The objective of the present project is the study of the grain-size effect on the di-, ferro- and piezoelectric characteristics of alkali niobate nanocrystalline piezoceramics. This material system has attracted much attention in recent years due to the potential of being a environment friendly alternative to the lead containing compositions on the basis of lead-titanate-zirconate. For these traditional piezoelectric ceramics the effect of crystallite size on the electric properties is quite well understood.
In the case of alkaline niobates, however, almost no information is available in the scientific literature. The proposed project therefore aims to systematically treat this subject. For this purpose nanosized powders with an average particle size i n the range of 10 to 100 nm will be prepared by micro-emulsion mediated synthesis. This synthesis approach allows the synthesis of tailor made ceramic particles with a very narrow particle size distribution, since nucleation and growth during particle formation are confined to the volume of individual micelles, acting as nanoreactors. Dense nanocrystalline bulk ceramics, with a wide range of grain-sizes from approximately 100nm up to several microns will be prepared by pressure assisted consolidation in order to reduce the extend of grain growth during sintering.
Powders and ceramics will be characterized, with respect to purity, composition, crystallite size using X-ray diffraction, electron microscopy (SEM, TEM, HR-TEM) and chemical analytical means (IC P-OES, Raman-spectroscopy) in order to optimise the processing procedure. The functional characterization of the ceramics will comprise dielectric spectroscopy, measurements of the ferroelectric hystereses and piezoelectric measurements over the whole temperature range of piezoelectric activity. The expected outcome of the present research is an extensive description and understanding of the size effect in lead free piezoceramics based on alkali niobates.
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