  We have investigated the effect of Sb-deficiency on the thermoelectric figure
of merit (zT) of Zn4Sb3 prepared by solid state reaction route. At high
temperatures, the Seebeck coefficient (S) and electrical conductivity
({\sigma}) increase with increase in Sb deficiency whereas the thermal
conductivity (\k{appa}) decreases giving rise to an increase in the overall zT
value. The observations suggest that creation of vacancies could be an
effective route in improving the thermoelectric properties of Zn4Sb3 system.
This coupled to nanostructuring strategy could lead to the ultimate maximum
value of zT in this system for high temperature thermoelectric applications.
