Ba_7.8Al _14.6Si_31.4 and Ba_7.8Al_14.9SiSi _31.1 at 773 K were 6.86×10^-4 7.75×10 ^-4 and 8.89×10^-4 V²/K²Ω m. The results indicate that the carrier concentration of the Ba ₈Al_xSi_46-x clathrates can be controlled by the composition of the solution, and that the flux Czochralski method is effective for synthesizing high performance thermoelectric materials.