True Composition and Structure of Hexagonal "YAlO3", Actually Y3Al3O8CO3

Published

February 2, 2015

Author(s)

Jun Li, Andrew E. Smith, Peng Jiang, Judith K. Stalick, Arthur W. Sleight, M. A. Subramanian

Abstract

The discovery of a brilliant blue color on introduction of Mn³⁺ into the trigonal bipyramidal (TBP)sites in YInO₃ has led to a search for other hosts for Mn³⁺ in TBP coordination. An obvious choice would be YAlO₃. This compound, which has only been prepared through a citrate precursor route, has long been considered isostructural with YInO₃. However, Mn³⁺ substituttions into YAlO₃ have failed to produce a product with the anticipated color. We find that the hexagonal structure for YAlO₃ with Al in TBP coordination proposed in 1963 cannot be correct based on its unit cell dimensions and bond valence sums. Our studies indicate instead that all, or nearly all, the Al in this compound has a coordination number (CN) of 6. On heating in air this compound transforms to YAiO₃ with the perovskite structure liberating CO₂. The compound long assumed to be a hexagonal form of YAlO₃ is actually an oxycarbonate with the ideal composition Y₃Al₃O₈CO₃. The structure of this compound has been characterized by neutron and X-ray powder diffraction data obtained as a function of temperature, by MASU27 Al NMR, by FTIR and by TEM. Refinement of neutron diffraction data indicates a composition of Y₃Al₃O₈CO₃. We find that the hexagonal structures of YGaO₃ and YfeO₃ from the citrate route are also stabilized by small amounts of carbonate. Surprisingly, Y₃Al₃O₈CO₃ forms a complete solid solution with YBO₃ having tetrahedral borate groups. Other unlikely solid solutions were prepared in the YAlO₃-YFeO₃, YAlO₃-YBO₃, YBO₃-YMnO₃, YBO₃-YFeO₃, and YBO₃-YGaO₃ systems.

Citation

Inorganic Chemistry

Volume

54

Issue

3

Pub Type

Journals

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Keywords

YAlO3, composition, structure, neutron, x-ray, carbonate

Citation

Li, J. , Smith, A. , Jiang, P. , Stalick, J. , Sleight, A. and Subramanian, M. (2015), True Composition and Structure of Hexagonal "YAlO₃", Actually Y₃Al₃O₈CO₃, Inorganic Chemistry, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=917069 (Accessed December 9, 2024)