Ferroelectric Behavior in Barium Zirconium Metaniobate

Abstract

An unusual type of ferroelectric behavior has been observed in barium zirconium metaniobate, BaNb1.5Zr0.25O5.25. The orthorhombic, pseudotetragonal single crystal displays dielectric hysteresis only in its c direction, with normal dielectric properties in the a‐b plane. No evidence of a fist‐ or second‐order ferroelectric‐paraelectric transition has been observed up to 1400°C. The crystal melts incongruently at about 1525°C. A maximum in the dielectric constant occurs at 80°C. when measured at 103 c.p.s. but is not accompanied by any effect in the spontaneous polarization. The temperature of this k′ maximum has the frequency dependence of a dielectric relaxation process with an average activation energy of 0.2 e.v. These properties are consistent with the idea of a higher than second‐order ferroelectric‐paraelectric transition in this material. The dielectric behavior is explicable in terms of 180°“dipole aggregates” having a wide range of activation energies of reversal. There are suggestions in the technical literature of similar behavior in other materials.