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A series of CuMnMO (M = Mg, Al; x = 0-0.08) samples was prepared using the low-temperature hydrothermal method. Crednerite-type materials are obtained for a low level of substitution, i.e. up to x = 0.08, and transmission electron microscopy observations indicate that the average crystallite size decreases with an increase in x. The evolution of unit cell parameters in function of x, from Rietveld refinements using X-ray powder diffraction data, presents a distinct behaviour for both series, but corresponds in both cases to a regularisation of the triangular network in the ( a, b) plane. The investigation of the structural, thermal and magnetic properties reveals that the substitution has a significant role on the magnetism in CuMnMO (M = Mg, Al). It was found that the Mg and Al substitution on the Mn site leads to a small increase in the magnetisation values at low temperature, although the particle size decreases, which can be related to a release of magnetic frustration. [ABSTRACT FROM AUTHOR]

A fast and effective method for the preparation of NaTaO nanomaterials reported here is ultrasonic method with immersed sonotrode in the reaction medium followed by annealing at 600 °C. In order to remove the organic material and increase phase crystallinity, the materials were annealed at different temperatures (400, 600, 800 °C), for 6 h. The as-prepared samples were characterized by X-ray diffraction (XRD), thermal analysis (TG/DTG/HF), IR spectroscopy, surface area analysis (BET), and scanning electron microscopy (SEM/EDX). The structural characterization by X-ray powder diffraction revealed that heat-treated materials at 600 °C are well crystallized and the average size of the crystallites being approximately 60 nm, confirmed also by scanning electron microscopy. Thermal analysis has revealed five transformations process of NaTaO, the highest mass loss (10.67 %) taking place in the range 23-323.5 °C. It was found that the BET surface area decreases with temperature increasing which indicates a change in pores due to the removal of organics. From morphological analysis, it can be seen that particles have spherical shape and EDX revealed the purity of obtained materials. [ABSTRACT FROM AUTHOR]

This work describes the synthesis and characterization of copper doped sodium tantalate obtained by ultrasonically route with immersed sonotrode in the reaction medium followed by heat treatment at 600 °C, in air for 6 h. The as-obtained NaTaO:Cu material crystallizes in the orthorhombic structure with C m c 2(36) space group and the average size of crystallites was found to be 70 nm. Analysis by scanning electron microscopy with energy dispersive X-ray spectroscopy showed that the compound is chemically homogeneous and strongly agglomerated, and the value of the optical band gap E was 3.61 eV. Based on the complex impedance measurements, over the frequency range 50 Hz-2 MHz and different temperatures situated between 30 and 120 °C, the frequency and temperature dependence of the electrical conductivity of the sample was obtained. Activation energy for conduction E , was determined from measurements of dc-conductivity and increases linearly with the increases in temperature between 175 and 215 meV. [ABSTRACT FROM AUTHOR]

Combining functionalities in devices with high performances is a great challenge that rests on the discovery and optimization of materials. In this framework, layered oxides are attractive for numerous purposes, from energy conversion and storage to magnetic and electric properties. We demonstrate here the oxygen storage ability of ferroelectric LuFe2O4+x within a large x range (from 0 to 0.5) and its cycling possibility. The combination of thermogravimetric analyses, X-ray diffraction and transmission electron microscopy evidences a complex oxygen intercalation/de-intercalation process with several intermediate metastable states. This topotactic mechanism is mainly governed by nanoscale structures involving a shift of the cationic layers. The ferrite is highly promising because absorption begins at a low temperature (), occurs in a low oxygen pressure and the uptake of oxygen is reversible without altering the quality of the crystals. The storage/release of oxygen coupled to the transport and magnetic properties of LnFe2O4 opens the door to new tunable multifunctional applications. [ABSTRACT FROM AUTHOR]