Comparative study of two (K,Na)NbO3-based piezoelectric ceramics

Abstract

The piezoelectric performance of a ferroelectric ceramic is usually affected largely by the characters of domain structure inside its polycrystalline grains. However, relevant studies in the (K,Na)NbO3-based ceramics have been rarely carried out so far. This article reports the results of a systematical and comparative study between (K0.50Na0.50)0.94Li0.06NbO3 and (K0.50Na0.50)Li0.04(Nb0.85Ta0.15)O3 ceramics. Both of the two ceramics are of tetragonal phase at room temperature and have the orthorhombic-tetragonal phase transition close to room temperature. They exhibit high piezoelectric properties at room temperature and their piezoelectric properties are largely temperature-dependent. Interestingly, however, a much better piezoelectric thermal-aging stability is found in the (K0.50Na0.50)Li0.04(Nb0.85Ta0.15)O3 ceramic than in the (K0.50Na0.50)0.94Li0.06NbO3 ceramic. Furthermore, a marked difference in domain structure is recognized between the two ceramics through observing the domain patterns. The poled (K0.50Na0.50)0.94Li0.06NbO3 ceramic shows the complicated domain patterns consisting of banded parallel stripes and many watermarks inside most of the polycrystalline grains, whereas the other ceramic has the simple domain patterns that include a few sets of parallel stripes and some watermarks. The observed difference in piezoelectric thermal-aging stability between the two ceramics can be reasonably explained from the viewpoint of domain structure.