Synthesis And Thermoelectric Properties Of ZrNiSn-Based Compounds By Solid State Reaction Method

In this thesis, a ternary alloy based of ZrNiSn was elected for study. DSC, XRD, and EDX analysis were adopted to explore the solid-state reaction processing parameters. The results showed that ZrNiSn-based compounds were synthesized at 1173K with holding for 96~168hrs, which were also under high purity Ar shielding. Any products were prepared without impurities.The SPS method was used to sintering the ZrNiSn-based compounds. The influence of different reaction temperature and holding time to density was discussed in detail. The results showed that material density reached 97.8% at 1123K with holding for 25 minutes.Hf and Sb were selected for substitution and doping for ZrNiSn. The result showed that the Hf-doped samples increased the Seebeck coefficient, and lowered the thermal conductivity, but has no great effect on electrical conductivity. The Sb-doped samples increased the electrical conductivity evidently, but also lowered the Seebeck coefficient. Therefore, the figure of merit of Hf-, Sb-doped ZrNiSn was greatly improved.The influence of the thermoelectric properties for ZrNiSn-based compounds with Pd-introduced was studied. Pd-substituted greatly lowered the lattice thermal conductivity, so as to the total thermal conductivity. But the Seebeck coefficient was reduced by Pd-substituted because of the interdict band width was reduced.The influence of the different substituted amount of Pd to based compounds was discussed. The result showed that the best thermoelectric properties appeared with 20 percent of Pd-introduced. The ZT-value reached 0.7 at 800k for the sample of. This was the best one reported of ZrNiSn system till now.