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Characteristics of phase transitions in Ba0.995Na0.005Ti0.995Nb0.005O3 ceramics

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Author(s): W. Bąk

Journal: Archives of Materials Science and Engineering
ISSN 1897-2764

Volume: 39;
Issue: 2;
Start page: 75;
Date: 2009;
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Keywords: Ceramics | Phase transitions | Ferroelectrics | Dielectric spectroscopy

ABSTRACT
Purpose: The purpose of this work was to prepare ceramic material BaTiO3 (BT) as well as solid solution of Ba1-xNaxTi1-xNbxO3 (for x = 0.005) (BNTN05) type and correlate their structural (polycrystalline) properties with phase transitions within the temperature range from 153 K to 473 K.Design/methodology/approach: The dielectric spectroscopy method has been applied to measure dielectric and electric parameters within the frequency from 20 Hz to 1 MHz.Findings: The measured dependences of: complex dielectric permittivity and its phase angle (between measuring voltage and current response) points out on complex phase transition character for both investigated materials. Experimental outcomes for BT are consistent with those already published. Achieved results in the case of BNTN05 are published here for the first time. They were correlated with those of BT as unmodified one. Phase transitions parameters of both materials were described by means of generalised Curie-Weiss rule including step of phase transition diffusivity. Small amount (x = 0.005) of NaNbO3 (NN) admixture makes sharp, classical transition of first order kind occurring in the case of BT, to be a diffusive one and shifted by about 20 K towards lower temperatures.Research limitations/implications: Further investigations should be carried out in a broaden frequency range (up to 1.8 GHz) in order to establish the influence of network dynamics on ferroelectric-paraelectric phase transition as well as others low–temperature phase transitions. In order to complete structural data of new BNTN05 material additional X-ray and calorimetric measurements will be performed.Originality/value: The same method and components were used for preparation of BT and new BNTN05 material. Thermally induced phase transitions, mutually related in both materials were measured and described.
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