Evolution of structural transition,grain growth inhibition and collinear antiferromagnetism in (Bi1-xSmx)FeO3 (x = 0 to 0.3) and their effects on dielectric and magnetic properties

Structural phase transition from rhombohedral (space group: R3c) to orthorhombic (space group: Pnma) cell is observed in Bi_1-xSm_xFeO₃ (x = 0 – 0.3) compounds. The evolution of non-ferroelectric Pnma phase reduces the dielectric strength and stabilizes the collinear antiferromagnetism. Temperature variations of dielectric permittivity and its loss component show the presence of Polomska transition and it is found to shift downward towards room temperature with increase in Sm concentration. The frequency dispersion of complex dielectric permittivity was best explained in terms of Havriliak-Negami equation and by invoking the conductivity contribution. The Cole-Cole plots of complex dielectric permittivity show two distinct semicircular arcs corresponding to dielectric relaxation due to grains and grain boundaries respectively. The relaxation dynamics is explained in terms of polaron hopping across Fe²⁺ and Fe³⁺ sites in grains and short range movement of oxygen vacancies at grain boundaries. The composition dependence of magnetization is explained in terms of evolution of weak ferromagnetism due to partial breaking of spiral spin structure and the growth of collinear antiferromagnetism driven by Pnma phase. We have also observed the exchange bias behavior in some of Sm substituted samples due to the exchange interaction at the interface of coexisting weak ferromagnetic (R3c) and collinear antiferromagnetic (Pnma) phases.     

Micro‐to‐nano domain structure and orbital hybridization in rare‐earth‐doped BiFeO3 across morphotropic phase boundary

This work demonstrates the critical role of orbital hybridizations in the FeO₆ octahedral distortion, composition‐driven phase transition, and bonding covalency in multiferroic (Bi_1?xSm_x)FeO₃ (x = 0.10‐0.20) ceramics in the vicinity of the morphotropic phase boundary (MPB). Sequential composition‐driven transitions from the polar rhombohedral R3c to antipolar orthorhombic Pbam and then Pnma phases were revealed as the system crosses the MPB with increasing Sm. A coexistence of ferroelectric (FE) rhombohedral R3c and antiferroelectric (AFE) PbZrO₃‐like orthorhombic Pbam symmetries was identified by the 1/2{000}, 1/4{100}, 1/4{110}, 1/4{111}, and 1/4{121} superlattice diffractions at x = 0.12‐0.16. In addition to R3c and Pbam space groups, the nonpolar SmFeO₃‐like orthorhombic Pnma space group becomes the predominant phase at x = 0.20 confirmed by the 1/2{100} superlattice diffractions. The Fe L₃‐edge and oxygen K‐edge synchrotron X‐ray absorptions indicate that the O 2p–Fe 3d and O 2p–Bi 6s/6p orbital hybridizations were decreased as the system approaches the MPB.     

Correlation between structural,ferroelectric, piezoelectric and dielectric properties of Ba0.7Ca0.3TiO3-xBaTi0.8Zr0.2O3 (x = 0.45, 0.55) ceramics

We report on the correlation between structural, ferroelectric, piezoelectric and dielectric properties of the (1-x)Ba_0.7Ca_0.3TiO₃-xBaTi_0.8Zr_0.2O₃ (x?=?0.45, 0.55; abbreviated as 55BCT30 and 45BCT30) ceramics close to morphotropic phase boundary (MPB) region. The 55BCT30 and 45BCT30 ceramics were synthesized by the standard, high-temperature solid state ceramic method. X-ray diffraction (XRD) along with Rietveld refinement indicate that the 55BCT30 ceramics exhibit rhombohedral (R, space group R3m), orthorhombic (O, space group Amm2) and tetragonal (T, space group P4mm) phases while 45BCT30 ceramics exhibit only T and O phases. The temperature dependent Raman spectroscopy measurements confirm the structure and phase transformations observed from XRD. All the ceramics are chemically homogeneous and exhibit a dense microstructure with a grain size of 5–7?µm. The presence of polarization-electric field and strain-electric field hysteresis loops confirm the ferroelectric and piezoelectric nature of the ceramics. The polarization current density-electric field curves show the presence of two sharp peaks in opposite directions indicating the presence of two stable states with opposite polarity. Higher values of direct piezoelectric coefficient (d₃₃ ~?360 pC/N) were observed due to the existence of low energy barrier near MPB region and polymorphism. The 55BCT30 ceramics exhibit a higher value of electrostrictive coefficient (Q₃₃ ~?0.1339?m⁴/C²) compared to the well-known lead-based materials. The temperature dependent dielectric measurements indicate the O to T phase transition for 55BCT30 and 45BCT30. These ceramics exhibit a Curie temperature (T_c) of 380?K with a dielectric maximum of ~ 4500.     

Effect of Li addition on phase formation behavior and electrical properties of (K0.5Na0.5)NbO3 lead free ceramics

In this work, Li-modified KNN ceramic compositions ((K_0.5Na_0.5)_1−xLi_x)NbO₃ with x = 0.03, 0.04, 0.05, 0.06, 0.65 and 0.07 were prepared by a conventional solid-state mixed-oxide method. The structural phase formation and microstructure were characterized by X-ray diffraction technique (XRD) and scanning electron microscopy (SEM). It has been found that a morphotropic phase boundary (MPB) between orthorhombic phase and tetragonal phases should exist between compositions with Li contents of 6-6.5%. The Curie temperature (T_c) of the ceramics shifted to higher temperature with increasing Li content. The room temperature dielectric constant was also seen to be higher than the pure KNN ceramics. In addition, the ferroelectric properties were found to enhance at near MPB compositions. This study clearly showed that the addition of Li could improve the dielectric and ferroelectric properties in (K_0.5Na_0.5)NbO₃ ceramics.     

Structural and Electrical Characteristics of (1−x)Pb(Lu1/2Nb1/2)O3–xPbTiO3 Ceramics with Low PbTiO3

A solid solution of (1?x)Pb(Lu_1/2Nb_1/2)O₃–xPbTiO₃ with composition of 0.01 ≤ x ≤ 0.08 have been prepared successfully. XRD analysis indicates the crystal structure adopts an orthorhombic (O) phase in 0.01 ≤ x ≤ 0.06 interval and becomes the coexistence of O and rhombohedral (R) phase at x = 0.07, then turns into R phase mostly at x = 0.08. In addition, two sets of superlattice reflections due to B‐site ordering and antiparallel cation displacement are distinguished by XRD and the superstructures which arise from antiparallel cation displacement disappear gradually with the increasing x. The grain size increases gradually with the increasing x, and then becomes the bimodal microstructure at x ≥ 0.06 due to the coexistence of O and R phase. The dielectric spectra exhibit Curie temperature decreases from 248°C to 147°C with increasing x from 0.01 to 0.08. As 0.01 ≤ x ≤ 0.04, the samples display typical double hysteresis loops, suggesting antiferroelectric nature, then turn into ferroelectric gradually at x = 0.05. Finally, it exhibit typical ferroelectric hysteresis loops in 0.06 ≤ x ≤ 0.08 interval.     

Improved ferroelectric properties of BiFeO3-based piezoelectric ceramics through morphotropic phase boundary construction

The ceramic (1-x)BiFe_0.985Sc_0.015O₃-xBaZr_0.2Ti_0.8O₃ + 1mol% MnO₂ (x = 0.20, 0.25, 0.30, 0.35) (BFS-xBZT) was synthesized using the traditional ceramic sintering method. The components of the ceramic were determined by constructing a morphotropic phase boundary (MPB) which consists of rhombohedral (R) and tetragonal (T) phases (0.24≤ x ≤ 0.26). With the accumulation of BZT content, relax behaviors were observed by dielectric properties measurements. At the MPB, the crystal structures of the R phase and T phase change abruptly. The distortion degree of the R phase increases, and the differences between a and c of the T phase decrease. An enhanced ferroelectricity Pr of ~27.8 μC/cm² and apex piezoelectric coefficient d₃₃ of 131 ± 4 pC/N are obtained near the MPB (x = 0.25), due to the R-T phase coexistence near room temperature. The results show that BFS-xBZT ceramics could be a candidate for lead-free piezoelectric ceramics at high operating temperatures.     

Phase evolution and electrical behaviour of samarium-substituted bismuth ferrite ceramics

Bi_1-xSm_xFeO₃ (x?=?0.15–0.18) ceramics with high density were produced using spark plasma sintering. The effects of composition, synthesis conditions and temperature on the phase evolution were studied, using XRD, TEM and dielectric spectroscopy. The coexistence of the ferroelectric R3c, antiferroelectric Pnam and paraelectric Pnma phases was revealed, with relative phase fractions affected by both calcination conditions and Sm concentration. Experiments on powdered samples calcined at different temperatures up to 950?°C suggest higher calcination temperatures promote Sm diffusion, allowing samples to reach compositional homogeneity. The structural transitions from the Pnam and R3c phases to the Pnma phase were comprehensively investigated, with phase transition temperatures clearly identified. The dielectric permittivity, electrical resistivity and breakdown strength were increased upon Sm-substitution, while ferroelectric switching was suppressed. The polarization-electric field loop became increasingly narrow with increasing Sm-content, but double hysteresis loops, which may reflect a reversible antiferroelectric to ferroelectric transformation, were not observed.     

Phase formation,electrical properties and morphotropic phase boundary of 0.95Pb(ZrxTi1−x)O3–0.05Pb(Mn1/3Nb2/3)O3 ceramics

Ferroelectric ceramics in specific composition of 0.95Pb(Zr_xTi_1?x)O₃–0.05Pb(Mn_1/3Nb_2/3)O₃ or PZT–PMnN (with x=0.46, 0.48, 0.50, 0.52, and 0.54) have been investigated in order to identify the morphotropic phase boundary (MPB) composition. The effects of Zr/Ti ratio on phase formation, dielectric and ferroelectric properties of the specimens have also been investigated and discussed. X-ray diffraction patterns indicate that the MPB of the tetragonal and rhombohedral phase lies in x=0.52. The crystal structure of PZT–PMnN appeared to change gradually from tetragonal to rhombohedral phase with increasing Zr content. The dielectric and ferroelectric properties measurements also show a maximum value (ε_r, tan δ and P_r) at Zr/Ti=52/48, while the transition temperature decreases with increasing Zr content.     

The effect of morphotropic phase boundary on dielectric properties of Bi0.5Na0.5Ti1−xZrxO3 solid solutions

Lead-free bismuth sodium titanate zirconate (Bi_0.5Na_0.5Ti_1?xZr_xO₃ or BNTZ) solid solutions with varied composition of x=0.50, 0.55, 0.58, 0.60, 0.63, 0.65, 0.68, 0.70, 0.73, 0.75 and 0.78 mol fraction were obtained using a conventional mixed-oxide method. XRD analysis indicated that the increase in concentration of Zr led to compositions across morphotropic phase boundary region. A quantitative structural investigation was carried out using the X-ray powder diffraction data. The rhombohedral phase was found to dominate for x<0.68 with space group R3c. In the morphotropic phase boundary (MPB) region i.e. 0.68≤x≤0.75, it was demonstrated that coexistence of rhombohedral and orthorhombic phase was observed. For x=0.78, the phase was completely orthorhombic with space group Pmna. Furthermore, the dielectric properties showed some enhanced activity of dipole movement at MPB boundaries which supported the presence of MPB region in this material system.     

Synthesis and characterizations of KNN ferroelectric ceramics near 50/50 MPB

Lead free ferroelectric ceramics near the morphotropic phase boundary (MPB) of K_xNa_1?x(NbO₃)/KNN system (where x=0.48, 0.50, 0.52) were synthesized in the single perovskite phase by the partial co-precipitation synthesis route. The compositional dependences of phase, structure and electrical properties were studied in detail. X-ray diffraction (XRD) study revealed the coexistence of orthorhombic and monoclinic structures in K_0.50N_0.50NbO₃. SEM characterization of the sintered KNN ceramics revealed dense and homogeneous packing of grains. Room temperature (RT) dielectric constant (ε_r) ～648, dielectric loss (tan δ) ～0.05 at 100 kHz, a relatively high density (ρ) ～4.49 g/cm³, remnant polarization (P_r) ～11.76 μC/cm², coercive field (E_c) ～9.81 kV/cm, Curie temperature (T_c) ～372 °C and piezoelectric coefficient (d₃₃) ～71 pC/N observed in K_0.50N_0.50NbO₃ suggested that it can be an important lead free ferroelectric material.     

Optimized electric-energy storage in BiFeO3–BaTiO3 ceramics via tailoring microstructure and nanocluster

This study demonstrates the high energy-storage performance using 0.1 wt% MnO₂–added 0.7(Bi_1?xSm_xFeO₃)? 0.3(BaTiO₃) (x = 0–0.3) ceramics through tailoring microstructures and polar order. Sequential structure transitions were identified from a co-occurrence of nonpolar pseudo-cubic Pm-3m and ferroelectric rhombohedral R3c symmetries to antipolar orthorhombic Pbam and nonpolar orthorhombic Pnma symmetries as Sm substitution increases. Recoverable energy densities (W_rec) of 4.5 J/cm³ and 4.1 J/cm³ with efficiencies (η) of 62.1% and 78.1% were achieved respectively for x = 0.15 and 0.2 at a field of 220 kV/cm. The improved energy storage is associated with microstructure modification and complex grain matrix, consisting of grain boundaries, nanocluster/nanomosaic structures, core-shell structures, and polar nanoregions. The nanocluster/nanomosaic structures may act as barriers to suppress polar order and enhance dielectric breakdown strength. This work provides an efficient route to utilize binary BiFeO₃-BaTiO₃ ceramics for electrical energy storage.     

Synthesis,structure and dielectric properties of (1−x)[0.9BiFeO3–0.1DyFeO3]–xPbTiO3 pseudo-binary ceramics

In order to develop multiferroics with large magnetization and polarization, we have prepared a series of (1?x)[0.9BiFeO₃–0.1DyFeO₃]–xPbTiO₃ [BDF–xPT] solid solution ceramics by solid state reaction. X-ray diffraction reveals that, with the increase of PbTiO₃ concentration, the solid solution transforms from a rhombohedral to a tetragonal phase with the presence of a morphotropic phase boundary (MPB) region located at 0.28≤x≤0.40 at room temperature, in which the rhombohedral, tetragonal and orthorhombic phases coexist. The temperature dependence of the dielectric permittivity indicates that the Curie temperature decreases with the increasing amount of PbTiO₃. Based upon the structural analysis and dielectric characterization, a preliminary phase diagram for the BDF?xPT pseudo-binary system has been proposed. It is found that the ceramics of compositions around the MPB exhibits much better dielectric properties with dielectric constant of the BDF–0.37PT ceramics reaching 459 at 1 kHz, confirming the beneficial effects of the MPB on the dielectric performance.     

Enhanced ferroelectric,magnetic and magnetoelectric properties of multiferroic BiFeO3–BaTiO3–LaFeO3 ceramics

A lead–free multiferroic ceramic 0.7BiFeO₃–0.3BaTiO₃ showed strong ferroelectric and piezoelectric properties, but weak magnetic and magnetoelectric properties. We herein expected that the electrical and magnetic properties of 0.7BiFeO₃–0.3BaTiO₃ ceramics could be enhanced by introducing LaFeO₃. (0.7–x) BiFeO₃–0.3BaTiO₃–xLaFeO₃ (x?=?0–0.2) were synthesized by solid-state reaction. All the ceramics formed a perovskite structure, and a morphotropic phase boundary (MPB) between rhombohedral and orthorhombic phases formed at x?=?0.025. The ceramics with MPB composition had high unipolar strain (S_max = 0.14%), piezoelectricity (d₃₃ = 223 pC/N, d₃₃ * = 350?pm/V), ferroelectricity (P_r = 25.67 mC/cm²) and magnetoelectricity (a_ME = 466.6?mV/cm·Oe), which can be attributed to addition of La ions. The improved phase angle also demonstrated augmentation of ferroelectricity on the microscopic view. The ferromagnetism was evidently improved after LaFeO₃ doping, and the remanent magnetization M_r increased from 0.0207 to 0.0622?emu/g with rising x from 0 to 0.075. In conclusion, with strong magnetoelectric properties, the prepared ceramics may be applicable as promising lead–free multiferroic ceramic materials for novel electronic devices.     

Structural phase transition,electrical and photoluminescent properties of Pr3+-doped (1-x)Na0.5Bi0.5TiO3-xSrTiO3 lead-free ferroelectric thin films

Lead-free ferroelectric Pr³⁺-doped (1-x)Na_0.5Bi_0.5TiO₃-xSrTiO₃ (x?=?0–0.5) (hereafter abbreviated as Pr-NBT-xSTO) thin films were prepared on Pt/Ti/SiO₂/Si and fused silica substrates by a chemical solution deposition method combined with a rapid thermal annealing process at 700?°C, and their structural phase transition, dielectric, ferroelectric, and photoluminescent properties were investigated as a function of STO content. Raman analysis shows that with increasing STO content, the phase structures evolve from rhombohedral phase to coexistence of rhombohedral and tetragonal phases (i.e. morphotropic phase boundary), and then to tetragonal phase. The structural phase transition behavior has been well confirmed by temperature- and frequency- dependent dielectric measurements. Meanwhile, the variation in photoluminescence intensity of Pr³⁺ ions with different STO content in the NBT-xSTO thin films also indicates that there exists a clear structural phase transition when the film composition is close to the morphotropic phase boundary. Superior dielectric and ferroelectric properties are obtained in the Pr-NBT-0.24STO thin films due to the formation of morphotropic phase boundary. Our study suggests that Pr-NBT-xSTO thin films be promising multifunctional materials for optoelectronic device applications.     

Morphotropic phase boundary,polymorphic phases and enhanced electrostrain/piezoelectricity in Ag1-xKxNbO3 solid-solution ceramics

Ag_1−xK_xNbO₃(AKNx (x ≤ 0.12) ceramics were prepared to understand the relationship of structure-properties driven by compositions and temperatures. The results suggested that this binary system possessed a morphotropic phase boundary (MPB) consisted of ferrielectric and ferroelectric phases with iso-symmetry at room temperature, in which domains switching together with electric-field-induced irreversible phase transition achieved a much higher electrostrain (S_max = 0.4%) than other compositions. But this MPB was destroyed after poling, leading to inferior piezoelectricity. A phase diagram was drawn after analyzing in situ XRD and dielectric data, where an almost vertical ferrielectric/antiferroelectric ↔ polymorphic ferroelectric MPB line starting from a triple point was proposed. As temperature increased, the piezoelectricity significant enhanced near ferroelectric orthorhombic ↔ monoclinic phase boundary, while the highest piezoelectricity was achieved near the monoclinic ↔ paraelectric phase boundary with d₃₃ = 200 pC/N. The enhanced piezoelectricity is intimately related to the ferroelectric monoclinic possessing Pm symmetry.     

Effect of (Zn,Mn) co-doping on the structure and ferroelectric properties of BiFeO3 thin films

BiFe_1-2xZn_xMn_xO₃ (BFZMO, with x = 0–0.05) thin films were synthesized via sol–gel method. Effects of (Zn, Mn) co-doping on the structure, ferroelectric, dielectric, and optical properties of BiFeO₃ (BFO) films were investigated. BFZMO thin films exhibit rhombohedral structure. Scanning electron microscopy (SEM) images indicate that co-doping leads to a decrease in grain size and number of defects. Leakage current density (4.60 × 10^?6 A/cm²) of BFZMO film with x = 0.02 was found to be two orders of magnitude lower than that of pristine BFO film. Owing to decreased leakage current density, saturated P–E curves were obtained. Maximum double remnant polarization of 413.2 μC/cm² was observed for BFZMO thin film with x = 0.02, while that for the BFO film was found to be 199.68 μC/cm². The reason for improved ferroelectric properties is partial substitution of Fe ions with Zn and Mn ions, which resulted in a reduction in the effect of oxygen vacancy defects. In addition, co-doping was found to decrease optical bandgap of BFO film, opening several possible routes for novel applications of these (Zn, Mn) co-doped BFO thin films.     

Ferroelectric and magnetic properties in (1−x)BiFeO3–x(0.5CaTiO3–0.5SmFeO3) ceramics

Multiferroic ceramics were prepared and characterized in (1?x)BiFeO₃–x(0.5CaTiO₃–0.5SmFeO₃) system by a standard solid‐state reaction process. The structure evolution was investigated by X‐ray diffraction and Raman spectrum analyses. The refinement results confirmed the different phase assemblages with varying amounts of polar rhombohedral R3c and nonpolar orthorhombic Pbnm as a function of the substitution content. In the compositions range of 0.2≤x≤0.5, polar R3c and nonpolar Pbnm coexisted, which was referred to polar‐to‐nonpolar morphotropic phase boundary (MPB). According to the dielectric and DSC analysis results, the ceramics with x≤0.2 changed to diffused ferroelectric, and the ferroelectric properties were enhanced significantly. Two dielectric relaxations were detected in the temperature range of 200‐300 K and 500‐700 K, respectively. The high‐temperature dielectric relaxation was attributed to the grain‐boundary effects. While the low temperature dielectric relaxation obtained in the samples with x=0.3‐0.5 was related to the charge transfer between Fe²⁺ and Fe³⁺. The magnetic hysteresis loops measured at different temperature indicated the enhanced magnetic properties in the present ceramics, which could be attributed to the suppressed cycloidal spin magnetic structure by Ti ions. In addition, the rare‐earth Sm spin moments might also affect the magnetic properties at relatively lower temperature.     

Large strain of temperature insensitive in (1–x)(0.94Bi0.5Na0.5TiO3–0.06BaTiO3) –xSr0.7La0.2TiO3 lead-free ceramics

Novel (1–x)(0.94Bi_0.5Na_0.5TiO₃–0.06BaTiO₃)–xSr_0.7La_0.2TiO₃ ternary lead-free ceramics (BNBT–xSL, x?=?0.00–0.08) were fabricated by the widely used solid-state sintering technique. The crystal phase, microstructure, dielectric relaxation, piezoelectric, and electromechanical properties of each composition were systematically analyzed. It is found that the addition of SL has little effect on the crystal phase and grain morphology, but it can remarkably improved the relaxation property of the ceramic sample and gave rise to favourable dielectric properties in a wide range of temperatures. In addition, as the SL content increases, the ferroelectric to relaxor temperature (T_F-R) is adjusted to below ambient temperature. More importantly, the decay of ferroelectric phase resulted in a significant increase in strain value: the large strain of 0.5% with normalized strain of 625?pm/V was obtained at 80kv/cm and x?=?0.04. Finally, the composition exhibited high strain of temperature insensitivity range from room temperature to 100?°C, the strain value remained above 0.4% and kept within 5%. The results are due to the coexistence of rhombohedral polar-nanoregions (PNRs) and tetragonal PNRs during the relaxor region. This result is of great importance to the developments of temperature-insensitive strain sensors and actuators.     

Ultra-high strain responses in lead-free (Bi0.5Na0.5)TiO3-BaTiO3-NaNbO3 ferroelectric thin films

Lead-free (Bi_0.5Na_0.5)TiO₃ (BNT)-based piezoelectric materials, have a great potential for high-precision actuators’ applications. In this work, the high-quality (0.94-x%)(Bi_0.5Na_0.5)TiO₃-0.06BaTiO₃-x%NaNbO₃ (x = 2–10, BNT-6BT-xNN) thin films have been successfully deposited on Pt/TiO₂/SiO₂/Si substrates by sol-gel method. An ultra-high poling strain S_pol value of 1.7% with a unipolar strain S_uni value of 1.47% was reported in the BNT-6BT-6NN thin films. The coexistence of the ferroelectric phase and relaxor state was observed in the compositions of x = 2–8. Furthermore, the BNT-6BT-6NN thin films show more active domain switching compared to other compositions. It is demonstrated that the optimized strain responses in the BNT-6BT-6NN are attributed to a synergistic reaction of active domain switching and reversible electric-field-induced phase transition between the ferroelectric phase and relaxor state. Our systematic study demonstrates that the BNT-6BT-xNN thin films with an improved strain response are promising candidates for the applications of miniaturized actuators.     

Investigation of Tb-doping on structural transition and multiferroic properties of BiFeO3 thin films

Pure BiFeO₃ (BFO) and Bi_1−xTb_xFeO₃ (BTFO) thin films were successfully prepared on FTO (fluorine doped tin oxide) substrates by the sol–gel spin-coating method. The effects of Tb-doping on the structural transition, leakage current, and dielectric and multiferroic properties of the BTFO thin films have been investigated systematically. XRD, Rietveld refinement and Raman spectroscopy results clearly reveal that a structural transition occurs from the rhombohedral (R3c:H) to the biphasic structure (R3c:H+R-3m:R) with Tb-doping. The leakage current density of BTFO_x=0.10 thin film is two orders lower than that of the pure BFO, i.e. 5.1×10⁻⁷ A/cm² at 100 kV/cm. Furthermore, the electrical conduction mechanism of the BTFO thin films is dominated by space-charge-limited conduction. The two-phase coexistence of BTFO_x=0.10 gives rise to the superior ferroelectric (2P_r=135.1 μC/cm²) and the enhanced ferromagnetic properties (M_s=6.3 emu/cm³). The optimal performance of the BTFO thin films is mainly attributed to the biphasic structure and the distorted deformation of FeO₆ octahedra.