title: The role of spontaneous polarization in the negative thermal expansion of tetragonal PbTiO3-based compounds.
abstract: PbTiO(3)-based compounds are well-known ferroelectrics that exhibit a negative thermal expansion more or less in the tetragonal phase. The mechanism of negative thermal expansion has been studied by high-temperature neutron powder diffraction performed on two representative compounds, 0.7PbTiO(3)-0.3BiFeO(3) and 0.7PbTiO(3)-0.3Bi(Zn(1/2)Ti(1/2))O(3), whose negative thermal expansion is contrarily enhanced and weakened, respectively. With increasing temperature up to the Curie temperature, the spontaneous polarization displacement of Pb/Bi (δz(Pb/Bi)) is weakened in 0.7PbTiO(3)-0.3BiFeO(3) but well-maintained in 0.7PbTiO(3)-0.3Bi(Zn(1/2)Ti(1/2))O(3). There is an apparent correlation between tetragonality (c/a) and spontaneous polarization. Direct experimental evidence indicates that the spontaneous polarization originating from Pb/Bi-O hybridization is strongly associated with the negative thermal expansion. This mechanism can be used as a guide for the future design of negative thermal expansion of phase-transforming oxides.
authors.affiliation: Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Chen
authors.forename: Krishna
authors.initials: K
authors.lastname: Nittala
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Forrester
authors.forename: Jacob L
authors.initials: JL
authors.lastname: Jones
authors.forename: Jinxia
authors.initials: J
authors.lastname: Deng
authors.forename: Ranbo
authors.initials: R
authors.lastname: Yu
authors.forename: Xianran
authors.initials: X
authors.lastname: Xing