Effect of Ti on the properties of (KxNa1−x)NbO3 based lead-free ceramics

Abstract

The effect of modifying lead-free alkaline niobate based piezoelectric ceramics with different amounts of Ti has been investigated. Thermal studies using a dilatometer show that increasing Ti amount leads to decreasing sintering temperature by approximately 11.7°C for every 1mol% of the dopant added. Chemical analysis on the ceramics reveals that the measured amounts of the alkali elements are slightly lower while small amounts of Zr were introduced to the ceramic through the milling process. Microstructural analysis shows that that the average grain size decreases with increasing dopant amount and that new, smaller sized grains are formed in the presence of Ti. Two-phase orthorhombic–tetragonal diffraction patterns are observed using synchrotron X-ray diffraction while the analysis using Rietveld refinement shows that the fraction of the tetragonal phase in the two-phase patterns increase with increasing Ti content. The dielectric, piezoelectric coefficient values and ferroelectric properties of the ceramics decrease with increasing Ti amount. The current density values in the samples increase by up to 5 orders of magnitude when more than 0.5mol% of the dopant is added.