Research in thermoelectrics has been intensively carried out in recent years, partly motivated by global energy and environmental management. Material improvement is essential for further development and a wider utilization of thermoelectrics. This PhD thesis focuses on the thermoelectric material ZnSb, which has among its advantages of high abundance, low toxicity and low cost compared to other thermoelectric materials. This three-year PhD work was built upon an understanding of semiconductor transport, and the investigation of thermoelectric properties of ZnSb has led to a deeper knowledge of thermoelectrics. The experiments have been designed for improving the thermoelectric transport properties and new knowledge and insight have been acquired. Manuscript I Impurity band conduction in the thermoelectric material ZnSb