SYNTHESIS, STRUCTURE AND GRAIN STRUCTURE OF THE SOLID SOLUTIONS BASED ON (1-x)BiFeO3-xYMnO3(x=0,40-0,50)

The materials based on the (1-x)BiFeO3-xYMnO3(x=0.40, 0.45, 0.50) system of two classical multiferroics were prepared under various conditions of solid-phase synthesis. In total, four methods are distinguished, differing in temperatures and times of synthesis. The crystal structure of the obtained objects was studied using the methods of X-ray diffraction and phase analysis. It is shown that the materials have a complex multiphase and almost always morphotropic composition, in which perovskite phases with different unit cell distortions coexist. It was noted that the formation of a monoclinic phase cannot be ruled out during the synthesis process. A ferrimagnet type phase of the YFeMnO5 is almost always formed at the synthesis temperatures above 900 °C, while a mullite type phase of the Bi2Fe4O9 is formed at lower temperatures. The grain structure of the prepared ceramics cross-section surface areas was studied. The analysis of the formation of the microstructure in various synthesis methods showed that at sintering temperatures above 900 °C the surface morphology is a set of crystallites of different fractions, having the shape of hexagonal and rectangular prisms. At sintering temperatures below 900 °C, the presence of the effect of “enveloping” grains with submicron-sized particles was noted. This effect may be related to magnetic properties, but requires additional research. An X-ray spectral analysis of the elemental composition of the cross-sectioned areas was carried out. It is shown that, regardless of the shape of the crystallites, their energy spectra contain characteristic lines of all five components of the studied system. This may indicate the formation of a mixture of solid solutions.

bismuth ferrite, yttrium manganese, multiferroics, solid state solutions, microstructure, grain structure