Ordered Structure and Thermal Expansion in Tungsten Bronze Pb2K0.5Li0.5Nb5O15

Published

August 12, 2014

Author(s)

Kun Lin, Yangchun Rong, Hui Wu, Qingzhen Huang, Li You, Yang Ren, Longlong Fan, Jun Chen, Xianran Xing

Abstract

The crystal structure and thermal expansions of a new tetragonal tungsten bronze (TTB) ferroelectrics Pb₂K_0.5Li_0.5Nb₅O₁₅ were systematically investigated by selected area electron diffraction (SAED), neutron powder diffraction, synchrotron XRD, and high temperature XRD. SAED and Rietveld refinement reveal that Pb₂K_0.5Li_0.5Nb₅O₁₅ displays a commensurate superstructure of simple orthorhombic TTB structure at room temperature. The structure can be described with space group Bp2₁m. The transition to paraelectric phase (P4/mbm) occurs at 500 °C. Compared with Pb₂KNb₅O₁₅ (PKN), the substitution of K⁺ with small Li⁺ into PKN causes the tilting of NbO₆ octahedra away from c axis with Δ}θ approximately equal} 10 ° and raises the Curie temperature by 40 °C, and the negative thermal expansion coefficient (TEC) along polar b axis increases more than 50% in the temperature range 25 °C 500 °C. We present that, by introduction of Li⁺, the enhanced spontaneous polarization are responsible for the enhanced negative thermal expansion along b axis, which may be caused by more Pb^2+^ in the pentagonal caves.

Citation

Inorganic Chemistry

Volume

53

Pub Type

Journals

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Keywords

Thermal expansion, tungsten bronze, ordering, crystal structure

Citation

Lin, K. , Rong, Y. , Wu, H. , Huang, Q. , You, L. , Ren, Y. , Fan, L. , Chen, J. and Xing, X. (2014), Ordered Structure and Thermal Expansion in Tungsten Bronze Pb₂K_0.5Li_0.5Nb₅O₁₅, Inorganic Chemistry, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=916678 (Accessed April 19, 2024)