Structure of 18R shifted hexagonal perovskite La{sub 6}MgTi{sub 4}O{sub 18} revisited by neutron diffraction

Lu, Fengqi; Kuang, Xiaojun

doi:10.1016/J.JSSC.2014.09.032

Title: Structure of 18R shifted hexagonal perovskite La{sub 6}MgTi{sub 4}O{sub 18} revisited by neutron diffraction

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Abstract

The structure of 18-layer shifted B-site deficient hexagonal perovskite La{sub 6}MgTi{sub 4}O{sub 18} compound has been re-examined by neutron powder diffraction. Structural analysis reveals that La{sub 6}MgTi{sub 4}O{sub 18} compound adopts a 18R octahedral-tilted structure with LaO{sub 3} layer stacking sequence of (hhcccc){sub 3} in space group R{sup {sup -}}3, in contrast with the previously proposed R3m. La{sub 6}MgTi{sub 4}O{sub 18} demonstrates partially ordered Mg cation distribution with a preference on the central octahedral sites over the outer octahedral sites in the cubic perovskite blocks isolated by the single vacant octahedral layers between the two consecutive hexagonal layers. The instability of the La{sub 6}MgTi{sub 4}O{sub 18} on alumina ceramic substrate at high temperature and its dependencies of cell parameters and permittivity were characterized as well. - Graphical abstract: 18-layer shifted hexagonal perovskite La{sub 6}MgTi{sub 4}O{sub 18} adopts octahedral-tilted structure in R{sup {sup -}}3 and demonstrates partially ordered Mg distribution in the cubic perovskite blocks isolated by the vacant octahedral layers. - Highlights: • Neutron diffraction reveals an octahedra-tilted structure in R{sup {sup -}}3 for La{sub 6}MgTi{sub 4}O{sub 18}. • Mg/Ti distribution in La{sub 6}MgTi{sub 4}O{sub 18} is partially ordered in the perovskite blocks. • Instability of La{sub 6}MgTi{sub 4}O{sub 18}more »« less

Authors:: Lu, Fengqi; Kuang, Xiaojun

Publication Date:: Thu Jan 15 00:00:00 EST 2015

OSTI Identifier:: 22436669

Resource Type:: Journal Article

Journal Name:: Journal of Solid State Chemistry

Additional Journal Information:: Journal Volume: 221; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0022-4596

Country of Publication:: United States

Language:: English

Subject:: 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ALUMINIUM OXIDES; CATIONS; CERAMICS; DIELECTRIC MATERIALS; DISTRIBUTION; LANTHANUM OXIDES; NEUTRON DIFFRACTION; PERMITTIVITY; PEROVSKITE; SPACE GROUPS; SUBSTRATES; TRIGONAL LATTICES

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                    Lu, Fengqi, and Kuang, Xiaojun. Structure of 18R shifted hexagonal perovskite La{sub 6}MgTi{sub 4}O{sub 18} revisited by neutron diffraction.  United States: N. p., 2015. 
        Web.  doi:10.1016/J.JSSC.2014.09.032.

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                    Lu, Fengqi, & Kuang, Xiaojun. Structure of 18R shifted hexagonal perovskite La{sub 6}MgTi{sub 4}O{sub 18} revisited by neutron diffraction.  United States.  https://doi.org/10.1016/J.JSSC.2014.09.032

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                    Lu, Fengqi, and Kuang, Xiaojun. 2015.  
        "Structure of 18R shifted hexagonal perovskite La{sub 6}MgTi{sub 4}O{sub 18} revisited by neutron diffraction".  United States.  https://doi.org/10.1016/J.JSSC.2014.09.032.

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@article{osti_22436669,

  title        = {Structure of 18R shifted hexagonal perovskite La{sub 6}MgTi{sub 4}O{sub 18} revisited by neutron diffraction},

  author       = {Lu, Fengqi and Kuang, Xiaojun},

  abstractNote = {The structure of 18-layer shifted B-site deficient hexagonal perovskite La{sub 6}MgTi{sub 4}O{sub 18} compound has been re-examined by neutron powder diffraction. Structural analysis reveals that La{sub 6}MgTi{sub 4}O{sub 18} compound adopts a 18R octahedral-tilted structure with LaO{sub 3} layer stacking sequence of (hhcccc){sub 3} in space group R{sup {sup -}}3, in contrast with the previously proposed R3m. La{sub 6}MgTi{sub 4}O{sub 18} demonstrates partially ordered Mg cation distribution with a preference on the central octahedral sites over the outer octahedral sites in the cubic perovskite blocks isolated by the single vacant octahedral layers between the two consecutive hexagonal layers. The instability of the La{sub 6}MgTi{sub 4}O{sub 18} on alumina ceramic substrate at high temperature and its dependencies of cell parameters and permittivity were characterized as well. - Graphical abstract: 18-layer shifted hexagonal perovskite La{sub 6}MgTi{sub 4}O{sub 18} adopts octahedral-tilted structure in R{sup {sup -}}3 and demonstrates partially ordered Mg distribution in the cubic perovskite blocks isolated by the vacant octahedral layers. - Highlights: • Neutron diffraction reveals an octahedra-tilted structure in R{sup {sup -}}3 for La{sub 6}MgTi{sub 4}O{sub 18}. • Mg/Ti distribution in La{sub 6}MgTi{sub 4}O{sub 18} is partially ordered in the perovskite blocks. • Instability of La{sub 6}MgTi{sub 4}O{sub 18} on alumina ceramic at high temperature is demonstrated.},

  doi          = {10.1016/J.JSSC.2014.09.032},

  url          = {https://www.osti.gov/biblio/22436669},
  journal      = {Journal of Solid State Chemistry},

  issn         = {0022-4596},

  number       = ,

  volume       = 221,

  place        = {United States},

  year         = {Thu Jan 15 00:00:00 EST 2015},

  month        = {Thu Jan 15 00:00:00 EST 2015}

}

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