Studies on the System (1-x) NaNbO₃ xKTaO₃

抄録

The phase diagram of the system (1-x) NaNbO₃ xKTaO₃ 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\lesssimx<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.