Enhanced Thermoelectric Properties of Bi2O2Se Ceramics by Bi Deficiencies

Polycrystalline Bi 2− x O 2 Se ceramics were synthesized by spark plasma sintering process. Their thermoelectric properties were evaluated from 300 to 773 K. All the samples are layered structure with a tetragonal phase. The introduction of Bi deficiencies will cause the orientation alignment and change of effective mass. As a result, a significant enhancement of thermoelectric performance was achieved. The maximum of Seebeck coefficient is −568.8 μV/K for Bi 1.9 O 2 Se at 773 K, much larger than −445.6 μV/K for pristine Bi 2 O 2 Se. Featured with very low thermal conductivity [~0.6 W·(m·K) −1 ] and an optimized electrical conductivity, ZT at 773 K is significantly increased from 0.05 for pristine Bi 2 O 2 Se to 0.12 for Bi 1.9 O 2 Se by introducing Bi deficiencies, which makes it a promising candidate for medium temperature thermoelectric applications.