Improvement of the piezoelectric and ferroelectric properties of (K, Na)0.5NbO3 ceramics via two-step calcination-milling route

A second calcination milling step was introduced in the conventional processing of (K, Na)(0.5)NbO3 (KNN) ceramics (sintered in air) to further homogenenize the particle size distribution of the pre-sintered powders. The ceramic derived from the powders prepared by the two-step route possesses grains with better uniformity and is more compact. The relative density of the bulk ceramic reached 96.9%. Excellent properties are obtained in as-prepared KNN ceramics with k(p)=44%, d(33)=111 pC/N, tan delta=0.85%, epsilon(T)(33)/epsilon(0)=311, Q(m)=193, P-r=25.4 mu C/cm(2), d(33)*=251 pm/V, which are superior to those of the ceramics derived from the powders calcined once as used in the traditional processing. These results indicate that twice-calcination milling route is shown to be a facile and effective way to simultaneously improve the piezoelectric and ferroelectric properties of KNN ceramics without sintering aids. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.