Dielectric and piezoelectric properties of alkaline-earth titanate doped (K_(0.5)Na_(0.5))NbO_3 ceramics

摘要

(K_(0.5)Na_(0.5))NbO_3 (KNN) and 0.995(K_(0.5)Na_(0.5))NbO_3-0.005AETiO_3 (AE=Mg, Ca, Sr, Ba) were successfully prepared by conventional ceramic processing and without the cold-isostatic-pressing (CIP) process. The effects of low AETiO_3 (AET) concentration on crystal structure, density, dielectric and piezoelectric properties of the KNN based ceramics were evaluated. The results show that adding MgTiO_3(MT) and BaTiO_3(BT) to KNN can lead to the appearance of a trace amount of second phase(s), reduced density and deteriorated electrical properties. Adding CaTiO_3(CT) and SrTiO_3(ST) to KNN can promote densification and optimize electrical properties. Two phase transitions at T_(t-o) (the temperature at which the phase transition from orthorhombic to tetragonal occurs) and T_c (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 T_(t-o) and T_c.