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

Abstract

The existence of a bismuth titanate in the range between Bi2Ti4O11 (Bi2O3 · 4 TiO2) and Bi4Ti3O12 (2 Bi2O3 3TiO2) has been investigated by X‐ray diffraction of samples prepared by solid state reactions. For reaction temperatures above 1100 °C and a starting composition Bi2O3 · 2 TiO2 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 Bi3+‐deficiency resulting in a composition of Bi1.833Ti2O6.75.

Phase relations in the Bi2O3-TiO2 system

“…2), and also the peritectic nature of the pyrochlore melting Bi 2 Ti 2 O 7 → L + Bi 2 Ti 4 O 11 . Our results agree with the known data on the decomposi tion of pyrochlore above 600°C [8,[31][32][33], i.e., indi cate its metastability within the temperature range from room temperature to 1000°C, and also with the data on the formation of Bi 2 Ti 2 O 7 by solid phase syn thesis above 1000°C [34][35][36][37].…”

Sol–gel synthesis, structure characterization and Raman spectroscopy of Gd2−2xBi2xTi2O7 solid solutions

“…This material presents a visible light absorption in the region 420-500 nm [13]. Preparation of Bi 2 Ti 2 O 7 was completed by various synthetic processes like: conventional solid-state approach [14], metalorganic chemical vapor deposition [15], co-precipitation route [16], etc. This oxide is not a stable phase in the Bi 2 O 3 /TiO 2 phase diagram, so it is difficult to form pure bismuth titanate composition Bi 2 Ti 2 O 7 [3].…”

Synthesis, X-ray diffraction investigations and spectroscopic analysis of yttrium-substituted pyrochlore oxides Y2−2xBi2xTi2O7 via a sol–gel process

“…Bismuth titanate pyrochlore exhibits a visible light absorption in the region 420-500 nm [4]. Synthesis of Bi 2 Ti 2 O 7 was performed by various synthetic routes like: conventional solidstate approach [5], metalorganic chemical vapor deposition [6] sol-gel processing [7] co-precipitation route [8], etc. However, it is difficult to form pure bismuth titanate composition.…”