Z. A. Mikhaylovskaya

Bi13-xMexMo5O34±δ (Me = Mg, Ca, Sr, Ba) solid solutions: synthesis and properties

A series of complex oxides Bi13-xMexMo5O34±δ, Me = Mg, Ca, Sr, Ba were synthesized and studied. The solid solutions ranges and polymorphic modifications limits were determined. High temperature X-ray powder diffraction measurements showed the deviation of unit cell parameters dependence versus temperature from the linear function. Processes of forming of ceramic samples based on the synthesized powders were analyzed, and dense ceramic samples were obtained. Impedance spectroscopy displayed the changes of slope of Arrhenius plots which correspond with the HT-XPRD measurements. The presence of two different forms of monoclinic modification was supposed. The studied materials are promising ionic conductors, with the highest conductivity values about 6u2009×u200910−3xa0Sxa0cm−1 at 973xa0K and 1.4u2009×u200910−4xa0Sxa0cm−1 at 623xa0K.

Mn-doped Bi26Mo10O69-d: synthesis and characterization

In this work, we research two series of Mn-substituted bismuth molybdates: Bi26-2xMn2xMo10O69-d and Bi26Mo10-2yMn2yO69-d. The synthesis of powder samples is performed by the conventional solid state technology. Samples are characterized by X-ray diffraction, scanning electron microscopy, and chemical analysis methods, and it is shown that single phase Bi26-2xMn2xMo10O69-d and Bi26Mo10-2yMn2yO69-d complex oxides form up to xxa0=xa00.8 and yxa0=xa00. We use densitometry, grain size measurements and scanning electron microscopy to study the morphology of ceramic pellets and powders. This issue reveals formation of dense ceramic samples with low porosity (≤3%). High-temperature X-ray diffraction is used to define small deviation of unit cell parameters from their linear dependence on temperature. Measurement of electrical conductivity is made using a.c. impedance spectroscopy method. We observe the decrease of electrical conductivity in Bi26-2xMn2xMo10O69-d series depending on dopant concentration.

Substituted bismuth vanadates and chromates: New aspects

The work is devoted to the synthesis and attestation of a number of substituted vanadates and chromates of bismuth. For bismuth vanadates of the BIMEVOX family, the homogeneity regions of the Bi4V2 – xCrxO11 ± d solid solutions have been refined, the features of the structure change of the compounds with increasing chromium content and changing temperature have been noted, and the powders and ceramics have been studied by electron microscopy. For the first time, as an impurity, an individually substituted bismuth chromate of the composition Substituted bismuth chromate of the Bi13Cr5 – yVyO34.5 – d (y = 0.95 ± 0.05) composition has been detected for the first time as an impurity and synthesized as an individual compound, which has been characterized by X-ray diffraction, electron microscopy, chemical analysis, and photoelectron spectroscopy data; its homogeneity range has been determined, and electroconductive characteristics have been studied.

Structure and conductivity in iron-doped Bi 26 Mo 10 O 69-δ

A series of complex oxides of general formula Bi26Mo10-2xFe2xO69-3x was synthesized and studied. The solid solution formation ranges and polymorphic modification limits were determined. SEM investigations and chemical analysis showed homogenous samples and confirmed the theoretical concentrations of the dopant. High-resolution neutron and X-ray diffraction were used to describe the structural features of the solid solution at ambient and high temperatures (30–800xa0°C). Structure refinement was carried out by Rietveld analysis using a combination of X-ray and backscattered neutron data. Close inspection of the fit at room temperature revealed a non-centrosymmeric P1 space group and additional peaks associated with oxygen and/or magnetic ordering. Magnetic measurements showed the samples had low magnetic susceptibility and a magnetic transition at ~u2009−u200920xa0°C. A.C. impedance spectroscopy was used to determine the electroconductive properties of Bi26Mo10-2xFe2xO69-3x. Two basic types of impedance curves were detected at low and high temperatures, correlated with a change from triclinic to monoclinic symmetry. Details of both the monoclinic and triclinic structures are discussed, with the variation of electroconductive properties explained by structural changes.

One-dimensional oxygen-ion conductors based on phosphorus-substituted bismuth molybdates: Preparation and characterization

Our study deals with the preparation, characterization, and electric conduction properties of complex oxides of formula Bi13Mo5–xPxO34.5–d, which manifest oxygen-ion conductivity at medium-range temperatures.

New complex-oxide materials Bi 25.6 Ba 0.4 Mo 10–2 y Me″ 2 y O 69– d : Synthesis and characteristics

An integrated study was carried out of complex-oxide materials based substituted bismuth molybdate Bi26Mo10O69, which exhibit such potentially valuable characteristics as oxygen-ion conductivity at medium temperatures and catalytic activity. Compounds with formula Bi25.6Ba0.4Mo10–2yMe 2yO69–d were synthesized by the standard ceramic technology and characterized by the methods of X-ray phase analysis, scanning electron microscopy, and laser light scattering. The morphological characteristics of the ceramic based on Bi25.6Ba0.4Mo10–2yMe 2yO69–d were examined; the catalytic characteristics of granulated powders were studied for the example of ethylene oxidation; the method of impedance spectroscopy was employed to examine the temperature dependence of the electrical conductivity of the samples; it was shown that the conductivity of Bi25.6Ba0.4Mo10–2yMe 2yO69–d exceeds that of the matrix composition.