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采用反向化学共沉淀法和高温煅烧法制备了磁铅石结构NdMgAl_(11)O_(19)粉体,并对粉体物相组成、化学成分、显微结构及晶格热膨胀行为进行了表征。结果表明:1 600℃煅烧得到的粉体为磁铅石结构NdMgAl_(11)O_(19),晶体发育良好,晶粒呈规则六方片状,各晶面光滑平整。a、c逐渐增大,与温度呈非线性关系。NdMgAl_(11)O_(19)的晶格热膨胀表现出各向异性,室温~1 300℃,a轴方向的平均热膨胀系数为7.3×10~(–6)/℃,c轴方向的平均热膨胀系数为11.2×10~(–6)/℃。Nd―O键的各向异性膨胀是晶格沿a、c轴方向表现出不同的热膨胀行为的主要原因。
NdMgAl_ (11) O_ (19) powder with magnetoplumbite structure was prepared by reverse chemical coprecipitation method and high temperature calcination method. The phase composition, chemical composition, microstructure and lattice thermal expansion behavior of the powder were characterized . The results show that the powder obtained by calcination at 1 600 ℃ is NdMgAl_ (11) O_ (19) with magnetoplumbite structure. The crystal is well developed and the grains are regular hexagonal flake with smooth and flat crystal planes. a, c gradually increased, showing a nonlinear relationship with temperature. The lattice thermal expansion of NdMgAl_ (11) O_ (19) shows anisotropy, the average coefficient of thermal expansion in the a-axis direction is 7.3 × 10 -6 / ° C at room temperature to 1,300 ° C, and the average coefficient of thermal expansion in the c-axis direction 11.2 × 10 -6 / ° C. The anisotropic expansion of the Nd-O bond is the main reason that the lattice exhibits different thermal expansion behaviors along the a and c axes.