Magnetic properties and NEXAFS-spectroscopy of Co-doped ferroelectric ceramic Bi5Nb3O15

Abstract

The majority of bismuth-containing compounds with a layered perovskite-like structure, analogues of the so-called Aurivillius phases, are of practical and theoretical interest owing to their ferroelectric properties. Bismuth niobate Bi 5 Nb 3 O 15 belongs to the group of mixed layered compounds. Its structure is characterized by the ordered alternation of fragments formed by one and two niobium-oxygen octahedra. Magnetic properties and NEXAFS of cobalt-containing solid solutions with a layered perovskite-like structure Bi 5 Nb 3−3x Co 3x O 15−δ have been studied. Solid solutions of Bi 5 Nb 3−3x Сo 3x O 15−δ (х ≤ 0.005) can be crystallized in tetragonal syngony (sp. gr. P4 / mmm), as cobalt content increases, monoclinic distortion of the unit cell emerges at 0.005 < х ≤ 0.04. The solid solutions as well as cobalt oxides СoO, Co 3 O 4 were studied by the NEXAFS spectroscopy. The analysis of the NEXAFS Co2p-spectra of cobalt-containing solid solutions and cobalt oxides revealed that the studied Co atoms were mainly in the +2 and +3 oxidation state. The isotherms of paramagnetic component of magnetic susceptibility of cobalt atoms in Bi 5 Nb 3−3x Co 3x O 15−δ are typical for antiferromagnets. The effective magnetic moments of single cobalt atoms calculated by extrapolating concentration dependencies of [χ para (Co)] to infinite dilution of the solid solutions exceed pure-spin values and increase as the temperature increases from 6.18 μB (90 K) to 6.69 μB (320 K). The formation of exchangebound aggregates of Сo(III) and Co(II) atoms predominantly with antiferromagnetic exchange types has been found in the solid solutions.

α-MnO2/FeCo-LDH on Nickel Foam as an Efficient Electrocatalyst for Water Oxidation

“… 22 The vibration of the NO 3 – group is observed at 1355 cm –1 . 23 The band at 661 cm –1 is related to Co–O vibrations, 24 and other bands including 745 and 1001 cm –1 are related to Fe–O vibrations ( Figure 1 c). 25 Figure 1 d shows the FTIR spectrum of α-MnO 2 nanoparticles.…”

NEXAFS–Spectra and Magnetic Susceptibility of Nickel and Chromium Doped of Bismuth Niobate

“…The chromium (nickel)-containing solid solutions [16,17] and is associated with formation of atomic defects in the structure. The X-ray patterns of the solid solutions were interpreted based on the space group P 2/m [16,17] To determine the charge state of chromium and nickel atoms, samples of solid solutions were examined using NEXAFS-spectroscopy using a BESSY-II synchrotron source. All NEXAFS spectra were recorded in total electron yield (TEY) mode.…”

Properties and Modification of Bismuth‐Layered Structure Ferroelectric Materials and Application in Sports

“…Lead-free dual-structure piezoelectric materials are widely used in the research of ferroelectric thin films and devices due to their fatigue resistance and high-temperature Curie characteristics [20]. However, due to the limitation of its own structure, it is difficult to effectively improve the two-level performance of ceramics, ferroelectric properties, and piezoelectric properties [21,22]. The physical and chemical properties of materials are determined by the structure of the material, and the structure of the material is related to the composition of the material.…”