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



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


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.
Inorganic Chemistry


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


Li, J. , Smith, A. , Jiang, P. , Stalick, J. , Sleight, A. and Subramanian, M. (2015), True Composition and Structure of Hexagonal "YAlO<sub>3</sub>", Actually Y<sub>3</sub>Al<sub>3</sub>O<sub>8</sub>CO<sub>3</sub>, Inorganic Chemistry, [online], (Accessed July 12, 2024)


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Created February 1, 2015, Updated October 12, 2021