Impact of Silica Additions on the Phase Composition and Electrical Transport Properties of Ruddlesden-Popper La2NiO4+δ Mixed Conducting Ceramics

The present work explores the possibility of incorporation of silicon into the crystal structure of Ruddlesden-Popper La2NiO4+δ mixed conducting ceramics with the aim to improve the chemical compatibility with lanthanum silicate-based solid electrolytes. Ceramics with the nominal composition La2Ni1−ySiyO4+δ (y = 0, 0.02 and 0.05) were prepared by the glycine nitrate combustion technique and sintered at 1450 °C. While minor changes in the lattice parameters of the tetragonal K2NiF4-type lattice may suggest incorporation of a small fraction of Si into the Ni sublattice, combined XRD and SEM/EDS studies indicate that this fraction is very limited (≪2 at.%, if any). Instead, additions of silica result in segregation of apatite-type La10−xSi6O26+δ and La2O3 secondary phases as confirmed experimentally and supported by the static lattice simulations. Both total electrical conductivity and oxygen-ionic transport in La2NiO4+δ ceramics are suppressed by silica additions. The preferential reactivity of silica with lanthanum oxide opens a possibility to improve the compatibility between lanthanum silicate-based solid electrolytes and La2NiO4+δ-based electrodes by appropriate surface modifications. The promising potential of this approach is supported by preliminary tests of electrodes infiltrated with lanthanum oxide.

Investigation on the Optical, Electrical and Dielectric Properties of La0.7Ca0.3MnO3 (LCMO) Via. Different Routes: A Comparative Analysis of Micro and Nanoparticles

In the proceeding way of material research in the field of manganites, LCMO micro and nanoparticles are synthesized via. the solid-state reaction route, glycine-nitrate combustion method respectively. The phase confirmation is done by XRD, FT-IR technique and the surface morphology viewed by Scanning Electron Microscope (SEM). The energy band gap obtained from Diffuse Reflectance Spectroscopy clearly suggests that the band gap of nanoparticles (2.06eV) is larger than that of the microparticles (1.58eV). Both samples comprise of wide band-gap semiconductor, so the refractive index is calculated using Herve and Vandamme relation. The impedance spectroscopy and dielectric properties of the two samples are studied from room temperature to 100oC over the frequency range 102-106 Hz. The Cole-Cole plot of impedance is fitted using the RC-Circuit R(QgRg)(QgbRgb)(CRin). The dielectric property is found to be enhanced in nanoparticles as compared to the microparticles. The findings suggest the nanoparticles be promising candidates in the field of high frequency devices as compared to micro.

Магнитные характеристики нанокомпозита на основе ферритов висмута

The magnetization processes of the BiFeO3 - Bi2Fe4O9 nanocomposite obtained by glycine nitrate combustion were studied. It was shown that the magnetic characteristics of the pure BiFeO3 and Bi2Fe4O9 compounds and the composite are significantly different. New properties of the synthesized substance are associated with the presence of exchange interaction at the interfaces.