Structure and thermal expansion of the tungsten bronze Pb2KNb5O15

Lin, Kun and Wu, Hui and Wang, Fangfang and Rong, Yangchun and Chen, Jun and Deng, Jinxia and Yu, Ranbo and Fang, Liang and Huang, Qingzhen and Xing, Xianran (2014) Structure and thermal expansion of the tungsten bronze Pb2KNb5O15. Dalton Transactions, 43 (19). pp. 7037-7043. ISSN 1477-9226

Abstract

The structure and thermal expansion behavior of the tetragonal tungsten bronze oxide Pb2KNb5O15 were investigated by neutron powder diffraction and high-temperature X-ray diffraction. Below the Curie temperature, TC (orthorhombic phase, TC ≈ 460°C), the cell parameters a and c increase with temperature, while b decreases. The thermal expansion coefficients are αa = 1.29 × 10-5°C-1, αb = -1.56 × 10-5°C-1, and αc = 1.62 × 10-5°C-1. Temperature-dependent second harmonic generation (SHG), dielectric, and polarization-electrical field (P-E) hysteresis loop measurements were performed to study the symmetry and electric properties. We show that the distortion and cooperative rotation of NbO6 octahedrons are directly responsible for the negative thermal expansion coefficient along the polar b axis. It is suggested that Pb-O covalency, especially in the large and asymmetric pentagonal prisms, may be related to orthorhombic distortion and abnormal spontaneous polarization along the b axis. This study shows that tungsten bronze families are possible candidates for exploring negative thermal expansion materials.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Published version cannot be displayed due to copyright restrictions.
Faculty / Department / School: No Faculty
Date Deposited: 18 Sep 2017 01:16
Last Modified: 20 Sep 2017 00:48
Uncontrolled Keywords: high temperature X-ray diffraction; hysteresis loop measurements; negative thermal expansion coefficients; negative thermal expansion material; spontaneous polarizations; tetragonal tungsten bronze; thermal expansion behavior; thermal expansion coefficients; strength of building materials; mechanical properties; lead and alloys; tin and alloys; fluid flow; electricity, basic concepts and phenomena; light and optics; nonlinear optics; atomic and molecular physics; Materials Science;
Fields of Research : 03 Chemical Sciences > 0306 Physical Chemistry (incl. Structural) > 030606 Structural Chemistry and Spectroscopy
Socio-Economic Objective: E Expanding Knowledge > 97 Expanding Knowledge > 970103 Expanding Knowledge in the Chemical Sciences
Identification Number or DOI: 10.1039/c3dt53340a
URI: http://eprints.usq.edu.au/id/eprint/31954

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