Correlation between Phase Transitions and Piezoelectric Properties in Lead-Free (K,Na,Li)NbO3–BaTiO3 Ceramics

In this manuscript, we report the polymorphic phase transitions, structural changes and piezoelectric properties of alkali niobate based lead-free ceramics. The phase transitions were characterized as a function of alkali niobate content at room temperature. The results clearly demonstrate that in this system high piezoelectric properties are achieved for a specific fraction of ferroelectric orthorhombic (O) and tetragonal (T) phases. Using Rietveld and powder diffraction analysis, a correlation was established among the piezoelectric response, the fraction of O and T phases, and KNN ratio for three different systems of (K,Na)NbO3–BaTiO3 (KNN–BT), KNN–LiNbO3 (LN), and (K,Na,Li)NbO3 (KNLN)–BT.