Ferroelectric properties of the KSr₂Nb₅O₁₅-LaNb₃O₅ system

We find that many compositions of the form M+M22+Nb5O15 (M+ = Na, K, Rb; M2+ = Sr, Ba) have the tungsten-bronze structure and are ferroelectric. The coefficients of the Devonshire free energy function are determined for crystals in the KSr2Nb5O15 - LaNb3O9 system. The results show that very large room temperature linear electro-optic coefficients can be obtained. © 1968.