10:45 AM - 11:00 AM
[R2-07] NMR study on Al local structures in Al-bearing CaTiO3 perovsskite
Keywords:Al-bearing CaTiO3 perovskite, Al local structures, NMR
The solid solution mechanism involving the substitution of trivalent cations for only Ti4+ occupying the B site in titanate perovskite has been studied in relation to electrical properties in materials science. This mechanism is important because it involves the formation of oxygen defects for charge compensation. On the other hand, the solid solution mechanism where Si4+ is replaced by Al3+ in MgSiO3 bridgemite is also attracting attention in deep earth science, as it may be related to elastic properties and water solubility.
In this study, we have investigated the solid solution formation of Al3+ in CaTiO3 perovskite. In previous JAMS annual meetings, we reported that the solid solution of Ca(Ti1-xAlx)O3-δ forms in the composition range of 0<x<0.25 under atmospheric pressure. The lattice volume decreases monotonically with the incorporation of Al3+, and a series of morphotropic structural changes from orthorhombic to tetragonal to cubic occur in the composition range of 0.21<x<0.25, which is close to the solid solution limit.
To obtain more information about the distribution of oxygen defects introduced into the structure, we performed 27Al-NMR measurements using the joint-use facilities of the Institute for Planetary Materials, Okayama University. This method is useful for understanding the local structure of Al. As a preliminary result, we have already reported that the local structure of Al is mainly VI coordinated, with some IV and V coordinated elements (Fig.1(b)). In this talk, we will discuss the local structure of Al in Al-bearing CaTiO3 perovskites in more detail, including the results of 2D-27Al-3QMAS-NMR measurements (Fig. 1(a)).
In this study, we have investigated the solid solution formation of Al3+ in CaTiO3 perovskite. In previous JAMS annual meetings, we reported that the solid solution of Ca(Ti1-xAlx)O3-δ forms in the composition range of 0<x<0.25 under atmospheric pressure. The lattice volume decreases monotonically with the incorporation of Al3+, and a series of morphotropic structural changes from orthorhombic to tetragonal to cubic occur in the composition range of 0.21<x<0.25, which is close to the solid solution limit.
To obtain more information about the distribution of oxygen defects introduced into the structure, we performed 27Al-NMR measurements using the joint-use facilities of the Institute for Planetary Materials, Okayama University. This method is useful for understanding the local structure of Al. As a preliminary result, we have already reported that the local structure of Al is mainly VI coordinated, with some IV and V coordinated elements (Fig.1(b)). In this talk, we will discuss the local structure of Al in Al-bearing CaTiO3 perovskites in more detail, including the results of 2D-27Al-3QMAS-NMR measurements (Fig. 1(a)).