SYNTHESIS AND PHASE ANALYSIS OF A NEW FERROELECTRIC (K0.5Na0.5)NbO3–Bi0.5K0.5TiO3–BaTiO3 TERNARY SOLID SOLUTION

In order to develop new lead-free pieozoelectric/ferroelectric materials, the y( K0.5Na0.5 ) NbO3 – (1 - y)[(1 - x) Bi0.5K0.5TiO3 – x BaTiO3 ] solid solution system is synthesized and the partial ternary phase diagram in the KNN-rich region with compositions of y = 0.98 to y = 0.96 is established. All the compositions studied show a gradual phase change from a tetragonal to an orthorhombic structure as the BT component increases. A mixture of tetragonal and orthorhombic phases is found in the composition range of x = 0.25 to 0.60 and y = 0.97, and x = 0.50 to 0.75 and y = 0.96, indicating a ternary morphotropic phase boundary region. The piezoelectric and ferroelectric properties of the 0.97(KNN)–0.03[0.60BKT–0.40BT] ceramics are characterized. The increase in remnant polarization as compared with pure KNN shows improved ferroelectricity by forming the ternary solid solution.