Vogel-Fulcher analysis of relaxor dielectrics with the tetragonal tungsten bronze structure : Ba6MNb9O30 (M = Ga, Sc, In)
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In-depth analysis of the relaxor behaviour of Ba6MNb9O30 (M= Ga, Sc, In) tetragonal tungsten bronze (TTB) ceramics was carried out. Powder x-ray diffraction and scanning electron microscopy were performed in order to confirm the formation of desired phases and to determine the microstructure. Low-temperature dielectric spectroscopy was used in order to characterise the dielectric properties of these materials; the degree of relaxor behaviour were investigated in relation with the increase of ionic radius of the M-cation on the B-site of the TTB structure. The dynamics of dielectric relaxation of dipoles was studied by fitting the dielectric permittivity data to the Vogel-Fulcher (VF) model in order to monitor the reproducibility and validity of the physical results. Restrictions to the VF fit were attempted besides the regular “free-fit” by constraining some of the fundamental relaxation parameters to physically sensible values. We show that Vogel-Fulcher fits are very sensitive to the fitting range resulting in a large range of fundamental parameters for the dielectric relaxation processes, and that the restriction of the frequency domain due to experimental noise or to instrumentation limits has a dramatic influence on the values obtained.
Rotaru , A & Morrison , F D 2015 , ' Vogel-Fulcher analysis of relaxor dielectrics with the tetragonal tungsten bronze structure : Ba 6 MNb 9 O 30 (M = Ga, Sc, In) ' Journal of Thermal Analysis and Calorimetry , vol. 120 , no. 2 , pp. 1249-1259 . DOI: 10.1007/s10973-014-4355-5
Journal of Thermal Analysis and Calorimetry
© Akadémiai Kiadó, Budapest, Hungary 2015. 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 publication is available at Springer via http://dx.doi.org/10.1007/s10973-014-4355-5
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