High-resolution neutron powder diffraction study on the phase transitions in BaPbO{sub 3}

Journal Article · Tue May 15 04:00:00 EDT 2007 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2007.03.009· OSTI ID:21015809

Visser, D ^[1]; Knight, K S ^[2]; IJdo, D J.W. ^[3]

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1. NWO-Physics, ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX (United Kingdom)
2. ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX (United Kingdom)
3. Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden (Netherlands)

Phase transitions that occurred in perovskite BaPbO{sub 3} have been investigated using high-resolution time-of-flight neutron powder diffraction. The structure at room temperature is orthorhombic (space group Imma), which is derived from the cubic aristotype by tilting the PbO{sub 6} octahedra around the two-fold axis (tilt system a {sup 0} b {sup -} b {sup -}). The orthorhombic structure shows anisotropic line broadening attributed to the presence of micro twins. At above about 573 K, BaPbO{sub 3} undergoes a discontinuous phase transition to a tetragonal structure (space group I4/mcm) with the tilting of the PbO{sub 6} octahedra being about the four-fold axis of the cubic aristotype (tilt system a {sup 0} a {sup 0} c {sup -}). With further increasing the temperature, BaPbO{sub 3} experiences a continuous phase transition to a simple cubic structure (space group Pm3-barm) at above about 673 K. The later phase transition is characterised by a critical exponent of {beta}=0.36, depicted by the three-dimensional Heisenberg universality class. The earlier reported Imma{sup {yields}}I2/m phase transition above room temperature has not been observed. - Graphical abstract: Temperature dependence of the octahedral tilting angles in BaPbO{sub 3}. The continuous line in tetragonal phase region is the fit to the expression: {phi}=A(T {sub c}-T) {sup {beta}} with the fitted values of T {sub c}=658(1) K, {beta}=0.36(2) and A=1.1(1). The shaded area indicates the possible two-phase region.

• OSTI ID: 21015809
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 5 Vol. 180; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ANISOTROPY
CUBIC LATTICES
LINE BROADENING
NEUTRON DIFFRACTION
ORTHORHOMBIC LATTICES
PEROVSKITE
PHASE TRANSFORMATIONS
SPACE GROUPS
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0273-0400 K
TEMPERATURE RANGE 0400-1000 K
TETRAGONAL LATTICES
TIME-OF-FLIGHT METHOD