Studies on the System (1-x) NaNbO3 xKTaO3

The phase diagram of the system (1- x ) NaNbO 3 x KTaO 3 is determined by means of the dielectric constant measurements, x -ray diffraction and differential thermal analysis. In the solid solutions with the composition range of x >0.1, the homogeneous phases appear. The Curie point, i.e. the transition point from cubic to tetragonal phase, varies linearly from 360°C ( x =0.1) to -120°C ( x =0.8) with increasing value of x . The other transition temperature from tetragonal to orthorhombic phase also decreases linearly from 240°C to -140°C. In the range of \(0.025{}x{<}0.1\), a heterogeneous phase, consisting of the mixture of the ferroelectric and the antiferroelectric compounds, appears. The dielectric constant vs. temperature curve in this range shows two peaks at 360°C and 340°C. It was confirmed that these two anomalies correspond to the transition of both end compound of the heterogeneous phase, i.e. x ≈0.1 and x ≈0.025. in the range of x <0.025, the other homogeneous antiferroelectric phase appears.