燃烧合成法制备ZrNiSn半哈斯勒热电材料

Combustion Synthesis of ZrNiSn Half-Heusler Thermoelectric Materials

利用燃烧合成法结合放电等离子烧结(SPS)技术在1 h内实现了ZrNiSn热电材料的制备,对样品的晶体结构、物相组成、微观结构以及热电性能进行了研究。晶体结构和物相分析结果表明,利用燃烧合成法制备了存在少量ZrNi_2Sn, Ni_3Sn_4等杂相的ZrNiSn合金材料。随着合金成分中Sn含量减少, Ni_3Sn_4相消失。微观结构分析结果显示,快速制备的ZrNiSn样品中的晶粒尺寸小于10μm,母相中会生成纳米晶粒和晶界,有利于增强声子散射。SPS处理后, ZrNiSn晶粒尺寸没有长大。热性能分析结果表明,随着温度的升高, ZrNiSn_(0.95)样品的热导率最小值为5.5 W·m^(-1)·K^(-1)。室温下, ZrNiSn样品的电导率最大为2.3×10~5 S·m^(-1),但由于对其Seebeck系数影响较大,因此制备的ZrNiSn基样品的功率因子没有显著提高。热电性能随着温度的增加而显著增加, 923 K时,利用燃烧合成法结合SPS技术制备的ZrNiSn_(0.95)样品的ZT值达到最大0.6。由于缩短了材料制备周期和降低了能源消耗,为高效、经济制备半哈斯勒热电材料提供了一种新的途径。

ZrNiSn thermoelectric materials were prepared within 1 h by combustion synthesis with conventional spark plasma sintering (SPS).The crystal structure,phase composition,microstructure and thermoelectric properties of samples were studied.The results of crystal structure and phase composition showed that a relatively high purity phase of ZrNiSn alloy was synthesized,however,a small amount of impurity phase ZrNi2 Sn and Ni3 Sn4 existed.Ni3 Sn4 phase was eliminated with the content of Sn decreasing.The results of microstructure observation showed that a grain size of ZrNiSn prepared by combustion synthesis was less than 10 μm,the nanoparticles and grain boundary were generated in the main phase,which was beneficial for enhancing the phonon scattering effect.After SPS, ZrNiSn grain size was inhibited.The results of thermal analysis indicated the minimum thermal conductivity of ZrNiSn0.95 sample was 5.5 W·m^-1·K^-1 with the increasing temperature.At room temperature,the maximum electrical conductivity of ZrNiSn sample was 2.3 × 10^5 S·m^-1 ,however,the power factor of ZiNiSn-based sample was not significantly improved due to its greater influence on the Seebeck coefficient.The thermoelectric properties increased significantly with the increase of temperature.A dimensionless thermoelectric figure of merit reached 0.6 at 923 K with ZrNiSn0.95 sample.It provided a new way for the efficient and economical preparation of half-Heusler thermoelectric materials because it shortened material preparation cycle and reduced energy consumption.