A detailed structural study of selected compositions in the Bi3Nb1−xZrxO7−x/2 system using combined X-ray and neutron powder diffraction techniques was presented. Two distinct composition regions were evident. A limited pseudo-cubic solid solution range was observed up to about x = 0.4 and details of the defect structure were presented and compared with conductivity data. At higher Zr content, a polyphasic system was observed, with diffraction patterns dominated by a cubic δ-type phase. Evidence suggests that Zr was excluded from this phase and that the phase separation results in a bismuth rich δ-type phase characterised by a significantly larger unit cell parameter as well as high conductivity.

Defect Structure in Bi3Nb1−xZrxO7−x/2. I.Abrahams, F.Krok, W.Wrobel, A.Kozanecka-Szmigiel, S.C.M.Chan: Solid State Ionics, 2008, 179[1-6], 2-8