Abstract
Li- and Ta-modified KNaNbO compounds are among the most promising lead-free ferroelectrics for high-sensitivity piezoelectric ceramic materials, and are potentially capable of replacing Pb(Zr,Ti)O. They are also being investigated as piezoelectric components in environmentally friendly magnetoelectric composites. However, most suitable modifications for this application have not been identified. We report here a simulation study of how the magnetoelectric voltage responses of layered composite structures based on Li(KNa)NbTaO varies with the chemical composition of the piezoelectric. Instead of relying on material coefficients from the literature, which would have required using different sources, an ad hoc set of materials was prepared. This demanded tailoring preparation by conventional means to obtain dense ceramics while controlling alkali volatilization, perovskite phase and microstructure, as well as characterizing their dielectric, elastic and electromechanical properties. This provided the set of relevant material coefficients as a function of composition, which was used to obtain the magnetoelectric responses of model layered structures including a reference magnetostrictive spinel oxide by simulation. The piezoelectric material leading to the highest magnetoelectric coefficient was identified, and shown to be different to that showing the highest piezoelectric coefficient. This reflects the dependence of the magnetoelectric response on all material coefficients, along with the complex interplay between composition, processing and properties in KNaNbO-based ceramics.
Highlights
Finding novel magnetoelectric (ME) materials with room temperature (RT) performance has been the objective of extensive research over the last few decades [1,2,3], because they can change the concept of electrical and magnetic devices, and enable a range of novel related technologies
The powders were initially characterized by X-ray diffraction (XRD) after the calcination step
A large piezoelectric response is associated with the orthorhombic-tetragonal polymorphic phase transition and two-phase coexistence
Summary
Finding novel magnetoelectric (ME) materials with room temperature (RT) performance has been the objective of extensive research over the last few decades [1,2,3], because they can change the concept of electrical and magnetic devices, and enable a range of novel related technologies. Activity is concentrated in two main lines: (1) single-phase multiferroics [4], and (2) composite approaches combining ferroelectric and ferromagnetic phases [5]. In spite of the extensive research, a single-phase multiferroic capable of enabling the anticipated ME technologies has not been developed [9]. One can obtain much larger magnetoelectric responses from the interaction of ferroelectric and ferromagnetic phases in a composite structure [10]. Co-fired ceramic layered structures of ferroelectric perovskite and magnetic spinel oxides provide enhanced reliability in applications, and are suitable for miniaturization [13]
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