Ferroelectricity in the Compound ${\mathrm{Ba}}_2$${\mathrm{Bi}}_4$${\mathrm{Ti}}_5$${\mathrm{O}}_{18}$

Some ferroelectric and crystallographical properties of the compound ${\mathrm{Ba}}_2$ ${\mathrm{Bi}}_4$ ${\mathrm{Ti}}_5$ ${\mathrm{O}}_{18}$ are presented. The compound represents a new structure with the unit cell consisting of one ${\mathrm{Bi}}_2$ ${\mathrm{O}}_2^{2+}$ layer and five perovskite layers. From -196° to +580°C, a maximum in the real part of the dielectric constant was observed at 329°C. No thermal hysteresis was observed within the precision of ±2°C. A remanent polarization of 2×${10}^{-6\mathrm{}}$ coul/${\mathrm{cm}}^2$ and a coercive field of 10 kv/cm were observed at room temperature.