원문정보
초록
영어
This paper presents the application of the bond valence method to estimate the valence charge distribution in several perovskite systems: La1xPbxMnO3 (x=0.1-0.5), La0.6Sr0. - xTixMnO3 (x=0.0-0.25) and La1xSrxCoO3 (x=0.1-0.5); the reviewing of their crystal structures is also incorporated. The results showed the failure of the elastic bonding mechanism in all studied systems and revealed the general deficit of the valence charge in their unit cells. This valence deficit was not associated with the structural defects and was not equally localized in all coordination spheres. As the content of substitution increased, the charge deficit declined systematically from balanced level, signifying the transfer of valence charge from the O6 to O12 spheres. This transfer depended on the valence deviation of spheres and the average reached near 2 electron per unit cell. The possible impact of the limitted accuracy of the available structural data on the bond valence results has also been considered.
목차
1. Introduction
2. Bond valence theory of perovskites
2.1. Perovskites in the 'pseudo-cubic' lattice
2.2. Calculation of BV for pseudo-cubic cell
3. The structural data
3.1. The pseudo-cubic lattices
3.2. Bond valence and non-stoichiometry
4. Failure of distortion theorem
4.1. The development of lattice constants
4.2. Test for the failure of distortion theorem in other perovskite systems
5. Valence charge distribution
5.1. Saturated bond length
5.2. Saturated bond valence
6. Problems and remarks
6.1. Resistibility to noise and accuracy of method
6.2. The charge non-stoichiometry versus the real non-stoichiometry x
6.3. Saturated bond valence and B4+ concentration
6.4. Remark on anisotropy of valence charge
7. Conclusion
Acknowledgement
References