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



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


The crystal structure and thermal expansions of a new tetragonal tungsten bronze (TTB) ferroelectrics Pb2K0.5Li0.5Nb5O15 were systematically investigated by selected area electron diffraction (SAED), neutron powder diffraction, synchrotron XRD, and high temperature XRD. SAED and Rietveld refinement reveal that Pb2K0.5Li0.5Nb5O15 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.
Inorganic Chemistry


Thermal expansion, tungsten bronze, ordering, crystal structure


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 Pb<sub>2</sub>K<sub>0.5</sub>Li<sub>0.5</sub>Nb<sub>5</sub>O<sub>15</sub>, Inorganic Chemistry, [online], (Accessed May 19, 2024)


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Created August 11, 2014, Updated October 12, 2021