Investigation of the phase space in lead-free (KxNa1-x)1-yLiy(Nb1-zTaz)O3 ferroelectric ceramics

Abstract

A library of ceramic compounds based on the lead-free (KxNa1−x)1−yLiy(Nb1−zTaz)O3 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 Ta5+, the dielectric constant values increase. The effect of density on the dielectric constant values is however minimal. Resistivity values ranging from 109 to 1013 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.