Buy article online - an online subscription or single-article purchase is required to access this article.
research papers
Three crystalline forms (cubic, orthorhombic I and orthorhombic II) exist in the Na2O–Ca3Al2O6 solid-solution series at room temperature. A tetragonal form may be obtained by quenching. All the phases have lattices extremely close to the cubic form. The cubic and tetragonal varieties show no polymorphic transformations. The orthorhombic OI and OII phases become tetragonal at high temperature. There is complete agreement between the transition points revealed by X-ray diffraction and microscopy. However, only the order–disorder OII→T transition is observed by μDTA.