Precipitate-domain wall topologies in hardened Li-doped NaNbO3

Ferroelectric hardening is an absolute requirement for potential applications of piezoceramics in high-power devices. A very recent work demonstrates that ferroelectric hardening by pinning domain walls with precipitates introduced during processing is feasible, akin to precipitation hardening in metals. With the precipitation of plate-like LiNbO3 in Li-doped NaNbO3 piezoceramics, ferroelectric hardening was achieved, exhibiting an enhanced mechanical quality factor (Qm). The specific morphology and corresponding orientation of the LiNbO3 platelets, exhibiting {110}PC habit planes, were characterized by transmission electron microscopy (TEM). The experimentally revealed crystallographic structures and strain incompatibility were found to correlate well with the thermodynamic simulation of the minimum-energy aspect ratio. In particular, the topology of the precipitate-domain wall assembly was clarified, revealing a full pinning on the domain walls by the incorporated plate-like precipitates. The revealed topology provides a fundamental basis for future optimization strategies for platelet hardening in new lead-free piezoceramics for high-power applications. In this work, plate-like LiNbO3 precipitates habiting on {110}PC of NaNbO3 piezoceramics were designed with the appropriate aging schemes. The morphology of the precipitate, the orientation relationship of the platelet with respect to the domain wall, and the accessible hardening schemes were unveiled by transmission electron microscopy. Experimental assessment of the strain incompatibility by matrix-precipitate interface misfit and thermodynamic simulation of the equilibrium shape is in good correlation. In particular, the topology of the precipitate-domain wall assembly was clarified, revealing full pinning on the domain walls by the incorporated plate-like precipitates. This provides a fundamental basis for future optimization strategies for platelet hardening in new lead-free piezoceramics for high-power applications. [Display omitted]