Vogel-Fulcher analysis of relaxor dielectrics with the tetragonal tungsten bronze structure : Ba6MNb9O30 (M = Ga, Sc, In)
Abstract
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.
Citation
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 . https://doi.org/10.1007/s10973-014-4355-5
Publication
Journal of Thermal Analysis and Calorimetry
Status
Peer reviewed
ISSN
1388-6150Type
Journal article
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