Abstract
We report on a heterogeneity study, down to the atomic scale, on a representative multiple-element-modified ceramic based on potassium sodium niobate (KNN): 0.95(Na0.49K0.49Li0.02)(Nb0.8Ta0.2)O3–0.05CaZrO3 with 2 wt % MnO2. We show that different routes for incorporating the MnO2 (either before or after the calcination step) affect the phase composition and finally the functionality of the material. According to X-ray diffraction and scanning electron microscopy analyses, the ceramics consist of orthorhombic and tetragonal perovskite phases together with a small amount of Mn-rich secondary phase. The addition of MnO2 after the calcination results in better piezoelectric properties, corresponding to a ratio between the orthorhombic and tetragonal perovskite phases that is closer to unity. We also show, using microscopy techniques combined with analytical tools, that Zr-rich, Ta-rich and Mn-rich segregations are present on the nano and atomic levels. With this multi-scale analysis approach, we demonstrate that the functional properties are sensitive to minor modifications in the synthesis route, and consequently to different material properties on all scales. We believe that detecting and learning how to control these modifications will be a step forward in overcoming the irreproducibility problems with KNN-based materials.
Highlights
As European legislation limits the use of lead-based piezoelectrics [1], there are high expectations for materials based on potassium sodium niobate (KNN)
As the Mn-AC ceramic showed a superior piezoelectric response, we further investigated its domain structure using TEM and selected-area electron diffractions (SAED) analyses
We showed experimentally that the structure and chemistry of the ceramic were
Summary
As European legislation limits the use of lead-based piezoelectrics [1], there are high expectations for materials based on potassium sodium niobate (KNN). In 2004, who reported an improved piezoelectric coefficient for Ta- and Li-modified KNN, comparable with that of lead-based materials [2]. It was envisaged, for the first time, that a modified KNN could overcome the problem of the modest piezoelectric activity of pure KNN ((K0.5 Na0.5 )NbO3 ), triggering the development of a lead-free piezoelectric market. Multiple-element modifications of KNN are used to increase its functionality. The piezoelectric activity is increased by introducing phase coexistence at room temperature. Since densification is challenging in KNN [4], the synthesis usually involves sintering aids such as MnO2 [5], ZnO [6], (K,Na)-germanate [7] or Cu-based materials [8]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
