Large single crystals of KNb3O8 and K4Nb6O17 can be grown by Czochralski pulling from the melt. In the case of KNb3O8 a small amount of excess K2O is used to avoid incongruent crystallization. Both materials show pronounced cleavage very similar to that of mica. The electrical properties of KNb3O8 are also very similar to those of mica, making this material a possible mica substitute as well as being an interesting new dielectric material in its own right. KNb3O8 is orthorhombic Pmmm, with a=8.91±0.01Aå,b=10.66±0.01Aå,c=3.77±0.01Aå , not the previously reported perovskite structure. Other characteristics determined include optical, mechanical, and chemical properties. When exposed to atmospheres between about 25 and 85% relative humidity, K4Nb6O17 becomes a trihydrate, with higher hydration above about 85% relative humidity. Optical, electrical, and structural properties of all three forms of K4Nb6O17 are described.

No abstract

No abstract

No abstract

Vitreous LiNbO3 and LiTaO3 have been prepared by roller quenching these compositions from the melt. The transparent glasses exhibit pronounced dielectric anomalies with peaks of ε≳105 close to the crystallization temperature which are not characteristic of the crystalline phase. Pyroelectricity is induced after cooling the glass in an electric field. The data are discussed in terms of a simple theoretical model for amorphous ferroelectricity and interfacial polarization due to localized ionic motion.