Low-temperature thermoelectric properties of α- and β-Zn4Sb3 bulk crystals prepared by a gradient freeze method and a spark plasma sintering method

The low temperature thermoelectric properties of Zn4Sb3 samples prepared by the gradient freeze (GF) method and sintering have been characterized. With decreasing temperature a dramatic rise in the thermal expansion is observed associated with the structural transition from beta- to alpha-phase; DeltaIII = 2.8 X 10(-4) at T-s(GF) = 257.4 K for GF and DeltaIII = 1.6 X 10(-4) at T-s(S) = 236.5 K for sintered samples. Enhancement is observed in electrical conductivity and p-type thermopower at T-s(GF) and T-s(S), while a reduction is observed in the magnetic susceptibility. The GF sample exhibits higher thermoelectric performance than the sintered sample. The power factor of the a-phase in the GF sample is twice as large as that of the beta-phase; it exceeds 20 muW/cm.K-2 between 120 and 240 K, indicating that the alpha-phase Zn4Sb3 is one of the prime candidates for thermoelectric materials for cryogenic use. (C) 2002 Elsevier Science B.V. All rights reserved.