Microstructural and high-temperature impedance spectroscopy study of Ba6MNb9O30 (M=Ga, Sc, In) relaxor dielectric ceramics with tetragonal tungsten bronze structure
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This work reports on the microstructural and high-temperature impedance spectroscopy study of a family of dielectric ceramics Ba6MNb9O30 (M=Ga, Sc, In) of tetragonal tungsten bronze (TTB) structure with relaxor properties. For Ba6GaNb9O30 and Ba6InNb9O30 pellets, the SEM images have revealed good, dense internal microstructures, with well-bonded grains and only discrete porosity; in contrast Ba6ScNb9O30 pellets had a poorer microstructure, with many small and poorly-bonded grains gathered in agglomerates, resulting in significant continuous porosity and poorly defined grain boundary regions. The electroactive regions were characterised by the bulk and grain boundaries capacitances and resistances, while their contribution to the electrical conduction process was estimated by determining activation energies from the temperature (Arrhenius) dependence of both electric conductivities and time constants. For Ga and In analogues the electronic conductivity are dominated by the bulk response, while for Sc analogue, the poorly defined grain boundaries give a bulk-like response, mixing with the main bulk contribution.
Rotaru , A & Morrison , F D 2016 , ' Microstructural and high-temperature impedance spectroscopy study of Ba 6 MNb 9 O 30 (M=Ga, Sc, In) relaxor dielectric ceramics with tetragonal tungsten bronze structure ' Ceramics International , vol 42 , no. 10 , pp. 11810-11821 . DOI: 10.1016/j.ceramint.2016.04.102
© 2016 Published by Elsevier Ltd. This work is made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://dx.doi.org/10.1016/j.ceramint.2016.04.102
The authors would like to thank to the following funding organisations: the Royal Society for providing a research fellowship (F.D.M.), EPSRC for providing the PhD student grant (A.R.) and Roberto Rocca Education Program for providing an additional fellowship (A.R.).
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