S.A. Petrova

Oxygen-ionic conductors based on substituted bismuth molybdates with column-type structural fragments

The possibility of synthesizing oxygen-ionic conductors from substituted bismuth molybdates containing [Bi12O14]n8n+ columns, MoO4 tetrahedra, and isolated Bi ions in their structure was studied. The specifics of their structure and electric conductivity were investigated. The general formula of the solid solutions can be recorded as Bi13Mo5 − xMexO34 − δ, where Me is the fouror five-valent d metal (Ti, Zr, V, Nb). The electric conductivity of doped bismuth molybdates considerably increased compared with that of the matrix compound. The electric conductivity reached 5.5 × 10−3 S cm−1 at 700°C and 1.8 × 10−4 S cm−1 at 350°C for the zirconium-doped compound with x = 0.4. The porosity of the ceramics was less than 5%; the thermal expansion coefficient was of the order of 14 × 10−6 K−1. Based on the set of their characteristics, these compounds are recommended as materials for membranes of electrochemical devices.

Structural and thermal stability of BIMEVOX oxygen semiconductors

The results on the structural and thermal stability of different modifications of solid solutions Bi4V2 − xFexO11 − δ (BIFEVOX), where x = 0.05–0.6, and Bi4V2 − xCux/2Tix/2O11 − δ (BICUTIVOX), where x = 0.025–0.50, are shown. The stability is assessed by varying the thermodynamic parameters of the medium and also the time parameters with the use of modern methods, namely, the high-temperature X-ray diffraction analysis, the differential scanning calorimetry, and the dilatometry. The γ-modification of BIFEVOX is shown to be stable in a wide range of temperatures and oxygen partial pressures.

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.