CO-EFFECT OF ANNEALING TEMPERATURE AND AMBIENT ON FERROELECTRIC PROPERTIES OF Bi_3.25La_0.75Ti₃O₁₂ FILMS

ABSTRACT

Co-effect of crystallization ambients (O₂ and N₂ mixed gas) and temperatures (600–800°C) on crystal structures and ferroelectric properties of the sol-gel deposited Bi_3.25La_0.75Ti₃O₁₂ (BLT) films is studied in this work. As the annealing temperature increases, the films get full crystallization and show different orientation. The film annealed in N₂ at 650°C is a-axis oriented, and get large P_r but bad fatigue property, which is caused by the charged oxygen vacancies in the films annealed in the oxygen-deficient ambients. The film annealed in 20% O₂ at 750°C is random oriented and exhibits excellent ferroelectric properties in terms of the largest P_r value of 11.5 μC/cm² and the lowest E_c value of 83.3 kV/cm under a voltage of 12 V. Moreover, the film shows good fatigue endurance after 10⁹ switching cycles. The crystllization and growth of the BLT films are sensitive to annealing ambients and temperatures. Therefore, the appropriate annealing ambient and temperature can improve the properties of the ferroelectric films greatly.

Keywords:

• Ferroelectric
• thin films
• sol-gel processing
• orientation

ACKNOWLEDGMENTS

This work is supported by the Key program of National Nature Science Foundation of China, No. 90407023. The authors gratefully acknowledge technical assistance from Analytical and Testing Center of Huazhong University of Science & Technology, China.