The phase diagram of the system (1-
x) NaNbO
3 xKTaO
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\lesssim
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.
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