Dipartimento di Scienze Chimiche e Geologiche, and INSTM, Università di Cagliari, S.S. 554, Bivio per Sestu, 09042 Monserrato (CA), Italy.
J Chem Phys. 2013 Feb 7;138(5):054702. doi: 10.1063/1.4789479.
The structural properties of zinc ferrite nanoparticles with spinel structure dispersed in a highly porous SiO(2) aerogel matrix were compared with a bulk zinc ferrite sample. In particular, the details of the cation distribution between the octahedral (B) and tetrahedral (A) sites of the spinel structure were determined using X-ray absorption spectroscopy. The analysis of both the X-ray absorption near edge structure and the extended X-ray absorption fine structure indicates that the degree of inversion of the zinc ferrite spinel structures varies with particle size. In particular, in the bulk microcrystalline sample, Zn(2+) ions are at the tetrahedral sites and trivalent Fe(3+) ions occupy octahedral sites (normal spinel). When particle size decreases, Zn(2+) ions are transferred to octahedral sites and the degree of inversion is found to increase as the nanoparticle size decreases. This is the first time that a variation of the degree of inversion with particle size is observed in ferrite nanoparticles grown within an aerogel matrix.
具有尖晶石结构的纳米氧化锌铁颗粒在高度多孔的 SiO(2)气凝胶基质中的结构性质与块状氧化锌铁样品进行了比较。特别地，使用 X 射线吸收光谱确定了尖晶石结构中八面体 (B) 和四面体 (A) 位之间的阳离子分布细节。X 射线吸收近边结构和扩展 X 射线吸收精细结构的分析表明，锌铁尖晶石结构的反演程度随粒径而变化。特别是在微结晶的块状样品中，Zn(2+)离子占据四面体位置，三价 Fe(3+)离子占据八面体位置（正常尖晶石）。当粒径减小时，Zn(2+)离子迁移到八面体位置，并且随着纳米颗粒尺寸的减小，反演程度增加。这是首次在气凝胶基质中生长的铁氧体纳米颗粒中观察到反演程度随粒径的变化。
