Saturated Ferroelectric Hysteresis Loops Research Articles

Investigation of structural and enhanced piezoelectric properties in low lead content Na0.5Bi0.5TiO3-BaTiO3-PbTiO3 system

Through this work the authors report the structural, ferroelectric, and piezoelectric properties of PbTiO3 modified ceramics: (1–2x)Na0.5Bi0.5TiO3-xBaTiO3-xPbTiO3: (1–2x)NBT-xBT-xPT with x = 0.01, 0.03, 0.05, 0.07 and 0.09. The X-ray diffraction analysis of (1–2x)NBT-xBT-xPT revealed the existence of monoclinic (M) phase for x = 0.01 and 0.03 with the presence of ½(311) superlattice reflection, which acts as a structural bridge between the Rhombohedral (R) and Tetragonal (T) phases. Phase transition from M to T phase was observed at x = 0.03 which is supported by the presence of (002)/(200) splitting in the diffraction pattern. The measured mean grain size and density for x = 0.03 was 5.7 µm and 5.834 g/cm3 respectively, which was the maximum compared to other compositions. The chemical state of elements in the ternary system is found out using the X-ray photoelectron spectroscopy. A diffuse phase transition is perceived from the temperature dependent dielectric studies for x ≤ 0.03, while this diffusiveness decreases for x > 0.03 with the increase in concentration of substituents. Besides, the ferroelectric (FE) to relaxor (RE) transition, TFR is also diminished in higher concentration of BT and PT. A well saturated ferroelectric hysteresis loop with saturation polarization (Ps) and remnant polarisation (Pr) values of 35 and 32 µC/cm2 respectively is achieved for x = 0.03. Under an applied field of 48 kV/cm, a unipolar strain value of 0.26% is achieved for the same composition with a piezoelectric charge co-efficient (d33*) of 541 pm/V. The superior piezoelectric performance shown by (1–2x)NBT-xBT-xPT with a very low lead content of 3 mol%, which is at the proximity of M-T phase transition is explained using the polarisation rotation mechanism, that occurs in conjunction between polar-polar phases. The flat free energy profile that exists at the phase boundaries, eases the rotation of the polarisation vector and hence the piezoelectric constant. Also, a larger grain size will also relieve the polarisation rotation.

Ferroelectricity of Ca9Fe(PO4)7 and Ca9Mn(PO4)7 ceramics with polar whitlockite-type crystal structure

Ca9Fe(PO4)7 is a member of the double phosphate family having polar whitlockite-type crystal structure. The phase transition from the room temperature polar R3c to the high temperature non-polar R c phase has been called a ferroelectric phase transition using complementary experiments such as temperature dependent second harmonic generation and dielectric constant measurements however no ferroelectric hysteresis measurement has been reported. In order to be able to call these polar materials ferroelectric, measurement of a saturated ferroelectric hysteresis loop is necessary to demonstrate that the electrical polarization of these materials is switchable. In order to realize this goal, we have synthesized Ca9Fe(PO4)7 as well as structurally identical Ca9Mn(PO4)7 using solid state synthesis. Crystal structure of the ceramics were confirmed using Rietveld refinement of the x-ray diffraction (XRD) patterns. Differential scanning calorimetry (DSC) measurements revealed phase transition temperatures of 848 and 860 K for Ca9Fe(PO4)7 and Ca9Mn(PO4)7, respectively. Our ferroelectric hysteresis measurements and current electric field loops (I-E) derived from the hysteresis loops showed that the loops cannot be saturated and the direction of the electrical polarization of both materials cannot be switched up to the largest applied electric field of 100 kV/cm. Possible origins of this behaviour are discussed.

Improved ferroelectric response of pulsed laser deposited BiFeO3-PbTiO3 thin films around morphotropic phase boundary with interfacial PbTiO3 buffer layer

(1 − x)BiFeO3-xPbTiO3 (BF-xPT) is an interesting material for sensing and actuating devices with large polarization near the morphotropic phase boundary (MPB) (x = 0.30) in the bulk form. However, pulsed laser deposition (PLD) grown (BF-xPT) thin films usually show high electrical leakage and, hence, saturated ferroelectric hysteresis loops are only obtained at subzero temperatures. In this article, we report on high room temperature ferroelectric polarization with saturated hysteresis loops in pulsed laser deposited (BF-xPT) polycrystalline thin films of compositions near the MPB with the use of a thin buffer layer of PbTiO3 (PT). The thin films possessed a perovskite structure with excellent crystallinity and exhibit the presence of a monoclinic (Cm) phase (MA-type) for x = 0.20–0.25 and a mixture of a monoclinic (Cm) phase and a tetragonal (P4mm) phase for x = 0.30–0.35 compositions. The thin films with composition x = 0.25 exhibit a monoclinic phase and yield very large room temperature ferroelectric polarization (2Pr > 80μC/cm2), perhaps the highest room temperature ferroelectric polarization and excellent piezoelectric properties in PLD deposited (BF-xPT) thin films of near-MPB composition. Furthermore, the evolution of ferroelectricity with PT content, studied using room temperature Raman spectroscopy, reveals a correlation with lattice dynamics and stereochemical activity of Bi. Piezoforce domain analysis of the thin films reveals that ferroelectric polarization and electrical leakage in the thin films are intricately related to the type of domains present in the samples, viz., 180°, 109°, 90°, and 71° due to differences in the nature of the domain walls.

Ferroelectric polarization tuning the photovoltaic and diode-like effect of the Ni, Sm co-doped BiFeO3 film capacitors

Although BiFeO3-based photovoltaic devices have currently attracted much attention due to their unique physical properties, their practical applications have been limited by the complex and obscure intrinsic physical mechanisms. This paper reported the synthesis of the Ni, Sm co-doped BiFeO3 film capacitors by a spin-coating technology. The results and analysis showed that co-doped BiFeO3 films exhibited low leakage current and well saturated ferroelectric hysteresis loops. Especially, the photovoltaic effect and diode-like effect of ferroelectric film capacitors could be efficiently modulated by the external polarization. The complex intrinsic physical mechanism of photovoltaic effect and diode-like effect under polarization modulation was studied and explained clearly by the energy-band diagram and the theory of ferroelectric polarization. Moreover, the effect of inherent and external factors on photovoltaic output of BiFeO3 films was jointly analyzed by the ferroelectric polarization and photovoltaic mechanism. This theoretical exploration may facilitate to improve the understanding of the photovoltaic effect in ferroelectrics, which will be likely to have the opportunity to advance the design of switchable devices that combine ferroelectric and photovoltaics.

Y3+ doped 0.64PMN-0.36PT ceramic for energy scavenging applications: Excellent piezo-/ferro-response with the investigations of true-remanent polarization and resistive leakage

In this work, the detailed ferroelectric properties of pure and yttrium doped 0.64 Pb(Mg1/3Nb2/3)O3-0.36PbTiO3 (Y-doped PMN-PT) ceramics including determination of true remanent polarization and study of resistive leakage were investigated. In dielectric study, the transition temperature (Tm) for the pure and Y-doped ceramic was found to be 205 °C and 165 °C, respectively. Displacement vs. Voltage (D-V) butterfly loops were traced from which a high value of the piezoelectric coefficient for Y-doped PMN-PT (d33 = 604 pm/V) was revealed which was fairly greater than the observed value for pure PMN-PT (d33 = 547 pm/V). The Y-doped PMN-PT ceramic displayed excellent saturated ferroelectric hysteresis loops with higher values of coercive field (Ec), spontaneous (Ps) and remanent (Pr) polarizations, and pyroelectric coefficient (p) compared to the pure PMN-PT ceramic. Also, the Y-doped PMN-PT ceramic displayed good fatigue resistant characteristic indicating its high ferroelectric quality. The relative values of true remanent polarization i.e. Ptr/Pr (in %) were found to be ∼82.86% and 89.60% for pure and Y-doped PMN-PT, respectively using the “Remanent Hysteresis” Task. Also, the resistive-leakage characteristic of both pure and doped ceramics was analyzed using Time-dependent compensated (TDC) hysteresis task. Finally, both pure and Y-doped PMN-PT ceramics have been used for building piezoelectric energy harvesting devices (PEHDs). The Y-doped PMN-PT ceramic based PEHD showed enhanced performance by generating an output voltage around 60 V under periodic mechanical tapping (∼2.0 kgf @ 5 hz) and thus finds application in powering various self-powered devices.

Ferroelectric Sb-doped PMN-PT crystal: high electromechanical response with true-remanent polarization and resistive leakage analyses

In this work, pure and Sb-doped PMN-PT (64:36) crystals with pure perovskite phase have been successfully grown using high temperature solutions technique (or, flux technique), in the vicinity of MPB with the size of the crystals varying from 2 × 2 × 1 mm3 to 7 × 5 × 4 mm3. Various properties like dielectric, piezoelectric, ferroelectric and pyroelectric were investigated for the Sb-doped PMN-PT crystals and have been compared to that of pure PMN-PT crystals. In the dielectric studies, the Curie temperature (Tc) for the pure and doped crystal was found to be 190 °C and 155 °C, respectively. Butterfly loops were traced from which a high value of the piezoelectric coefficient for Sb-doped crystal (d33* = 1972 pm/V) was revealed in the voltage range 250–500 V which was fairly greater than that observed for pure PMN-PT crystal (d33* = 1413 pm/V). The Sb-doped PMN-PT crystals displayed excellent saturated ferroelectric hysteresis loops with higher remanent polarization (Pr) value compared to the pure PMN-PT crystals. The doped crystals also displayed good fatigue resistant characteristic indicating the high ferroelectric quality of the crystals. The true or usable polarization (Ptr) component was extracted using the “True-remanent hysteresis” task. The value of Ptr was found to be 41.53 µC/cm2 suggesting lesser contributions (~ 7%) from non-remanent (non-switchable) components of polarization further confirming the good ferroelectric quality of the Sb-PMN-PT crystals. Also, the resistive-leakage characteristic of the doped crystal was analyzed using Time-dependent compensated hysteresis task. These results demonstrate that the Sb-doped PMN-PT crystal possesses excellent properties to achieve a variety of applications.

Magnetoelectric studies on CoFe2O4/0.5(BaTi0.8Zr0.2O3)-0.5(Ba0.7Ca0.3TiO3) lead-free bilayer thin films derived by the chemical solution deposition

Lead-free multiferroic bilayer thin films were fabricated on (111)Pt/Si substrate via a simple sol-gel chemical solution deposition, by altering the position of piezoelectric (Ba0.85Ca0.15) (Ti0.9Zr0.1)O3 (BCTZO) and ferromagnetic CoFe2O4 (CFO). Single layer BCTZO experiences the out-of-plane compressive stress, while this layer is under tensile strain in both the bilayers. The microstructural study confirms the formation of bilayers with expected chemical composition composed of multiple well-developed crystallites having no crystallographic dependencies. Thin films of BCTZO and CFO/BCTZO exhibited saturated ferroelectric hysteresis loops at room temperature with a Pr of 7.2 and 5.6 μC/cm2. The magnetic field induced shift in phonon vibrations coupled with direct magnetoelectric (ME) measurements demonstrated a stress-mediated coupling mechanism in the bilayers. We found a superior ME coefficient (105 MV/cm Oe) and dielectric tunability (∼52%) for CFO/BCTZO bilayer compared to the BCTZO/CFO bilayer, which demonstrates that the modification of strain state in bilayers is useful for the desired ME coupling. The BCTZO having piezoelectricity on par with that of lead-based ones can be useful to tailor lead-free ME applications.

Modification of ferroelectric and resistive properties of (Bi0.5Na0.5)(Nb0.5Fe0.5)O3 –PVDF composite

Pure (Bi0.5Na0.5)(Fe0.5Nb0.5)O3 [BNFN] ceramic was synthesized via a solid-state reaction route. PVDF and BNFN reinforced PVDF composite were prepared through a solution casting technique. The structure and surface morphology of the samples were studied using X-ray diffraction and scanning electron microscope respectively. Dielectric and impedance measurements were carried out in a frequency range of 1 kHz-1 MHz at different temperatures (25–130 °C). On addition of BNFN ceramic, a substantial increase in dielectric constant of the PVDF matrix was observed. The temperature has little effect on the dielectric constant of the composite in the said temperature range but its dielectric loss increases rapidly with rise in temperature. At room temperature the composite sample has dielectric constant of 161.7 and loss of 0.09. The composite exhibited a saturated ferroelectric hysteresis loop with remnant polarization value of 1.5μC/cm2. The electric response was investigated by impedance spectroscopy technique in terms of equivalent electric circuit. The ac conductivity as a function of frequency obeys Jonscher’s power law except a small deviation in the low-frequency region. The composite showed improved conductivity.

Multiferroic properties of a BiCrO3/BiFeO3 double-layered thin film prepared by chemical solution deposition

This study involved an investigation of the structural, electrical, and multiferroic properties of a BiCrO3/BiFeO3 (BCO/BFO) double-layered thin film that was prepared on a Pt(111)/Ti/SiO2/Si(100) substrate by using a chemical solution deposition method. X-ray diffraction and Raman spectroscopy studies revealed the formation of tetragonal and rhombohedral structures for the BCO/BFO double-layered thin film without any detectable secondary phases. A saturated ferroelectric hysteresis loop with a remnant polarization (2Pr) of 37μC/cm2 and a coercive field (2Ec) of 1004kV/cm at an applied electric field of 1154kV/cm and a ferromagnetic hysteresis loop with a 2Mr value of 0.044emu/cm2 and a 2Hc value of 276Oe at a magnetic field of 10kOe were observed for the BCO/BFO double-layered thin film at room temperature. The leakage current density of the BCO/BFO double-layered thin film was 2.88×10−4A/cm2 at an external electric field of 100kV/cm. The enhanced multiferroic properties observed for the BiCrO3/BiFeO3 thin film correlated with its net effects, such as a decrease in the oxygen vacancy density, a stabilization of the perovskite structure, and small changes in the lattice parameter caused by compressive strain resulting from the coupling of the BiFeO3 and BiCrO3 layers.

Preparation and Properties of Nanocrystalline Potassium Sodium Niobate Ceramics

Using average 30 nm grain sized potassium sodium niobate powders obtained by a novel Sol-Gel method as starting materials, nanocrystalline potassium sodium niobate ceramics with pure orthorhombic phase, relative density of above 99% and grain size of 40 nm were prepared by spark plasma sintering method under sintering temperature of 900 °C, sintering pressure of 30 MPa and sintering time of 1 min. The phase structure, micro-morphology, dielectric properties and ferroelectric properties of the ceramics were investigated. The results show that, differently from common micro-grain ceramics, dielectric constant of nanocrystalline potassium sodium niobate ceramics decreases to 341, which changes little with the temperature, and the ceramics have obvious dielectric relaxation (dispersion factor γ is 1.60), and a well saturated ferroelectric hysteresis loop with coercive field of 13.5 kV/cm and remanent polarization of 1.5 μC/cm. The abnormal properties can be attributed to the significant increasing content of grain boundary in nanocrystalline potassium sodium niobate ceramics, and it can be expected that if potassium sodium niobate ceramic has the critical size at room temperature, it would be less than 40 nm.

Electrical and Magnetic Properties of Multiferroic BiFeO<sub>3</sub> Ceramics Prepared Using Sol-Gel Derived Fine Powders

Insulating BiFeO3ceramics with a small amount of secondary phase Bi2Fe4O9were prepared by rapid sintering at 840 °C using sol-gel derived fine powders. The ceramics are dense and consist of grains of 3∼8μm in size. Their leakage current density remains lower than 5.5×10−5A/cm2under the applied electrical field below 100 kV/cm. The main conduction mechanism from 50−190 kV/cm is space-charge-limited-current relating to oxygen vacancies. The ceramics exhibit a saturated ferroelectric hysteresis loop with a remanent polarization (2Pr= 22μC/cm2) under the applied field of 165 kV/cm. Weak ferromagnetism was observed with a remanent magnetization 2Mrof 1.2×10−4μB/Fe at 300 K and of 1.8×10−4μB/Fe at 10 K.

Anion Driven [CuIIL2]n Frameworks: Crystal Structures, Guest-Encapsulation, Dielectric, and Possible Ferroelectric Properties

Employing a flexible phosphoramide ligand L, PhPO(NH3Py)2 (3Py = 3-pyridyl), four new Cu(II) cationic coordination assemblies 1, 1a, 2, and 3 of composition {[Cu2L4(H2O)2]·(ClO4)4·(H2O)5·(CH3OH)}∞, {[Cu3L6(H2O)3]·(ClO4)5·(NO3)·(H2O)11}∞, {[Cu4L8(H2O)5]·(NO3)8·L·(H2O)9}, and {[Cu3L6]·(NO3)6·(H2O)8·(CH3OH)2}, respectively, were synthesized. The compounds 1 and 1a having perchlorate and mixed perchlorate-nitrate anions, respectively, were obtained as noncentrosymmetric 1D-helical assemblies. However, 2 and 3 were obtained as discrete centrosymmetric assemblies of composition M4L8 and M3L6, respectively. Interestingly, 2 can encapsulate the hydrated potassium cation [K(H2O)8]+ in its intrinsic cavity. The ferroelectric measurements of 1 and 1a gave a well saturated ferroelectric hysteresis loop giving saturation polarization (Ps) values of 1.8 and 0.55 μC/cm2, respectively. This indicates that the presence of nitrate anion in the packing structure has an effect in altering the asymmetry of the system, which c...

Structure, conduction mechanisms and multiferroic properties of (Sm, Cr) co-doped Bi0.89Sm0.11Fe0.97Cr0.03O3–NiFe2O4 composition thin films

(Sm, Cr) co-doped Bi0.89Sm0.11Fe0.97 Cr0.03O3 (BSFC)–NiFe2O4 (NFO) composition thin films were successfully prepared on FTO/glass (SnO2:F) substrates via a sol–gel method. The structure, surface morphology, leakage current, ferroelectricity and ferromagnetism of BSFC–NFO composition thin film have been investigated. X-ray diffraction analysis indicates that the thin film is polycrystalline and consisted of a rhombohedral perovskite (R3m space group) BiFeO3 phase and a cubic (Fd-3m space group) inverse spinel NiFe2O4 phase. The BSFC–NFO composition thin film is promising in practical application because of its well saturated ferromagnetic (Ms = 19.45 emu/cm3) and ferroelectric (Pr = 39 µC/cm2) hysteresis loops with low order of leakage current density (J = 6.73 × 10−6 A/cm2, at an applied electric field of 100 kV/cm). Which suggest the ferroelectric and ferromagnetic properties can be improved by this composition thin film structure. Moreover, the various conduction mechanisms of BSFC–NFO composition thin film have also been studied.

Improved ferroelectricity of (1−x)Na0.5Bi0.5TiO3–xBaTiO3 ceramics rapidly sintered at low temperature

High insulating (1−x)Na0.5Bi0.5TiO3–xBaTiO3 (x=0–0.08) ceramics were rapidly sintered at low temperature and then enhanced polarizations were observed. (1−x)Na0.5Bi0.5TiO3–xBaTiO3 nano-powders were prepared by the sol–gel method and then their ceramics were rapidly sintered at 920–1150°C. According to the saturated ferroelectric hysteresis loops, the acquired saturated and remnant polarizations are ~48μC/cm2 and ~40μC/cm2 at x=0.03–0.08, and the coercive electric field decreases from ~70kV/cm of pure Na0.5Bi0.5TiO3 to ~30kV/cm at x=0.06–0.08. Furthermore, the piezoelectric d33 is 166.8pC/N at x=0.06, where the morphotropic phase boundaries occur. These improved properties are achieved because the leakage current is reduced through compressing the loss of Na and Bi components during ceramics׳ preparation process.

Room temperature multiferroic properties of (Bi0.95La0.05)(Fe0.97Mn0.03)O3/NiFe2O4 double layered thin film

(Bi0.95La0.05)(Fe0.97Mn0.03)O3/NiFe2O4 double layered thin film was prepared on a Pt(111)/Ti/SiO2/Si(100) substrate by a chemical solution deposition method. X-ray diffraction and Raman scattering spectroscopy studies confirmed the formation of the distorted rhombohedral perovskite and the inverse spinel cubic structures for the (Bi0.95La0.05)(Fe0.97Mn0.03)O3/NiFe2O4 double layered thin film. The (Bi0.95La0.05)(Fe0.97Mn0.03)O3/NiFe2O4 double layered thin film exhibited well saturated ferromagnetic (2Mr of 18.1emu/cm3 and 2Hc of 0.32kOe at 20kOe) and ferroelectric (2Pr of 60μC/cm2 and 2Ec of 813kV/cm at 866kV/cm) hysteresis loops with low order of leakage current density (4.5×10−6A/cm2 at an applied electric field of 100kV/cm), which suggest the ferroelectric and ferromagnetic multi-layers applications in real devices.

Studies on electrical and multiferroic properties of chemical solution deposited (Bi0.95La0.05)(Fe0.97Cr0.03)O3/CoFe2O4 double layered thin film capacitors

(Bi0.95La0.05)(Fe0.97Cr0.03)O3/CoFe2O4 double layered thin film was prepared on a Pt(111)/Ti/SiO2/Si(100) substrate by using a chemical solution deposition method. By introducing CoFe2O4 buffer layer, the leakage current density and the multiferroic properties have been significantly improved. Low leakage current density of 3.3×10−7A/cm2 at 100kV/cm, saturated ferroelectric hysteresis loop with 2Pr of 33μC/cm2 and 2Ec of 1120kV/cm at applied electric field of 1180kV/cm and ferromagnetic hysteresis loop with 2Mr of 39kA/m and 2Hc of 298kA/m at the magnetic field of 1587kA/m were observed in the double layered thin film at room temperature. The improved electrical and multiferroic properties are ascribed to the stabilized perovskite structure by reducing oxygen vacancies due to the co-doping elements, which may also suppress the cycloid spin structure in BiFeO3. Furthermore, CoFe2O4 buffer layer acts as a current barrier of (La, Cr) co-doped BiFeO3.

Effect of Li- and Ta-doping on the ferroelectric properties of Na0.5K0.5NbO3 thin films prepared by a chelate route

The effects of lithium and tantalum doping on the properties of Na0.5K0.5NbO3 (NKN) thin films were investigated. The films were fabricated by an optimized chelate route which offers the advantage of a simple and rapid solution synthesis. The optimization was achieved by investigating the effects of alkaline volatilization loss on film properties. In this way, undoped NKN thin films fabricated by this conventional method exhibited good ferroelectric properties (Pr ~ 8 μC/cm2, and Ec ~ 55 kV/cm for films annealed at 650 °C). The developed chelate route was then used to grow Li (5 %) and Ta (10 %) substituted thin films. Such structures allowed us to compare the effect of these dopant cations on phase formation, microstructure and ferroelectric properties. We show that both modifications produced a remarkable improvement on the ferroelectricity of the films. While the undoped material exhibited large leakage components in films annealed at 600 °C, films modified with Li or Ta presented well saturated ferroelectric hysteresis loops, indicating that those ions have a significant influence on the conducting process. The remnant polarizations of the Ta-doped films are greater than those of the Li-doped samples. This feature is however reversed for films annealed at low temperature (600 °C) due to the presence of a non-ferroelectric secondary phase in the Ta-doped composition.

Effects of oxygen ambient on dielectric and ferroelectric properties of lead free Lix(K0.5Na0.5)(1−x)NbO3 thin films derived from chemical solution deposition

We have fabricated lead free Lix(K0.5Na0.5)(1−x)NbO3 (LKNN) thin films by polyvinylpyrrolidone modified chemical solution deposition, and studied the effects of oxygen ambient on dielectric and ferroelectric properties. The obtained LKNN thin films exhibit significantly improved dielectric properties and saturated ferroelectric hysteresis loop. For LKNN (x=0.06) thin film, it showed dielectric constant of 471 and dielectric loss of tanδ<0.05 at 1kHz, and a remnant polarization 2Pr=14μC/cm2 and a coercive field Ec=90kV/cm, respectively. It was shown that the mutual effects of both oxygen ambient and small Li doping play a key role to suppress the volatilization of K and Na ions during thermal processing, which lead to smaller leakage current and thus excellent dielectric and ferroelectric properties.

Electrical properties of BiFeO3–BaTiO3 ceramics fabricated by mechanochemical synthesis and spark plasma sintering

0.75BiFeO3–0.25BaTiO3 (75BF–25BT) multiferroic powders were prepared by a mechanochemical synthesis at room temperature and the dense ceramics were sintered by a spark plasma sintering (SPS) at 1023–1073K. Microstructures of the ball milled powders and SPS ceramics were thoroughly investigated through X-ray diffraction and scanning electron microscopy, respectively. A bulk density up to 96% of theoretical density was achieved in the SPS ceramics. Dielectric spectra of the 75BF–25BT ceramics were characterized in a broad range of temperature and frequency. Typical saturated ferroelectric hysteresis loops with remnant polarization of 10μC/cm2 were obtained at room temperature, which makes it a good candidate for potential applications.

Observation of room temperature saturated ferroelectric polarization in Dy substituted BiFeO3 ceramics

High quality Bi1−xDyxFeO3 (0 ≤ x ≤ 0.15) ceramics have been fabricated by sintering Dy-doped BiFeO3 (BFO) precursor powders at a low temperature of 780 °C. The magnetic properties of BFO were improved by the introduction of Dy on the Bi-site. More importantly, well saturated ferroelectric hysteresis loops and polarization switching currents have been observed at room temperature. A large remnant polarization (2Pr) value of 62 μC/cm2 is achieved, which is the highest value reported so far for rare-earth-doped BFO ceramics. Moreover, mechanisms for improved multiferroic properties depending on chemical doping-caused structure evolutions have also been discussed.