Room temperature electromechanical and magnetic investigations of ferroelectric Aurivillius phase Bi5Ti3(FexMn1−x)O15 (x = 1 and 0.7) chemical solution deposited thin films

Abstract

Aurivillius phase thin films of Bi5Ti3(FexMn1−x)O15 with x = 1 (Bi5Ti3FeO15) and 0.7 (Bi5Ti3Fe0.7Mn0.3O15) on SiO2-Si(100) and Pt/Ti/SiO2-Si substrates were fabricated by chemical solution deposition. The method was optimized in order to suppress formation of pyrochlore phase Bi2Ti2O7 and improve crystallinity. The structuralproperties of the films were examined by x-ray diffraction, scanning electron microscopy, and atomic force microscopy. Optimum crystallinity and pyrochlore phase suppression was achieved by the addition of 15 to 25 mol. % excess bismuth to the sols. Based on this study, 17.5 mol. % excess bismuth was used in the preparation of Bi2Ti2O7-free films of Bi5Ti3FeO15 on SrTiO3(100) and NdGaO3(001) substrates, confirming the suppression of pyrochlore phase using this excess of bismuth. Thirty percent of the Fe3+ ions in Bi5Ti3FeO15 was substituted with Mn3+ ions to form Bi2Ti2O7-free thin films of Bi5Ti3Fe0.7Mn0.3O15 on Pt/Ti/SiO2-Si, SiO2-Si(100), SrTiO3(100), and NdGaO3(001) substrates. Bi5Ti3FeO15 and Bi5Ti3Fe0.7Mn0.3O15thin films on Pt/Ti/SiO2-Si and SiO2-Si(100) substrates were achieved with a higher degree of a-axis orientation compared with the films on SrTiO3(100) and NdGaO3(001) substrates. Room temperature electromechanical and magnetic properties of the thin films were investigated in order to assess the potential of these materials for piezoelectric,ferroelectric, and multiferroic applications. Vertical piezoresponse force microscopy measurements of the films demonstrate that Bi5Ti3FeO15 and Bi5Ti3Fe0.7Mn0.3O15thin films are piezoelectric at room temperature. Room temperature switching spectroscopy-piezoresponse force microscopy measurements in the presence and absence of an applied bias demonstrate local ferroelectric switching behaviour (180°) in the films. Superconducting quantum interference device magnetometry measurements do not show any room temperature ferromagnetic hysteresis down to an upper detection limit of 2.53 × 10−3 emu; and it is concluded, therefore, that such films are not mutiferroic at room temperature. Piezoresponse force microscopy lithography images of Bi5Ti3Fe0.7Mn0.3O15thin films are presented

The effect of Mn doping contents on the structural, dielectric and magnetic properties of multiferroic Bi5Ti3FeO15 Aurivillius ceramics

“…Note here, when Mn doping content is 0.6, many experiments were tried to synthesize pure Mn-doped BTFO compound by adjusting the sintering factors but we failed. However, when the Mn doping content is equal or less than 0.5, all powder diffraction peaks of these BTMFO samples can be indexed by JCPDF 82-0063, which is in accordance with four-layer Aurivillius BTFO phase, and also consistent with those of BTFO ceramics in other literatures [3][4][5][6]. The results indicated that Mn-doped BTFO compounds with Aurivillius phase can be obtained when the Mn-doping content is less than 0.5, while impurities appear obviously even in the XRD limit of precision when Mn-doping content x is beyond 0.5.…”

“…Single-phase multiferroic materials with Aurivillius structure of the general formula Bi 4 Bi n À 3 Ti 3 Fe n À 3 O 3n þ 3 (n Z 4) have been widely studied in recent years because of the coexistence of ferroelectric order and magnetic order [1][2][3][4][5][6][7][8], and especially the associated electric/magnetic polarization coupling between the two different orders [9][10][11]. This could drive Aurivillius family to be qualified in new application fields, such as magnetic sensors, multi-state storages and spintronics and so on, besides ferroelectric random access memory (FeRAM) and piezoelectric actuators.…”

“…Four-layer Bi 5 Ti 3 FeO 15 (BTFO, n=4) is a typical member of Aurivillius multiferroic family, composed of a four-layer pseudo perovskite (Bi 3 Ti 3 FeO 13 ) 2 À sandwiched by two layers of fluorite-like (Bi 2 O 2 ) 2 þ structure along c axis. Structural, electric, magnetic, optical, magnetoelectric (ME) properties and electronic structure of BTFO compound with ceramic and film forms have been widely investigated [1][2][3][4][5][6][7][8]. Ferroelectric Curie temperature (T c ) was determined to be about 730 1C along with space group transition from A2 1 am to I4/mmm [12].…”

Room temperature ferroelectric and magnetic investigations and detailed phase analysis of Aurivillius phase Bi5Ti3Fe0.7Co0.3O15 thin films

“…In this study, we report the first magnetic investigations of Bi 5 19 The films were spin-coated on a-quartz substrates (42.75 6 15'ST-Cut) by a commercial spinner (spin coater KW-4A, Chemat Technology) operating at 4500 rpm for 30 s. Quartz substrates (350 lm thick) were chosen for their low diamagnetic contribution. Excess solvents and residual organics were removed from the films by baking on a calibrated hot plate at 300 6 5 C for approximately 10 min.…”

A study of the temperature dependence of the local ferroelectric properties of c-axis oriented Bi6Ti3Fe2O18 Aurivillius phase thin films: Illustrating the potential of a novel lead-free perovskite material for high density memory applications

“…22,35 Ferroelectric polarization in these materials is strongly hindered by additional impurity phases (such as pyrochlore). 23 These microstructural defects can be overcome by using optimised growth processes. For instance, the deposition of highly textured, oriented and uniform thin films can in principle extensively improve desired physical properties such as ferroelectric polarization, in material systems where the polarization is dependent on crystal orientation.…”