Investigation of the phase space in lead-free (K x Na1-x )1-y Li y (Nb1-z Ta z )O3 ferroelectric ceramics

Abstract

A library of ceramic compounds based on the lead-free (K x Na 1x ) 1y Li y (Nb 1z Ta z )O 3 solid solution has been synthesized and characterized using high-throughput experimentation (HTE) method. The phase space previously reported by Saito and Takao has been expanded to {{x, 0.1, 1.0}, {y, 0, 0.1}, {z, 0, 0.2}}, and new phase boundaries are observed. The relative density values show that with the appropriate sintering temperature, ~92% of the theoretical density can be reached. The relative permittivity values show that with increasing amount of K + and Ta 5+, the dielectric constant values increase. The effect of density on the dielectric constant values is however minimal. Resistivity values ranging from 10 9 to 10 13 Ω·cm are obtained for the samples. The piezoelectric charge coefficient values for selected compositions show that higher values are obtained close to the phase boundaries rather than away from them. The properties for the ceramic library using the HTE method are generally 15%-20% less than from the conventional method. This method is therefore more suited for screening of sample compositions than for producing samples with high piezoelectric properties.

Effect of bismuth titanate on the properties of potassium sodium niobate-based ceramics

“…Of the three KNN-based ceramics, KNN compositions have the lowest dielectric constant values followed by KNNLT compositions and finally KNNLST compositions. It has been reported that with isovalent element substitutions in KNN ceramics, both the sinterability and properties of the ceramics is improved [2,7,41]. The contributions to dielectric polarization in this case are possibly by electron shift within the molecules, the rotating dipolar molecules and/or the changing of ion places in the lattice.…”