Strong piezoelectricity and multiferroicity in BiFeO₃–BaTiO₃–NdCoO₃ lead-free piezoelectric ceramics with high Curie temperature for current sensing application

Lead-free piezoelectric and multiferroic ceramics of BiFeO₃–BaTiO₃–NdCoO₃ were synthesized by a conventional solid-state reaction method and the structural, piezoelectric, multiferroic and magnetoelectric properties of the materials were investigated. All the ceramics can be well sintered at a low sintering temperature of 980 °C for 2 h. The introduction of NdCoO₃ into BiFeO₃–BaTiO₃ induces a dramatic enhancement in the piezoelectricity, multiferroicity and magnetoelectric effect of the materials. After the addition of 1.0–3.0 mol% NdCoO₃, the ceramics possess a morphotropic phase boundary of rhombohedral and orthorhombic phases and exhibit high Curie temperature (~486–605 °C), strong piezoelectricity, good ferroelectricity and excellent temperature stability of piezoelectricity. The greatly enhanced magnetism with M _r = 0.4229 emu/g and M _s = 2.7186 emu/g is obtained in the ceramic with 8.0 mol% NdCoO₃, almost six times larger than that of an undoped ceramic. The ceramic with 2.0 mol% NdCoO₃ shows a strong magnetoelectric effect (α ₃₃ = 750 mV cm⁻¹ Oe⁻¹). The practical application potential of the present materials has also been preliminarily demonstrated by mimicking current monitoring. Our results suggest that the present ceramics may have potential applications in advanced lead-free piezoelectric and/or multiferroic devices.