Ask for a reprint
email :
* Give your email
2018
ACL
|
W.Cao, X.Yang, F.Lu, L.Liu, X.Kuang, M.Allix, '8H-10H Stacking Periodicity Control in Twinned Hexagonal Perovskite Dielectrics', Inorg. Chem. 57 4117 (2018) doi:10.1021/acs.inorgchem.8b00296
Isovalent substitution of Zr4+ for smaller Ti4+ was performed in the 8-layer twinned hexagonal
perovskite (referred to as 8H) tantalate Ba8Ti3Ta4O24, which stabilizes a 10-layer twinned hexagonal
perovskite (referred to as 10H). The formation of the 10H phase can occur at low substitution
concentration (x = 0.1) in Ba8ZrxTi3-xTa4O24 at 1300 °C, and reverts back to the 8H phase upon
heating at elevated temperatures. Such a 10H-to-8H phase transformation is suppressed at the
higher Zr-substitution contents (x > 0.1). The 10H Ba8Zr0.4Ti2.6Ta4O24 (x = 0.4) composition adopts
a simply P63/mmc disordered structure with the Zr cations preferably located in corner-sharing
octahedral (CSO) sites compared to face-sharing octahedral (FSO) sites. This 8H-10H phase
competition dependent on the substitution of Zr4+ for Ti4+ and firing temperature is discussed in
terms of the FSO B-B repulsion controlled by the cationic size, as well as the stacking periodicity
that affects the thermodynamic stability. Both 8H and 10H pellets of Ba8ZrxTi3-xTa4O24 exhibit
comparable and poorer microwave dielectric properties than the parent 8H Ba8Ti3Ta4O24, which is
characterized by cationic disorder and FSO B-B repulsion. The 8H and 10H Ba8ZrxTi3-xTa4O24
ceramics display electrical insulator behavior but with electrically heterogeneous microstructure on
the bulk grains. This study demonstrates the opportunity to control the stacking periodicity for
twinned hexagonal perovskite via tuning the B-cationic size and the firing temperature.
|
|