Evidence of the enhanced negative thermal expansion in (1 − x)PbTiO3-xBi(Zn2/3Ta1/3)O3

Abstract

A series of new solid solutions, (1 − x)PbTiO₃-xBi(Zn_2/3Ta_1/3)O₃ (0 < x < 0.2), have been synthesized, which show abnormally enhanced negative thermal expansion. The results of synchrotron X-ray diffraction reveal that with the increase in the dopant of Bi(Zn_2/3Ta_1/3)O₃ in the PbTiO₃ system, the increase in spontaneous polarization displacement could improve the negative thermal expansion behavior due to the spontaneous volume ferroelectrostriction (SVFS) effect. The STEM images show that PbTiO₃-Bi(Zn_2/3Ta_1/3)O₃ exhibits stronger polarization than PbTiO₃, which reveals a greater deviation. Moreover, the STEM images show that the element Ta has larger spontaneous polarization displacement than other B-site atoms. Furthermore, density functional theory calculations confirm the enhancement of hybridization between the A-site cations and oxygen upon the introduction of Bi(Zn_2/3Ta_1/3)O₃. All the above pieces of evidence indicate that the interplay between the cations and oxygen plays a key role in the enhancement of negative thermal expansion.