Domain structure investigation of non-stoichiometric strontium ferrites and cobaltites

Abstract

Monte Carlo domain structure simulation and Debye equation calculation of XRD patterns were used to confirm the formation of domain structure and investigate its peculiarities. Correspondence of simulated XRD patterns with synchrotron powder diffraction experiments is achieved on the conditions that beside of 90o rotations of brownmillerite-like domains inside perovskite-like matrix each domain contains areas with perpendicularly oriented tetrahedral chains. Influence of such parameters as stoichiometry, average domain size, orthorhombic distortion degree on the XRD patterns is considered.

Nano-domain states of strontium ferrites SrFe1−MO2.5+ (M=V, Mo; y≤0.1; x≤0.2)

“…Doping of SrFe 1 À y M y O 2.5 þ x with high-charged cations leads to the formation of the system outside the homogeneity region of brownmillerite structure and gives rise to a nano-domain structure [7,8]. The "order-disorder" phase transitions in case of nanostructured oxides do not lead to destruction of the materials.…”

“…Many of other non-stoichiometric perovskite-like oxides ABO 3À δ have nano-domain structure for the values of oxygen stoichiometry 3À δ close to the vacancy-ordered brownmillerite phase's ABO 2.5 [8,[12][13][14][15][16][17]. Nano-domain structures appear as a result of phase separation into the vacancy-ordered phases and are the threedimensional intergrowth structures of nano-sized brownmillerite domains (perpendicularly oriented to each other) in a matrix of host perovskite lattice.…”

“…Nano-domain structures appear as a result of phase separation into the vacancy-ordered phases and are the threedimensional intergrowth structures of nano-sized brownmillerite domains (perpendicularly oriented to each other) in a matrix of host perovskite lattice. However, due to coherent jointing of differently rotated by 901 orthorhombic domains and regularity of cation sublattice in the system, the nano-domain structure appears in the X-ray diffraction patterns as narrow intense peaks of high-symmetric perovskite structure with weak broadened superstructural reflections [8].…”

“…Computer simulation of defective structures and their X-ray diffraction patterns [18] showed that, depending on the arrangement of the nano-domains and on the extended structural defects, the resulting diffraction effects have different features [8]. As a result of simulations, a systematic analysis of the influence of different types of disorder in strongly non-stoichiometric oxides on the diffraction patterns was performed [8].…”

“…As a result of simulations, a systematic analysis of the influence of different types of disorder in strongly non-stoichiometric oxides on the diffraction patterns was performed [8].…”