Dielectric properties of BiFeO3 ceramics obtained from mechanochemically synthesized nanopowdersReport as inadecuate




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Journal of Electroceramics

, Volume 27, Issue 3–4, pp 154–161

First Online: 09 November 2011Received: 19 April 2011Accepted: 27 October 2011

Abstract

Dielectric behaviour of BiFeO3 ceramics, obtained by hot-pressing of nanopowders produced by mechanochemical synthesis from Bi2O3 and Fe2O3 oxides weight ratio 2:1, was studied in the temperature range 125–575 K. The ceramics was found to exhibit step-like dielectric response ε*T with high permittivity values, similar to the behaviour of materials with giant dielectric permittivity. Three overlapping relaxation processes contribute to the dielectric response: i relaxation in the low-temperature range 220–420 K, characterized by activation energy of 0.4 eV, ii relaxation in the temperature range 320–520 K with activation energy of 1.0 eV and iii broad dielectric anomaly in the vicinity of 420 K, which disappears after 1 h annealing at 775 K. The low-temperature relaxation is ascribed to the carrier hopping process between Fe and Fe ions. The presence of mixed valence of the Fe ions was proved by X-ray photoelectron spectroscopy. Dielectric relaxation in the middle-temperature range is considered as a result of grain boundary effect and internal barrier layers related to Bi25FeO40 phase as verified by X-ray diffraction. The high-temperature dielectric anomaly we relate to short-range hopping of ordered oxygen vacancies.

KeywordsBiFeO3 Powders-solid state reaction Defects Dielectric properties Electrical conductivity  Download fulltext PDF



Author: E. Markiewicz - B. Hilczer - M. Błaszyk - A. Pietraszko - E. Talik

Source: https://link.springer.com/







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