Structure and conductivity in tungsten doped δ-Bi<inf>3</inf>YO<inf>6</inf>
61 - 67
Solid State Ionics
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© 2017Solid solution formation in the system Bi3Y1 − xWxO6 + 3x/2 has been studied using a combination of X-ray and neutron powder diffraction and a.c. impedance spectroscopy. Compositions in the solid solution adopt the δ-Bi2O3 type structure, with single phases evident from x = 0.00 to x = 0.20. Evidence for dopant clustering is presented and discussed. Models for the defect structure derived from diffraction studies are presented. Tungsten is proposed to adopt a tetrahedral coordination geometry, with a distorted octahedral geometry adopted by yttrium. Calculated coordination numbers for bismuth of around five are consistent with stereochemical activity of the Bi 6s2 lone pairs of electrons. Despite a significant lowering of the nominal vacancy concentration with respect to δ-Bi3YO6, as well as enhanced vacancy trapping by W6+, tungsten doping is found to have very little influence on the total conductivity of δ-Bi3YO6. This is attributed to the compensating effect of enhanced oxide ion mobility caused by lattice expansion.
AuthorsBorowska-Centkowska, A; Leszczynska, M; Wrobel, W; Malys, M; Krynski, M; Hull, S; Krok, F; Abrahams, I
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