Synthesis And Thermoelectric Properties Of Fe₂TiSn Heusler Alloy

A method combining vacuum arc melting with spark plasma sintering(SPS) technique was used to synthesize Fe2 TiSn, Fe2TiSn1-xSbx(x = 0, 0.1, 0.2, 0.3) and Fe2TiSn1-xSix(x = 0.05, 0.1, 0.2) Heusler alloys. Their crystal structures and thermoelectric properties were studied systematically. Main results of the present work are listed as following:(1) Fe2TiSn1-xSbx(x = 0, 0.1, 0.2, 0.3) and Fe2TiSn1-xSix(x = 0.05, 0.1, 0.2) samples were synthesized by the vacuum arc melting method using high purity Fe、Ti、Sn、Sb and Si. Analysis of XRD spectra indicates that all these samples contain small amounts of second phase, which is pure Sn.The samples of the vacuum arc melting reaction were processed by annealing and pickling(HCl concentration of 6%). Finally, single-phase bulk materials with high density were obtained using spark plasma sintering(SPS) of the powder samples.(2) It is found that the diffraction peaks of(400)、(331) and(420) in XRD patterns of Fe2TiSn1-xSbx(x = 0, 0.1, 0.2, 0.3) and Fe2TiSn1-xSix(x = 0.05, 0.1, 0.2) obviously moves shift high angle with increasing content of the Sb/Si. This indicates that Sb/Si atoms have successfully substitute Sn atoms and single-phase quaternary compounds is obtained.(3) With the TTO(thermal tansport option) module of physical property measurement system(PPMS), resistivity, thermal conductivity, Seebeck coefficient and the figure of merit ZT of Fe2TiSn1-xSbx(x = 0, 0.1, 0.2, 0.3) and Fe2TiSn0.9Si0.1 samples were measured simultaneously. The positive Seebeck coefficients of all these samples suggest that all these samples are p-type. The maximum seebeck coefficient α is about 311VK??, which is much smaller comparing to the result calculated by first-principles calculation.(4) The conductivities of Fe2TiSn1-xSbx(x = 0.1, 0.2, 0.3) and Fe2TiSn0.9Si0.1 have been significantly improved and the figure of merit ZT value have been increased, by Sb or Si-doping.