Characterization of (Bi_3.25Nd_0.75)Ti₃O₁₂ Thin Films with a- and b-Axis Orientations Deposited on Nb:TiO₂ Substrates by High-Temperature Sputtering

Abstract

a- and b-axis-oriented (Bi3.25Nd0.75)Ti3O12 (BNT-0.75) films, 3.0 µm thick, were fabricated on conductive Nb:TiO2(101) substrates with 0.001–0.79 mass % Nb at 650 °C by high-temperature sputtering. All the films had a mostly single-phase orthorhombic structure and a- and b-axis orientations. The degree of a- and b-axis orientations was high, with values of ≥96%. BNT-0.75 films grown heteroepitaxially on Nb:TiO2(101) substrates containing 0.79 mass % Nb were comprised of nanoplate-like crystals and exhibited the best hysteresis loop shapes, with a remanent polarization (2P r) of 29 µC/cm2 and a coercive field (2E c) of 297 kV/cm.

Effects of post-annealing temperature and micropillar shape on physical properties of micropillar-type multiferroic composite thin films

“…This may be explained as follows. The CFO layer (CFO = 8.5 × 10 −6 °C−1 ) 29) is subjected to stress from the ferroelectric pillar layer (BIT-a-axis = 4.7 × 10 −6 °C−1 , BIT-b-axis = 12.3 × 10 −6 °C−1 , and BIT-c-axis = 17.5 × 10 −6 °C−1 ) 30) due to the difference in the coefficient of linear expansion. Naturally, the degree of stress changes as the annealing temperature changes, and the magnetostriction behavior of the CFO thin-film layer is assumed to have been affected by the change.…”

Effects of deposition temperature on characteristics of ferroelectric Sr2Bi4Ti5O18nanoplates fabricated by RF sputtering

“…The degree of aand b-axis orientations ¡ (h00)/(0k0) was calculated by a method similar to that previously reported for the aand b-axis orientations. [7][8][9][10][11] To determine the out-of-plane and inplane lattice parameters (a, b, and c), XRD reciprocal space mapping (XRD-RSM) measurements were carried out in a high-resolution XRD system (Rigaku SmartLab) using Cu K¡ radiation. Componential (Bi content) analyses and surface microstructural observations of the films were performed using a field-emission scanning electron microscopy (FE-SEM; JEOL JSM-7001FA) system equipped with an energy dispersive X-ray spectrometer (EDS).…”

“…In recent years, lead-free bismuth layer-structured ferroelectrics (BLSFs) [1][2][3][4] have attracted much attention as promising alternatives to lead zirconium titanate (PZT) 5,6) for ferro-and piezoelectric device applications. In previous studies, we succeeded in achieving heteroepitaxial growth of (Bi 3.25 Nd 0.75 )Ti 3 O 12 (BNT) nanoplates with strong aand baxis orientations, [7][8][9] and (Bi 3.25 Nd 0.75¹x Eu x )Ti 3 O 12 (BNEuT, x = 0-0.075) nanoplates with a strong a-axis orientation, 10,11) by high-temperature sputtering using conductive singlecrystal Nb:TiO 2 (101) substrates with 0.79 mass % Nb. Moreover, high-resolution cross-sectional transmission electron microscopy (TEM) images showed that for a BNEuT epitaxial layer with x = 0.10, good long-range lattice matching was achieved between the BNEuT unit cell and seven lattice units of the underlying Nb:TiO 2 substrate.…”

“…As for the relation between the m number and the major polarization of the BLSF compounds, it is known that when m is an odd number greater than 3, significant macroscopic polarization due to ionic displacement appears along the a-axis direction, which is the major polarization axis. 12) We have previously reported the results of studies on the growth of epitaxial films with a high a-axis orientation, and the formation of a nanoplate structure, for BLSFs such as BNT [7][8][9] and BNEuT 10,11) with m = 3. BLSF compounds with m = 5, represented by the general formula A 2 Bi 4 Ti 5 O 18 (ABTO, A = Ba, Sr, and Ca), which consist of stacked (Bi 2 O 2 ) 2+ and (A 2 Bi 2 Ti 5 O 16 ) 2¹ layers, have received considerable attention because of their high potential for use in ferroelectric, piezoelectric, and multiferroic applications.…”

Lattice distortions and piezoelectric properties in (Bi3.25Nd0.75− xEux)Ti3O12 nanoplates with a- and b-axis orientations

“…In recent years, Bi 4 Ti 3 O 12 (BIT), 1,2) SrBi 2 Ta 2 O 9 (SBT), [3][4][5] and (Bi,Nd) 4 Ti 3 O 12 (BNT), [6][7][8][9] which are members of the bismuth layer-structured ferroelectric (BLSF) family, have attracted much attention as promising alternatives to lead zirconate (PZT) 10,11) because they are lead-free and have a low environmental load and excellent ferro-and piezoelectric functionalities. In our previous studies, 12,13) we succeeded in fabricating heteroepitaxially grown (Bi 3.25 Nd 0.75 )Ti 3 O 12 (BNT-0.75) nanoplates with aand b-axis orientations by high-temperature sputtering using conductive Nb:TiO 2 (101) substrates with 0.79 mass % Nb. The formation of the nanoplate structure has made possible by controlling the difference in linear expansion coefficient and the long-range lattice matching between the BNT film and the Nb:TiO 2 (101) substrate.…”