Piezoelectric and Dielectric Properties of Ceramics in the System Potassium—Sodium Niobate

High radial coupling coefficients are observed for compositions having up to 50 mole % sodium niobate additions to potassium niobate. The activity diminishes with additional sodium niobate content and disappears beyond about 98 mole % additions. Dielectric constants are relatively low, varying from 450 to 125, depending on composition. A.‐c. losses are high and d.‐c. resistivities are ∼10 12 ohm‐cm. The low dielectric constants and high coupling obtained in certain regions of the system make these materials promising for solid ultrasonic delay line use, especially where thin sectioned plates are required, as in high‐frequency thickness extensional or thickness shear mode transducers.