Polymorphism and properties of Bi2WO6 doped with pentavalent antimony

• The limit of Bi2W1−xSbxO6−y solid solutions is at x = 0.05.
• Bi2W1−xSbxO6−y does not fully transform into high-temperature monoclinic phase.
• Sb5+ has a weak effect on the temperatures of the ferroelectric transitions.
• γ→γ‴γ→γ‴ transition near 650 °C was observed as strong permittivity peak at 0.01–8 Hz.
• The conductivity of Bi2W0.96Sb0.04O6−y at 800 °C reaches 0.02 S/cm.

Antimony-containing solid solutions isostructural with bismuth tungstate, Bi2WO6, have been prepared in air as polycrystalline samples by solid-state reactions and as single crystals by unseeded flux growth. The antimony in the solid solutions is in a pentavalent state and substitutes for tungsten in the structure of Bi2WO6. The Bi2W1−xSbxO6−y solid solutions have been shown to exist in the composition range 0 ⩽ x ⩽ 0.05. We have examined the effect of Sb5+ doping on the polymorphism and properties of Bi2WO6. In contrast to undoped Bi2WO6, antimony-substituted bismuth tungstate does not completely transform into its high-temperature, monoclinic phase at 960 °C and remains two-phase up to temperatures approaching its melting point. Antimony substitution for tungsten has a weak effect on the temperatures of the ferroelectric phase transitions. Heterovalent substitution of Sb5+ for W6+ is accompanied by the formation of extra oxygen vacancies and an increase in the electrical conductivity of the solid solutions by one to two orders of magnitude relative to undoped Bi2WO6.

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