High-temperature behavior and polymorphism in novel members of the perovskite family Pb2LnSbO6 (Ln=Ho, Er, Yb, Lu).
Inorg Chem
; 50(12): 5545-57, 2011 Jun 20.
Article
em En
| MEDLINE
| ID: mdl-21618974
The synthesis, crystal structure, and dielectric properties of four novel members of the family of double perovskites Pb(2)LnSbO(6) are described. The room-temperature 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 LnO(6) and SbO(6) 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 Pb(2+) 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/c â P2(1)/n â R Ì
3 â Fm Ì
3m for Ln = Lu and Yb, the sequence C2/c â unknown â P2(1)/n â Fm Ì
3m for Ln = Er, and C2/c â P2(1)/n â Fm Ì
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.
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1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Oxigênio
/
Temperatura
/
Elementos da Série dos Lantanídeos
/
Chumbo
/
Antimônio
Idioma:
En
Revista:
Inorg Chem
Ano de publicação:
2011
Tipo de documento:
Article
País de afiliação:
Argentina
País de publicação:
Estados Unidos