采用机械合金化结合热压的方法,制备了纳米晶(Mg_(0.97)X_(0.03))_3Sb_2(X=Mg、Cr、Cu、Ti),进行了微结构表征和电阻率测量.结果表明其平均晶粒尺寸不超过40nm.(Mg_(0.96)X_(0.03))_3Sb_2晶体结构四面体位置的Mg-Sb结合距离变短,共价性增强.室温电阻从543Ωcm(Mg_3Sb_2)下降到137Ωcm((Mg_(0.97)Cr_(0.03))_3Sb_2)、121Ωcm((Mg_(0.97)Ti_0.03))_3Sb_2)、109Ωcm((Mg_(0.97)Cu0.03)_3Sb_2).替代样品的电阻在低温时为变程跳跃电导.电阻率的降低是由于替代形成的晶格中化学环境变化,原子间结合强度增加所致.
Mechanical alloying plus hot-pressing was employed to prepare nanocrystalline (Mg_(0.97) X_(0.03))_3Sb_2 (X = Mg, Cr, Cu, Ti)compounds which were characterized by mierostructural examinations and DC electrical resistance measurements. The results indicated that mean grain size of (Mg_(0.97) X_(0.03))_3Sb_2 compounds is smaller than 40nm. The distance between Mg-Sb of the tetrahedral positions decreases and the strength of covalent bond increases in the lattice of (Mg_(0.97) X_(0.03))_3Sb_2. It can be seen that the resistivity of nano-(Mg_(0.97) X_(0.03))_3 Sb_2 decreases from 543Ωcm (Mg_3Sb_2) to 137Ωcm ((Mg_(0.97) Cr_(0.03))_3Sb_2), 121Ωcm ((Mg_(0.97) Ti_0.03))_3 Sb_2)、109Ωcm((Mg_(0.97) Cu_(0.03))_3Sb_2)at 300K. Variable range hopping conduction happens at low temperature for the substituted samples. The decreasing of electrical resistivity is due to the changed chemical surrounding and the enhanced bond strength in the lattice of the substituted samples.
参考文献
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