Upside – down composites
Piezoelectric materials have a multi-billion dollar impact on the electromechanical transducers market. Their conventional synthesis includes a sintering step (at over 1000 °C) that often hampers direct integration into monolithic devices and confines their applications to heterostructures made using tedious multi-step assembly or to composites with poor electromechanical behavior. Here, we demonstrate a new and easy to scale method for the integration of piezoelectric ceramics at ultra-low temperatures without compromising their functionality. We show that all-ceramic “upside-down” composites with exceptionally high fractions of piezoelectric filler (−75 vol. %) and low porosity can be achieved using aqueous dispersion of lithium molybdate as a binder. The method is based only on coating, mixing, moulding and drying sequences. The measured piezoelectric charge coefficient, d33 −84 pC·N−1, outperforms any other known composite, whereas the voltage constant, g33 –33 mV m·N−1, competes with bulk materials, thus paving the way for versatile applications not previously considered.