Revealing the solid-state processing mechanisms of antiferroelectric AgNbO3 for energy storage
2021
AgNbO3 is one of the prominent lead-free antiferroelectric (AFE) oxides, which
readily exhibits a field-induced AFE to ferroelectric phase transition and thus a
high energy storage density. The solid-statesynthesis of AgNbO3 is considered
difficult and an oxidizing atmosphere is typically employed during AgNbO3 processing,on the premise that oxygen can prevent possible decomposition of the silver oxide at high temperatures. However, details about the influence of processing parameters on the functional properties of AFE AgNbO3 are insufficiently understood. In this work, the solid-state
reaction of a stoichiometric AgO and Nb2O5 mixture was investigated. We found that ball milling can convert AgO into metallic Ag, which is beneficial for lowering the reaction temperature for the formation
of the perovskite phase to 500‒600℃.
Moreover, the influence of the processing
atmosphere (air, O2, and N2) was investigated by thermal analysis and in
situ X-ray
diffraction. Since the reaction between Ag and Nb2O5 to form AgNbO3
requires oxygen uptake, AgNbO3 was only found to form in air and O2, whereby
the kinetics were faster in the latter case. All the sintered AgNbO3 samples exhibited
a similar crystallographic structure, although the samples processed in
O2 had a lower oxygen vacancy concentration. Despite this, well-defined
AFE
double polarization loops were obtained in all cases. Our results indicate that
decomposition of sliver oxide during ball milling is beneficial for the solid-state
reaction, while a pure O2 atmosphere is not essential for the synthesis of high-quality
AgNbO3. These findings may simplify the processing and facilitate further
research of AgNbO3-based
antiferroelectrics.
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