@conference{
author = "Ilić, Nikola and Bobić, Jelena and Džunuzović, Adis and Vijatović Petrović, Mirjana and Stojanović, Biljana",
year = "2018",
abstract = "Multiferroic materials exhibit at least two of the so-called ferroic properties (ferroelectric,
(anti)ferromagnetic and ferroelastic) in the same time. They are very interesting
from the theoretical point of view because of a different nature of those
properties, but coupling between the properties opens up huge possibilities for application
as magnetoresistors, memory devices, sensors and many other devices [1].
Being ferroelectric up to 830 °C and antiferromagnetic (weakly ferromagnetic) up
to 370 °C, bismuth ferrite (BiFeO3) is one of the very few room-temperature singlephase
multiferroic materials and one of the most studied ceramic materials in the
last two decades. BiFeO3 has also good potential to be used as a pigment, catalyst,
photocatalyst or solar cell material [1,2].
However, because of specific obstacles in obtaining pure, dense and highly resistive
ceramics, harnessing of those properties is still far from being achieved and the
possibility of its application as a multiferroic material is arguable. High volatility
of bismuth above 800 °C and thermodynamic instability of BiFeO3 between 447 °C
and 767 °C make the densification of BiFeO3 ceramics very difficult, especially by
conventional methods. High leakage currents in BiFeO3 (originating mostly from
oxygen and bismuth vacancies) disable ceramic samples to be polarized and to
exhibit ferroelectric properties. Spiral structure of magnetic moments lowers the
coupling between ferroelectric and magnetic orders [3,4].
BiFeO3 ceramic materials presented in this study were synthesized by autocombustion
method with idea to lower the temperature needed for effective sintering
in order to prevent volatilisation and improve the density and phase composition.
Auto-combustion is a type of sol-gel route which enables high homogeneity in
solutions stabilized by organic compounds, which oxidize vigorously producing the ash powders as a wanted product. Because of such fast reaction, the defects
are incorporated into structure enabling solid state sintering to take place at
lower temperatures and more quickly. Presented microstructures are illustrating
the usual problems that occur during the synthesis of powders and processing of
ceramic materials. Powders tend to agglomerate, and although the agglomerates
can be destroyed by milling (Figure 1), this process often disturbs the phase
composition of ceramics synthesized from the milled powders. Because of a wide
range of temperatures at which bismuth evaporates and secondary phases form, it
is important to conduct heating and cooling of samples very fast (quenching), but
even this way some secondary phases are formed (Figure 2) and densification is not
complete (Figure 3).
The study presents the evolution of the mentioned problems during attempts to
overcome them by modification of the synthesis conditions, by using different
treatments of the powders and by modification of the sintering process.",
publisher = "Serbian Academy of Sciences and Arts Knez Mihailova 35, 11000 Belgrade, Serbia Phone: +381 11 2027200 https://www.sanu.ac.rs/en/",
journal = "First International Conference Elmina, Belgrade, Serbia, 27-29 August 2018",
title = "Problems in Obtaining High-Density, Pure-Phase BiFeO3 Ceramics",
url = "https://hdl.handle.net/21.15107/rcub_rimsi_2598"
}
