Stabilisation and characterisation of a new βIII­phase in Zr­doped Bi2O3

Abstract

The solid state system Bi 2 O 3 :ZrO 2 has been investigated up to 28 mol% ZrO 2 using X-ray and neutron powder diffraction, ac impedance spectroscopy and differential thermal analysis. X-Ray powder diffraction has shown that a solid solution is formed with general composition Bi 22x Zr x O 3zx/2 (0.05¡x¡0.17) for samples calcined at 850 ‡C. Members of the solid solution adopt a new b-Bi 2 O 3 type structure termed b III , which is closely related to Pb 2 F 2 O. The defect structure of a sample of composition x~0.15 has been determined by combined high-resolution neutron and X-ray powder diffraction. High temperature powder X-ray diffraction has been used to confirm the structure of the high temperature polymorph, which is a cubic d-Bi 2 O 3 analogue. In the b III -phase, solid solution formation proceeds through an anion interstitial mechanism with respect to the hypothetical end member b III -Bi 2 O 3 , with interstitial oxide ions located in channels parallel to the c-axis. The defect structure involves a pair of Zr atoms coordinated to interstitial ions in the channels. A possible conduction mechanism is proposed. Differential thermal analysis and ac impedance measurements indicate a complex phase transition to a highly conducting polymorph (s 700 ~1.02 S cm 21 ) at temperatures above ca. 690 ‡C on heating. Crystal parameters: T~298 K, Bi 1.85 Zr 0.15 O 3.075 , M~449.49, tetragonal, P4 2 /nmc, a~7.7206(8), c~5.6370(6) A ˚, Z~4, U~336.0(1) A ˚3, D c ~8.889(3) g cm 23 ; T~1023 K, cubic, Fm3 ¯m, a~5.6277(4) A ˚, U~178.24(4) A ˚3, Z~2, D c ~8.379(2) g cm 23 .{Electronic supplementary information (ESI) available: crystal data, data collection and structural refinement data, atomic coordinates, isotropic thermal parameters, bond lengths, bond angles and contact distances for b III -Bi 1.85 Zr 0.15 O 3.075 at 298 K and for d-Bi 1.85 Zr 0.15 O 3.075 at 1023 K. See

Synthesis and characterization of Bi-doped zirconia for solid electrolyte

“…This type of variation may be due to transformation of m-Bi 2 O 3 to δ-and β III -Bi 2 O 3 because of oxygen deficiency [10]. This type of transition has been reported above 700°C due to δ-β III polymorphs of Bi 1.33 Zr 0.67 O 3-δ phase [8,9]. Interestingly, the present samples also show phase transition, which is lower than earlier reported values.…”

“…Abraham et al [9] has suggested that solid solution limit for Bi 2-x Zr x O 3+x/2 system is x=0.17. On the other hand, very few studies have been reported in literature on Bi-doped ZrO 2 system [11].…”

“…Due to stability and well-known conductivity of zirconia, several papers have been published on Bi-rich zirconia series [8][9][10]. Abraham et al [9] has suggested that solid solution limit for Bi 2-x Zr x O 3+x/2 system is x=0.17.…”

Specific Features of the Mixed Electronic-Ionic Conductivity of ZrO2/(Bi2CuO4 + xBi2O3) Composites

“…The solubility of ZrO 2 monotonically decreases with increasing temperature so that deficient fluorite phases are completely decomposed at 750°ë to form ZrO 2 phases and the Bi 1.84 Zr 0.16 O 3.08 solid solution with a β-Bi 2 O 3 structure [7]. Analogous results were obtained in [8], where the existence of a series of Bi 2 -x Zr x O 3 + x/2 solid solutions (0.05 ≤ x ≤ 0.17) with a deficient fluorite structure and a melting point at 860°ë was found. It is worth noting that no solid solutions were observed in the ZrO 2 -CuO system in the temperature range we studied [9].…”

Structural, thermal, and electrical properties of (100−x) ZrO2 (x) Bi2O3 compound

“…Since ZrO 2 exhibits good toughness and strength, the properties of ZrO 2 combined with the high conductivity of mBi 2 O 3 make it a superior oxygen ionic-conducting electrolyte [10]. In this system, the formations of various phases have been reported with changing processing condition [9,[11][12][13][14][15][16][17][18][19]. Recently, our group has also synthesized (100−x) ZrO 2 (x) Bi 2 O 3 (x05, 10, 15) system which showed good ionic conductivity [13].…”