K4Nb6O17—a new layer type ferroelectric

This paper reports K4Nb6O17, a mica type crystal grown in K2CO3-Nb2O5 system, to be a new layer type ferroelectric having a phase transition at 160°C. The room temperature structure is orthohombic. The ferroelectric transition has been confirmed with the study of temperature variation of its dielectric constant, conductivity, specific heat and AC-DC hysteresis as well as with DTA and high temperature X-ray analysis. An additional phase transition which may not be a ferroelectric one is also observed at 450°C. A structure model is also suggested.