Tohru HIGUCHI, Takeshi HATTORI, and Takeyo TSUKAMOTO

Department of Applied Physics, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku, Tokyo 162-8601, Japan

(Received August 26, 2009; Accepted January 19, 2010)

Ba_2-xSr_xNaNb₅O₁₅ thin films were prepared on La_0.05Sr_0.95TiO₃ substrates by pulsed laser deposition. The structural and ferroelectric properties of the thin films depended on substrate temperature (T_sub) and Sr concentration. When T_sub was fixed at 700 °C, the Ba_2-xSr_xNaNb₅O₁₅ (x=0, 0.6, 1.0, and 1.4) thin films exhibited a high c-axis orientation. The thin films consisted of well-developed grains and exhibited a smooth surface. The c-axis-oriented Ba_0.6Sr_1.4NaNb₅O₁₅ thin film with the lowest Curie temperature also exhibited a high c-axis orientation and a P–E hysteresis loop with a high ferroelectricity at T_sub=650 °C. Thus, its remanent polarization (P_r) and coercive field (E_c) were 2P_r = 24.9 μC/cm² and 2E _c = 107kV/cm, respectively. These values indicate that Ba_2-xSr_xNaNb₅O₁₅ has ferroelectricity in the thin film form.

Key words: Ba_2-xSr_xNaNb₅O₁₅, thin film, La_0.05Sr_0.95TiO₃, pulsed laser deposition