title: Unusual transformation from strong negative to positive thermal expansion in PbTiO3-BiFeO3 perovskite.
abstract: Tetragonal PbTiO(3)-BiFeO(3) exhibits a strong negative thermal expansion in the PbTiO(3)-based ferroelectrics that consist of one branch in the family of negative thermal expansion materials. Its strong negative thermal expansion is much weakened, and then unusually transforms into positive thermal expansion as the particle size is slightly reduced. This transformation is a new phenomenon in the negative termal expansion materials. The detailed structure, temperature dependence of unit cell volume, and lattice dynamics of PbTiO(3)-BiFeO(3) samples were studied by means of high-energy synchrotron powder diffraction and Raman spectroscopy. Such unusual transformation from strong negative to positive thermal expansion is highly associated with ferroelectricity weakening. An interesting zero thermal expansion is achieved in a wide temperature range (30-500 °C) by adjusting particle size due to the negative-to-positive transformation character. The present study provides a useful method to control the negative thermal expansion not only for ferroelectrics but also for those functional materials such as magnetics and superconductors.
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.affiliation: Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China.
authors.forename: Longlong
authors.initials: L
authors.lastname: Fan
authors.affiliation: Argonne National Laboratory, X-Ray Science Division, Argonne, Illinois 60439, USA.
authors.forename: Yang
authors.initials: Y
authors.lastname: Ren
authors.affiliation: Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China.
authors.forename: Zhao
authors.initials: Z
authors.lastname: Pan
authors.affiliation: Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China.
authors.forename: Jinxia
authors.initials: J
authors.lastname: Deng
authors.affiliation: Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China.
authors.forename: Ranbo
authors.initials: R
authors.lastname: Yu
authors.affiliation: Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China and State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China.
authors.forename: Xianran
authors.initials: X
authors.lastname: Xing