a- and b-axis-oriented (Bi3.25Nd0.75− x Eu x )Ti3O12 (BNEuT, x = 0–0.75) films of 3.0 µm thickness were fabricated on conductive Nb:TiO2(101) substrates containing 0.79 mass % Nb by high-temperature sputtering at 650 °C, and their structural and piezoelectric characteristics were investigated. The room-temperature remanent polarization (2P r) and effective piezoelectric coefficient (d 33) values for the BNEuT films exhibited maxima of 87 µC/cm2 and 15 pm/V, respectively, at x = 0.10, which were approximately 1.3 times larger than those (2P r = 65 µC/cm2 and d 33 = 12 pm/V) of the nondoped (Bi3.25Nd0.75)Ti3O12 (BNT) nanoplate. The BNEuT film with x = 0.10 had a high a-axis orientation judging from the X-ray diffraction measurement and the observation of the phase image by piezoresponse force microscopy. It is shown that adequate Eu3+ doping of BNT nanoplates produces a larger displacement magnitude of the octahedra than that in the nondoped BNT nanoplate, resulting in an improvement of piezoelectric properties in addition to the ferroelectricity.

a- and b-axis-oriented (Bi3.25Nd0.75 - x Eu x )Ti3O12 (BNEuT, x = 0–0.75) films of 3.0 µm thickness were fabricated on conductive Nb:TiO2(101) substrates containing 0.79 mass % Nb by high-temperature sputtering at 650 °C, and their structural and ferroelectric characteristics were investigated. All the films had a mostly single-phase orthorhombic structure, with high degrees of a- and b-axis orientations of 99.0–99.8%. The lattice parameters (a-, b-, and c-axis lengths) and the calculated orthorhombic lattice distortion decreased monotonically with increasing Eu content. The microstructure of BNEuT films with x = 0–0.50 was nanoplate-like, whereas that of films with x≥0.60 was significantly more bulk-like. The real room-temperature remanent polarization (2P r *), taking the porosity between the nanoplates into account, had a maximum value of 2P r * = 87 µC/cm2 at x = 0.10, which was approximately 1.3 times larger than that (65 µC/cm2) of the nondoped BNT film. It is shown that lattice distortion caused by rotation of octahedra in the a–b plane due to the Eu substitution plays a significant role in the improvement of ferroelectricity.

Sr 2 Bi 4 Ti 5 O 18 (SBTO) films with a-and b-axis orientations, and thicknesses of 0.9-1.2 µm were sputter-deposited on conductive Nb:TiO 2 (101) substrates containing 0.79 mass % Nb. The deposition temperature was varied from 575 to 700 °C under a fixed gas pressure of 0.4 Pa, and the structural and ferroelectric characteristics of the films were investigated. SBTO films deposited at 625-700 °C had a mostly single-phase orthorhombic structure, with a high degree of a-and b-axis orientations [α (h00)/(0k0) ] of 99.0-99.8%. In addition, the full width at half maximum of the (200) diffraction peak was 0.69-0.86°, which indicated good crystallinity. SBTO films deposited at 625-650 °C had a nanoplate-like microstructure with the plates aligned along the [010] direction. The real room-temperature remanent polarization ð2P Ã r Þ, taking the porosity between the nanoplates into account, exhibited a maximum of 40 µC/cm 2 at 650 °C. Thus, the optimal deposition temperature for heteroepitaxial growth of SBTO nanoplates with a high α (h00)/(0k0) of ;99.0% and excellent ferroelectric properties on conductive Nb:TiO 2 substrates is 650 °C under a gas pressure of 0.4 Pa.