Pseudobrookite-based Ceramics with Low Thermal Conductivity Prepared from Fe-Ti-rich Heavy Mineral Sand Concentrate

The potential of using natural Fe-Ti-rich heavy mineral sand, as an abundant, inexpensive, and ecologically acceptable raw material for the processing of pseudobrookite-based ceramics for thermoelectric applications is presented. The as-received raw powder was used in untreated form or after pre-oxidation at 600°C, 700°C, and 800°C for 1h in an air. The starting powders were consolidated into dense compacts via conventional solid-state sintering or spark plasma sintering. The phase composition, ferrous:ferric ratio and microstructural characteristics of the powders and sintered compacts were investigated by XRD, Mössbauer spectroscopy and SEM. The samples with a higher fraction of pseudobrookite exhibit relatively low thermal conductivity ranging between 2 and 3 W m-1 K-1, which is promising for practical thermoelectric applications. The Seebeck coefficient depends on the ferrous:ferric ratio and is rather low, leading to low power factor values for all the samples which will have to be improved for practical applications.