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Structural, Magnetic, and Electronic Studies of Complex Perovskites

King, Graham Missell
http://rave.ohiolink.edu/etdc/view?acc_num=osu1262114272

Abstract Details

2009, Doctor of Philosophy, Ohio State University, Chemistry.
This work describes the synthesis and characterization of a number of new AA'BB'O6 perovskites which possess the unusual combination of rock salt ordering of B/B' and layered ordering of A/A'. These compounds have been structurally characterized by powder X-ray and neutron diffraction as well as transmission electron microscopy. Several of these compounds are found to adopt polar P21 space group symmetry as a result of the cation ordering in combination with a–a–c+ octahedral tilting. A number of other compounds are shown to have a compositional modulation of the A-site cations that is accompanied by a twinning of the octahedral tilt system. Using UV-Vis spectroscopy the band gaps of these compounds have been determined. This analysis shows that NaLnMgWO6 compounds are insulators while NaLnMnWO6 compounds are semiconductors. The dielectric constants are found to be in the range of approximately 20-35. The magnetic properties of the NaLnMnWO6 and NaLnMgWO6 compounds have been measured. All NaLnMnWO6 compounds are found to order antiferromagnetically at temperatures ranging from 6-15 K. The NaLnMgWO6 compounds do not show any indications of magnetic order. The magnetic structures of NaLaMnWO6, NaNdMnWO6, and NaTbMnWO6 have been determined from neutron powder diffraction. NaLaMnWO6 is found to order into a simple commensurate structure. NaNdMnWO6 orders incommensurately due to interactions between the two magnetic ions. NaTbMnWO6 is found to pass through two magnetic phase transitions. Just below its Néel temperature it has an incommensurate modulation of its structure which disappears as it is further cooled.
Patrick Woodward, PhD (Advisor)
Yiying Wu, PhD (Committee Member)
Malcolm Chisholm, PhD (Committee Member)
171 p.
Chemistry
perovskite; perovskites; X-ray powder diffraction; neutron powder diffraction; TEM, UV-Vis; band gap; cation ordering; synthesis; magnetism; solid state; inorganic chemistry

Recommended Citations

Citations

  • King, G. M. (2009). Structural, Magnetic, and Electronic Studies of Complex Perovskites [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1262114272

    APA Style (7th edition)

  • King, Graham. Structural, Magnetic, and Electronic Studies of Complex Perovskites. 2009. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1262114272.

    MLA Style (8th edition)

  • King, Graham. "Structural, Magnetic, and Electronic Studies of Complex Perovskites." Doctoral dissertation, Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1262114272

    Chicago Manual of Style (17th edition)

osu1262114272
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© 2009, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.