New lead-free piezoelectric ceramics derived from the K0.5Na0.5NbO3-AgNbO3 solid solution system

Lead-based ferroelectrics, such as Pb(Zr,Ti)O3 and Pb(Mg1/3Nb2/3)O3-PbTiO3 [1], [2], are widely used for piezoelectric actuators, sensors and transducers due to their excellent piezoelectric properties. However, recent concern about the toxicity of lead requires more environmentally friendly lead-free piezoelectric materials. Potassium sodium niobate (K0.5Na0.5NbO3, KNN) has been recognized as one of the promising candidates for lead-free piezoelectric host materials. Hot pressed KNN ceramics have been reported to have good piezoelectric properties of d33=160 pC/N and kp=45%, along with a high Curie temperature (TC ~420 ??C) [3], [4]. However, KNN ceramics are difficult to sinter by the conventional solid state method and subject to the deliquescence problem. On the other hand, silver niobate (AgNbO3, AN) has attracted renewed interest because it is a lead-free ferroelectric with a gh TC of 360 ??C [5]. The objective of this work is to investigate this new lead-free solid solution system of (1-??)K0.5Na0.5NbO3-??AgNbO3 [(1-??)KNN-??AN], in order to improve the piezoelectric properties by enhancing the sinterability of KNN.