Abstract
A detailed study of the sodium aluminate–carnegieite system (Na2−xAl2−xSixO4, 0≤x≤1) at temperatures between 800 and 1300°C has revealed five previously unreported phases. All of the new phases can be described as modulated variants of an underlyingβ-cristobalite parent structure. Atx≈0.05 theγ-NaAlO2-type structure (P41212,a=1/2ap,c=cp) (p=parent) is stabilized to room-temperature; atx≈0.2–0.45 an orthorhombic (Pbca,a=2ap,b=2bp,c=1/2cp) KGaO2-type structure is obtained, except atx≈0.35 where a new tetragonal (P41212,a=2ap,c=cp) phase is observed; atx≈0.5–0.6 a new cubic (P213,a=2ap) phase is obtained; atx≈0.7–0.9 a new orthorhombic (Pc21b,a=2ap,b=2bp,c=2cp) phase is obtained. XRD and electron diffraction data, refined unit cell dimensions, and the phase relationships at 1300°C are presented. The proposed space group symmetries are based on observed extinction conditions and constraints provided by a modulated structure description of the new phases. The materials are prepared by gel synthesis followed by solid state reaction in air.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
