Crystal structure of Ln {sub 1/3}NbO{sub 3} (Ln=Nd, Pr) and phase transition in Nd{sub 1/3}NbO{sub 3}

The crystal structure of the A-site deficient perovskite Ln {sub 1/3}NbO{sub 3} (Ln=Nd, Pr) at room temperature has been determined, for the first time, as orthorhombic in space group Cmmm using high-resolution neutron powder diffraction. Pertinent features are the alternation of unoccupied layers o...

Full description

Saved in:
Bibliographic Details
Published in:Journal of solid state chemistry 2007-06, Vol.180 (6)
Main Authors: Zhang Zhaoming, Howard, Christopher J., Kennedy, Brendan J., Knight, Kevin S., Zhou Qingdi
Format: Article
Language:English
Subjects:
CATIONS
INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY
LATTICE PARAMETERS
LAYERS
NEODYMIUM COMPOUNDS
NEUTRON DIFFRACTION
NIOBIUM COMPOUNDS
ORTHORHOMBIC LATTICES
OXIDES
PEROVSKITE
PHASE TRANSFORMATIONS
PRASEODYMIUM COMPOUNDS
SPACE GROUPS
STRAINS
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0273-0400 K
TEMPERATURE RANGE 0400-1000 K
TETRAGONAL LATTICES
VACANCIES
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The crystal structure of the A-site deficient perovskite Ln {sub 1/3}NbO{sub 3} (Ln=Nd, Pr) at room temperature has been determined, for the first time, as orthorhombic in space group Cmmm using high-resolution neutron powder diffraction. Pertinent features are the alternation of unoccupied layers of A-sites and layers partly occupied by Ln cations, as well as out-of-phase tilting of the NbO{sub 6} octahedra around an axis perpendicular to the direction of the cation/vacancy ordering. The phase transition behaviour of Nd{sub 1/3}NbO{sub 3} has also been studied in situ. This compound undergoes a continuous phase transition at around 650 deg. C to a tetragonal structure in space group P4/mmm due to the disappearance of the octahedral tilting. The analysis of spontaneous strains shows that this phase transition is tricritical in nature. - Graphical abstract: Temperature dependence of the measured lattice parameters through the orthorhombic to tetragonal phase transition in the A-site deficient perovskite Nd{sub 1/3}NbO{sub 3}.
ISSN:0022-4596
1095-726X
DOI:10.1016/j.jssc.2007.03.029