Dielectric and piezoelectric properties of alkaline-earth titanate doped (K0.5Na0.5)NbO3 ceramics

(K0.5Na0.5)NbO3 (KNN) and 0.995(K0.5Na0.5)NbO3–0.005AETiO3 (AE = Mg, Ca, Sr, Ba) were successfully prepared by conventional ceramic processing and without the cold-isostatic-pressing (CIP) process. The effects of low AETiO3 (AET) concentration on crystal structure, density, dielectric and piezoelectric properties of the KNN based ceramics were evaluated. The results show that adding MgTiO3(MT) and BaTiO3(BT) to KNN can lead to the appearance of a trace amount of second phase(s), reduced density and deteriorated electrical properties. Adding CaTiO3(CT) and SrTiO3(ST) to KNN can promote densification and optimize electrical properties. Two phase transitions at Tt–o ( the temperature at which the phase transition from orthorhombic to tetragonal occurs) and Tc (the Curie temperature) were observed in KNN and all KNN–AET ceramics, by using differential scanning calorimetry (DSC) analysis and dielectric characterization. Adding AET to KNN caused the variations of Tt–o and Tc.