Stability and range of the type II Bi 1−x W x O 1.5+1.5x solid solution

Abstract

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Synthesis and Properties of Vanadium Substituted Bismuth Tungstates with Fluorite-like Structure

“…As the radius of vanadium ions is smaller than that of tungsten ions (r(Bi 3+ ) = 0.60 Å; r(W 6+ ) = 0.60 Å; r(V 5+ ) = 0.54 Å [9]), one can observe slight contraction of unit cell volume of the substituted compounds. The same tendency is found for the samples with increasing tungsten content and is reported in [6,7]. On the whole, all experimental data which are obtained in the present work for matrix compounds are in a good agreement with previous results [6,7].…”

“…The same tendency is found for the samples with increasing tungsten content and is reported in [6,7]. On the whole, all experimental data which are obtained in the present work for matrix compounds are in a good agreement with previous results [6,7].…”

“…2). This peak can be related to the presence of the phase transition from cubic to tetragonal structure [6,7]. TEC value of the Bi 23 W 4 O 46.5 equals to 13·10 -6 °C -1 and is close to that for lanthanum manganite cathode materials.…”

“…This compound melts congruently at 1040 °C and has reversible phase transition at 900 °C. So, as it was shown by Wind [6,7] [6,7]. In case of low cooling rate, a phase transition from cubic to tetragonal structure occurs at 700 °C.…”

Oxygen Dynamics in Transition Metal-Doped Bismuth Oxides

“…The Bragg peaks observed at lower temperature (150−600 °C) are superstructure peaks due to type II-like ordering within the oxygen sublattice and thus confirm the presence of type II Bi-W-O within that temperature range. In agreement with our recent in situ NPD study,16 a decomposition and phase transition to the thermodynamically stable combination of type Ib + Aurivillius phases is observed at around 750 °C. At 950 °C, the sample transforms back to single-phase type II.The significant decrease in intensity of the superstructure peaks (which almost disappear within the two broad diffuse peaks, see Figure2b) is a clear indication of an increase in oxygen disorder in the sample compared to the quenched lowtemperature type II phase.…”