New, intermediate polymorph of CeAlO<subscript>3</subscript> with hexagonal structure – formation and thermal stability.

This work presents the results of studies on solid state reaction in a highly dispersed CeO 2 –Al 2 O 3 system under a reducing atmosphere. The formation of a new metastable hexagonal form of CeAlO 3 , isomorphous to hexagonal YAlO 3 , at 850 °C has been confirmed for the first time by TEM, XRD, FT-IR and measurement of magnetic susceptibility. Above 900 °C, the hexagonal phase transformed into a common tetragonal polymorph. Magnetic susceptibility data indicates that both CeAlO 3 polymorphs contain Ce 3+ ions, but the unit cell volume per formula unit is noticeably bigger (26%) for the hexagonal polymorph. This may suggest that the hexagonal CeAlO 3 polymorph is stabilized by the interaction with the Al 2 O 3 support. [ABSTRACT FROM AUTHOR]

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