On the existence of a pyrochlore‐type phase in the system Bi₂O₃–TiO₂

The existence of a bismuth titanate in the range between Bi 2 Ti 4 O 11 (Bi 2 O 3 · 4 TiO 2 ) and Bi 4 Ti 3 O 12 (2 Bi 2 O 3 3TiO 2 ) has been investigated by X‐ray diffraction of samples prepared by solid state reactions. For reaction temperatures above 1100 °C and a starting composition Bi 2 O 3 · 2 TiO 2 there appeared additional lines which could be attributed to a cubic face‐centred cell with a = 10.354 Å. A multiphase Rietveld analysis based on X‐ray powder diffraction data confirmed the structural model of a pyrochlore for this compound. There is evidence that this phase belongs to the group of defect pyrochlores with a Bi 3+ ‐deficiency resulting in a composition of Bi 1.833 Ti 2 O 6.75 .