Hydrothermal growth of c-axis oriented ferroelectric (Bi1/2K1/2)TiO3 films on metal substrates

• Published in: Thin solid films Vol. 713; p. 138342
• Main Authors: Yamamoto, Masayoshi, Sakurai, Ryotaro, Hagiwara, Manabu, Fujihara, Shinobu
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.2020
• Subjects: Ferroelectrics; Film growth; Hydrothermal method; Low-temperature synthesis; Metal substrates; Hydrothermal method; Metal substrates; Ferroelectrics; Low-temperature synthesis; Film growth
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2020.138342

•Growth of (Bi1/2K1/2)TiO3 films on Ni-based metal substrates is reported.•LaNiO3 was used as a buffer layer.•(Bi1/2K1/2)TiO3 films were grown by a hydrothermal reaction at 150 °C.•Ferroelectric polarization hysteresis was observed. Ferroelectric films fabricated on metal substrates are desirable for use in piezoelectric vibration energy harvesters. In this report, we demonstrate that dense films of lead-free ferroelectric (Bi1/2K1/2)TiO3 (BKT) with preferred c-axis orientation can be grown on nickel-based alloy substrates by utilizing the hydrothermal synthesis method. A buffer layer of LaNiO3 (LN) was formed on the substrates by the sol-gel spin coating method, and then BKT was grown by a hydrothermal reaction at a low temperature of 150 °C. The surface structure and thickness of the final BKT films were found to strongly depend on the numbers of the deposition cycles for LN and BKT, respectively. As a result, highly c-axis oriented BKT films with a smooth surface and a thickness up to 830 nm were obtained. Although the as-deposited BKT films were suggested to contain hydroxyl groups in their crystal lattice, a post-annealing process at 650 °C in air was found to be effective to remove them. The polarization response of the annealed BKT film proved the ferroelectric polarization switching in the film.