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.