Preparation of Barium Titanate–Potassium Niobate Solid Solution System Ceramics and Their Piezoelectric Properties

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Barium titanate (BaTiO3, BT)–potassium niobate (KNbO3, KN) solid solution system ceramics were prepared by normal sintering, and their piezoelectric properties were measured. The phase diagram of the BT–KN system was investigated by dielectric measurement and X-ray diffraction (XRD). The Curie temperature ($T_{\text{C}}$) was almost constant at approximately 130 and 430 °C for ceramics with KN contents below and above 50 mol %, respectively. At room temperature, two phases, ferroelectric tetragonal and ferroelectric orthorhombic, coexisted in the composition range from 0.7BT–0.3KN to 0.1BT–0.9KN. This system was found to be a limited solid solution system that involves BT- and KN-rich phases. Their piezoelectric properties were investigated on the basis of the electric-field dependence of strain measurements. For ceramics with KN contents below 30 mol %, the apparent piezoelectric constant ($d_{33}$) decreased approximately with increasing KN content, whereas above 30 mol %, the apparent $d_{33}$ increased as a function of KN content.
2008-09-25