纳米氧化铪的制备与热膨胀性

Synthesis and Thermal Expansion in Nanosized Hafnium Oxide

制备了尺寸为4nm的HfO2纳米颗粒,并借助X射线原子对分布函数方法,研究了尺寸约4nm和体相HfO2颗粒的晶格热膨胀。结果表明,在纳米尺度的HfO2中,晶格沿a,c轴的热膨胀性增大,b轴热膨胀性稍微减小,体积热膨胀性增大。同时纳米HfO2晶格热膨胀的各向异性比体相大。该现象是由于尺寸效应导致结构畸变变大,尤其是次近邻Hf-O-Hf键角减小,随后升温过程中该畸变发生热弛豫趋向恢复至平衡位置导致的。

HfO2 nanoparticles with size of 4 nm were prepared through solvothermal process, and the lattice thermal expansion of nano and bulk HfO2 was studied by X-ray atom pair distribution function (PDF) method. The results showed that in nanoscale HfO2, the lattice thermal expansion along a and c axis increased, while b axis slightly decreased, and eventually volumetric thermal expansion increased. Meanwhile, the anisotropy of the thermal expansion of the nanosized HfO2 is larger than that of the bulk. The origin was that size effect induced a large structural distortion, mainly the reduction of the next nearest neighbor Hf-O-Hf bond angle, and then heating process triggered the relaxation of the distortion to equilibrium position.