Structure Analysis of the 6H - Ba[Ti,Fe3+,Fe4+]O3-δ^ Solid Solution

Published

February 1, 1998

Author(s)

I E. Grey, C Li, L M. Cranswick, Robert S. Roth, Terrell A. Vanderah

Abstract

The 6H form of BaTiO₃ forms an extensive solid solution with barium iron oxide, having the general formula BaTi_1-X-yFe³⁺_xFe⁴⁺_yO_{3-δ, δ=x/2, where the Fe}u3+^/Fe⁴⁺ ratio depends on reaction temperature and gas atmosphere. Solid solution members having iron predominantly as Fe³⁺ or as Fe⁴⁺ were prepared by quenching from high temperatures in air or slow cooling to 200 degrees Celsius} in oxygen respectively. The structural variations in both series were obtained from Reitveld refinements of powder X-ray diffraction data. For the series with yO, the progressive substitution of Ti⁴⁺ by Fe³⁺ is accompanied by the formation of O[1] oxygen vacancies in the h-BaO₃ layers which separate pairs of occupied face-shared octahedra. The maximum vacancy concentration occurs at x=0.67, corresponding to a composition of Ba O2 in the h-stacked layers, and to a change from face-shared octahedra to pairs of edge-shared square pyramids. Solid solution members with x>0.67 were unstable relative to other polymorphs. Further incorporation of iron into the 6H structure at high temperature occurs by substitution of Ti⁴⁺ by Fe⁴⁺, ie by increasing y. The observed structural variations in the solid solution phases are explained in terms of the Ba and M atom packing and the changes in interatomic interactions between the metal atoms as oxygen is removed from the O[1] site.

Citation

Journal of Solid State Chemistry

Volume

135

Issue

2

Pub Type

Journals

Keywords

barium iron titanium oxides, BaTiO3, hexagonal barium titanate, Rietveld refinement, solid solution

Citation

Grey, I. , Li, C. , Cranswick, L. , Roth, R. and Vanderah, T. (1998), Structure Analysis of the 6H - Ba[Ti,Fe³⁺,Fe⁴⁺]O₃-δ^ Solid Solution, Journal of Solid State Chemistry (Accessed July 18, 2024)