Stashko N. Synthesis, structure and physico-chemical properties of polycrystalline yttrium iron garnet

In dissertation using the complex of techniques of differential thermal analysis, infrared spectroscopy and X-ray structural analysis, the process of sol-gel synthesis of nanodispersed yttrium iron garnet. It has been found that pH of the solution of initial components, atmosphere and temperature of annealing influence on the process of obtaining garnet structure. Developed surface of initial oxide system obtained from the solution of pH=1 allowed to obtain high dispersed yttrium iron garnet at temperature of subsequent isothermal annealing 973 К under static air. It has been found that at isothermal annealing in the temperature range 973-1373 К mesoporous structure is formed, the pores with dimensions of 5 and 30 nm make the main contribution to the porous volume of which with the gradual disappearance of smaller pores with increasing annealing temperature. Sizes of blocks of coherent scattering of annealed samples vary in the range of 40-80 nm, and at 973 K of synthesis each particle is one block of coherent scattering, and at 1373 К particles contain several regions of coherent scattering. Magnetic microstructure of obtained yttrium iron garnet is characterized by non-equivalent positions of iron-ions in okta- and tetrasublattice of garnet due to oxygen defects. Saturation magnetization of the samples increases with increasing annealing temperature due to the increasing size of the particles and repair of surface defective layer. For the first time nanodispersed iron-yttrium garnet has been used as the cathode material of lithium power sources. Model of lithium power sources formed from garnet obtained at 973 К has specific capacity - 500 A·h/kg.