INVESTIGADORES
LARREGOLA Sebastian Alberto
artículos
Título:
High-Temperature Behavior and Polymorphism in Novel Members of the Perovskite Family Pb2LnSbO6 (Ln = Ho, Er, Yb, Lu)
Autor/es:
SEBASTIAN ALBERTO LARREGOLA ; JOSE A. ALONSO; DENIS SHEPTYAKOV; MIGUEL ALGUERO; ANGEL MUÑOZ; VLADIMIR POMJAKUSHIN ; JOSE CARMELO PEDREGOSA
Revista:
INORGANIC CHEMISTRY
Editorial:
AMER CHEMICAL SOC
Referencias:
Lugar: Washington; Año: 2011 vol. 12 p. 5545 - 5557
ISSN:
0020-1669
Resumen:
The synthesis, crystal structure, and dielectric
properties of four novel members of the family of double perovskites Pb2LnSbO6 are described.
The roomtemperature crystal structures were refined from neutron powder diffraction
(NPD) data in the monoclinic C2/c (No. 15) space group. They contain a
completely ordered array of alternating LnO6 and SbO6 octahedra sharing corners, tilted in antiphase along the
three pseudocubic axes, with a a_b_b_ tilting scheme, which is very unusual in the crystallochemistry
of perovskites. The lead atoms occupy
highly asymmetric voids with 8-fold coordination due to the stereoactivity of
the Pb2þ electron
lone-pair. Several trends are observed for the entire family of compounds upon heating. The Ln = Lu, Yb, and
Er oxides display three successive phase transitions in a narrow temperature
range, as shown by differential scanning calorimetry (DSC) data, while the Ln
=Ho shows only two transitions. Different crystal structure evolutions have
been found from temperature-dependent NPD and DSC, following the space-group
sequence C2/cf P21/n R3fFm3mfor Ln = Lu and Yb, the sequence C2/c - P21/n ? R-3 ? Fm-3m
for Ln = Er, and C2/c ? P21/n ? Fm-3m for Ln = Ho. The Ln/Sb long-range
ordering is preserved across the consecutive phase transitions. Dielectric
permittivity measurements indicate the presence of a
paraelectric/antiferroelectric transition (associated with the last structural
transition), as suggested by the negative Curie temperature from the Curie Weiss
fit of the reciprocal permittivity.