Significantly enhanced piezoelectricity in low-temperature sintered Aurivillius-type ceramics with ultrahigh Curie temperature of 800 °C

We report an Aurivillius-type piezoelectric ceramic (Ca1-2x (LiCe)(x)Bi4Ti3.99Zn0.01O15) that has an ultrahigh Curie temperature (Tc) around 800 degrees C and a significantly enhanced piezoelectric coefficient (d(33)), comparable to that of textured ceramics fabricated using the complicated templating method. Surprisingly, the highest d(33) of 26 pC/N was achieved at an unexpectedly low sintering temperature (Ts) of only 920 degrees C (similar to 200 degrees C lower than usual) despite the non-ideal density. Study of different synthesized samples indicates that a relatively low Ts is crucial for suppressing Bi evaporation and abnormal grain growth, which are indispensable for high resistivity and effective poling due to decreased carrier density and restricted anisotropic conduction. Because the layered structure is sensitive to lattice defects, controlled Bi loss is considered to be crucial for maintaining structural order and spontaneous polarization. This low-T-s system is very promising for practical applications due to its high piezoelectricity, low cost and high reproducibility. Contrary to our usual understanding, the results reveal that a delicate balance of density, Bi loss and grain morphology achieved by adjusting the sintering temperature is crucial for the enhancing performance in Aurivillius-type high-T-c ceramics.