Structural and electrical characterization of hydrothermally deposited piezoelectric (K,Na)(Nb,Ta)O3 thick films

Takahisa Shiraishi, Yuta Muto, Yoshiharu Ito, Takanori Kiguchi, Kazuhisa Sato, Masahiko Nishijima, Hidehiro Yasuda, Hiroshi Funakubo, Toyohiko J. Konno

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)


(K0.89Na0.11)(Nb0.85Ta0.15)O3 thick films were epitaxially grown at 200 °C on (001)La:SrTiO3 and (001)cSrRuO3//(001)SrTiO3 substrates by hydrothermal method, and their crystal structures and electrical properties were investigated.Film thickness increased with deposition time and reached 6 µm in 10 h. High-temperature X-ray diffraction measurement showed that successive phase transitions from orthorhombic to tetragonal and from tetragonal to cubic phases take place at 120 and 400 °C, respectively. Microstructure analyses were performed by using electron microscopy, which revealed the existence of two types of stripe patterns with a width of 100 nm or less. In addition, scanning transmission electron microscopy–energy-dispersive X-ray spectroscopy elemental mapping showed that Nb/(Nb + Ta) ratio of the deposited films abruptly changed around 700 nm in thickness. Annealing at 500 °C led to the reduction in leakage current density from 102 to 10–5 A/cm2 at 30 kV/cm, showing that annealing is an effective way to improve insulation. Relative dielectric constant (εr) decreased linearly with increasing frequency, reaching 450 at 10 kHz. Polarization–electric field hysteresis loop and field-induced stain curve were measured by piezoelectric force microscopy, which showed remanent polarization (Pr) of 30 µC/cm2 and piezoelectric constant (d33,PFM) of 70 pm/V. These results demonstrate that (K,Na)(Nb,Ta)O3 thick films with superior electrical properties can be fabricated by the low-temperature deposition technique.

Original languageEnglish
Pages (from-to)8829-8842
Number of pages14
JournalJournal of Materials Science
Issue number21
Publication statusPublished - 1 Jul 2020
Externally publishedYes


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