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Synthesis, structure and dielectric properties of a new family of phases, ABC 3 O 11 : A = La, Pr, Nd, Sm, Gd; B = Zr, Hf; C = Ta, Nb

AuthorsRos, F.C.; Reeves-McLaren, N.; Masó, Nahum; West, A.R.
Issue Date24-Sep-2018
PublisherSpringer Nature
CitationJournal of the Australian Ceramic Society 55: 305-314 (2019)
AbstractEight new phases with the general formula of ABC O with different rare earth, (Zr, Hf), (Nb, Ta) combinations, have been prepared by solid-state reactions at a temperature range of 1200–1500 °C. The new phases—LaHfTa, LaHfNb, LaZrNb, PrHfTa, NdHfTa, NdHfNb, SmHfTa and GdHfTa—are characterised by X-ray and neutron diffraction data at room temperature and variable frequency impedance measurements. They are isostructural with LaZrTa O which consist of alternating single layers of UO pentagonal bipyramids and octahedra as shown by Rietveld refinement of X-ray and neutron powder diffraction data. Lattice parameters decrease with decreasing size of rare earth element substitution at A-site, and of all, Gd is the smallest rare earth that formed LaZrTa O analogues. Detailed attempts of attained and unattainable LaZrTa O analogues with different temperatures are included in this paper. All phases are highly insulating with temperature-independent bulk permittivities in the range 17 to 50; LaHfNb demonstrates the highest permittivity. Arrhenius plot shows that the activation energies are in the range 0.8 to 1.94 eV.
Publisher version (URL)http://dx.doi.org/10.1007/s41779-018-0236-x
Identifiersdoi: 10.1007/s41779-018-0236-x
issn: 2510-1579
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