Effects of dwell time during sintering on electrical properties of 0.98(K_(0.5)Na_(0.5))NbO_3-0.02LaFeO_3 ceramics

The effects of dwell time on the phase structure, microstructure, and electrical properties were investigated for the 0.98（K0.sNa0.5）NbO3-0.02LaFeO3 ceramics （abbreviated as 0.98KNN-0.02LF）. All the ceramics sintered for different dwell time are of pure phase and the peak intensity of the 0.98KNN-0.02LF ceramics becomes stronger with a longer dwell time. Denser microstructures with larger grain size are developed for the sample with a longer dwell time. The maximum dielectric permittivity decreases with increasing the dwell time, and the deteriorative dielectric properties are due to the increasing grain size and the domain wall motion. Ferroelectric properties results indicate that 2Pr value slightly decreases with increasing the dwell time, while the 2Ec value increases. Consequently, the 0.98KNN-0.02LF ceramic sintered at 1150 ℃ for 2 h shows optimum dielectric properties （er=2253 and tan fi〈5%） and ferroelectric properties （2Pr=34.51 gC/cm2 and 2Ec=5.07 kV/mm）.

Structural and electrical properties of Nd ion modified lead zirconate titanate nanopowders and ceramics

A modified sol-gel method is used for synthesizing Nd ion doped lead zirconate titanate nanopowders Pb1-3x/2^NdxZr0.52Ti0.48O3 （PNZT） in an ethylene glycol system with zirconium nitrate as zirconium source. The results show that it is critical to add lead acetate after the reaction of zirconium nitrate with tetrabutyl titanate in the ethylene glycol system for preparing PNZT with an exact fraction of titanium content. It has been observed that the dopant of excess Nd ions can effectively improve the sintered densification and activity of the PNZT ceramics. Piezoelectric, dielectric and ferroelectric properties of the PNZT ceramics are remarkably enhanced as compared with those of monolithic lead zirconate titanate （PZT）. Especially, the supreme values of piezoelectric constant （d33） and dielectric constant （ε） for the PNZT are both about two times that of the monolithic PZT and moreover, the remnant polarization （Pr） also increases by 30%. According to the analysis of the structures and properties, we attribute the improvement in electrical properties to the lead vacancies caused by the doping of Nd ions.

Ferroelectric properties of sol-gel derived Nd-doped SrBi_4Ti_4O_(15) thin films

Neodymium-doped strontium bismuth titanate （SrBi4-xNdxTi4O15） ferroelectric thin films were fabricated using the sol-gel method on Pt/Ti/SiO2/Si substrates. The influence of Nd content on the microstructure and ferroelectric properties of SrBi4-xNdxTi4O15 thin films were systematically studied. The results indicated that the SrBi3.88Nd0.12Ti4O15 （SBNT0.12） thin films had better ferroelectric properties, with a remanent polarization of （2Pr） of 34.3 μC/cm^2 and a coercive field （2Ec） of 220 kV/cm. This could be attributed to the fact that SBNT0.12 ferroelectric thin films consisted of more and larger ball-like grains, approximately 150-200 nm, with structure distortion, which greatly contributed to the improvement of the ferroelectric properties of the films. Furthermore, the film exhibited a good fatigue resistant property. The value of 2Pr after 10^10 switching cycles did not change significantly. The SrBi3.88Nd0.12Ti4O15 films were promising candidates for the application of FeRAMs.

Influences of Ho Doping on Structure,Ferroelectric,Energy Storage and Optical Properties of KNN-SYbN Transparent Ceramics

Ho doping 0.825K_(0.5)Na_(0.5)NbO_(3)-0.175Sr(Yb_(0.5)Nb_(0.5))_(O3)(KNN-SYbN-x%Ho)transparent ceramics were prepared by solid-state sintering method.The structure,ferroelectric,energy storage,and optical properties of KNN-SYbN-x%Ho were explored.With the addition of Ho,under the excitation of a 980 nm laser,the ceramics exhibit up-conversion luminescence properties with wavelengths of 550 nm and 670 nm,however,the ceramics change from pseudo-cubic phase to triphase-orthorhombic phase and the light transmittance decreases.The addition of Ho significantly enhances the ferroelectric properties and the energy storage performance of KNN-SYbN-x%Ho ceramics.When x=0.15,the residual polarization P_(r)=9.11μC/cm^(2),while x=0.20,the maximum energy storage density W_(rec) reaches 0.26 J/cm^(3),and the energy storage efficiencyηreaches 87.1%.

Effect of Pb Substitution on the Microstructure and Ferroelectric Properties of Ba_(0.7)Sr_(0.3)TiO_3 Ceramic

Ferroelectric Ba0.7Sr0.3TiO3（BST） and partially Pb^2＋ substituted for Ba^2＋ ceramics （Ba0.7-xPbx）Sr0.3TiO3 （x=0.1-0.4, BPST） were prepared by using conventional solid-reaction method. XRD analysis shows that the samples microstructure changes from cubic phase to tetragonal one with the Pb^2＋ content increasing. ESEM analysis shows that the Pb^2＋ substituted samples have a denser and more uniform surface morphology than that of pure BST. Measured electrical properties suggest that the Pb^2＋ substitution for Ba^2＋ in the BST system enhances the ferroelectric performance obviously when x=0.2. In addition, the substitution increases the samples Curie temperature （To） r （Ba0.5Pb0.2）Sr0.3TiO3 ceramic has good ferroelectric properties measured at a maximal electric field of 30 kV/cm under the condition of room temperature. The corresponding saturated polarization （Ps）, remnant polarization （Pr） and coercive field （Ec） is respectively 15.687 μC/cm^2, 8.100 μ C/cm^2 and 6.611 kV/cm. The measured Tc of （Ba0.5Pb0.2）Sr0.3TiO3 is 117 ℃.

Multiferroic properties and exchange bias in Bi_(1-x)Sr_xFeO_3(x=0–0.6) ceramics

Multiferroic properties and exchange bias （EB） in Bi1-xSrxFeO3 （x = 0-0.6） ceramics synthesized by a modified Pechini method are investigated. Sr concentration dependence of structure distorting, ferroelectric properties, and dielectric properties were studied at room temperature. Appropriate Sr doping （x = 0.05-0.2） has been found to decrease the conductivity, enhance ferroelectric properties and give rise to high dielectric constant. Compared with antiferromagnetic BiFeO3 compound, BSFO-x （O≤x ≤0.4） ceramics show weak ferromagnetism at room temperature, and their exchange bias field and vertical magnetization shift are observed and exhibit a strong dependence on the content of Sr. This observed EB effect which keeps stable in BSFO ceramics at 10 K tend to vanish at room temperature with Sr concentration over 0.4.

Crystallization and Electrical Properties of (Ba_(0.4)Pb_(0.3))Sr_(0.3)TiO_3 Thin Film by Pulsed Laser Deposition

（Ba0.4Pb0.3）Sr0.3TiO3 thin films were fabricated via pulsed laser deposition （PLD） technique on Pt/TiO2/SiO2/Si substrate. The crystallization of the films was characterized by XRD and FSEM, and the experimental results suggested deposition parameters, especially the deposition temperature was the key factor in forming the perovskite structure. The dielectric properties of the film deposited with optimized parameters were studied by an Agilent 4294A impedance analyzer at 1 MHz. The dielectric constant was 772, and the loss tangent was 0.006. In addition, the well-shaped hysteresis loop also showed that the film had a well performance in ferroelectric. The saturated polarization P, remnant polarization Pr and coercive field E were about 4.6 μC/cm2, 2.5 μC/cm2 and 23 kV/cm （the coercive voltage is 0.7 V）, respectively. It is suggested the film should be a promising candidate for microwave applications and nonvolatile ferroelectric random access memories （NvFeRAMs）.

Effect of annealing process on structures and ferroelectric properties of Ca_(0.4)Sr_(0.6)Bi_(3.95)Nd_(0.05)Ti_4O_(15) thin films

Ca0.4Sr0.6Bi3.95Nd0.05Ti4O15 （C0.4S0.6BNT） ferroelectric thin films were prepared on Pt/Ti/SiO2/Si substrates by sol-gel method. Effect of annealing process （time and temperature） on structures and ferroelectric properties of C0.4S0.6BNT thin film was investigated. The relative intensity of （200） peak increased first then decreased with annealing temperature and became predominant at 800 ℃. In contrast, no evident change could be observed in the （001） peak. The remnant polarization （Pr） and coercive field （Ec） for C0.4S0.6BNT film annealed at 800℃ for 5 min were 21.6μC/cm2 and 68.3 kV/cm, respectively.

Potts-Ising model for simulation of polarization switching in polycrystalline ferroelectrics

This paper proposes a scheme based on the Potts and Ising models for simulating polarization switching of polycrystalline ferroelectrics using the Monte Carlo method. The polycrystalline texture with different average grain size is produced from the Potts model. Then Ising model is implemented in the polycrystalline texture to produce the domain pattern and hysteresis loop. The domain patterns and hysteresis loops have been obtained for polycrystalline texture with different average grain size. From the results of domain pattern evolution process under an applied electric field using this scheme, an extended domain, which covers more than one grain with polarization aligned roughly in the same direction, has been observed during the polarization reversal. This scheme can well reproduce the basic properties of polycrystalline ferroelectrics and is a valuable tool for exploring the physical properties of polycrystalline ferroelectrics.

Structure and Properties of Mg-doped SrBi_4Ti_4O_(15) Bi-layered Compounds

The structure and properties of Mg-doped SrBi4Ti4O15（SBT） were dicussed. Mg substitution into SBT had two possibilities states with the dopant amount variety. Mg cation substituted mostly into Sr^2＋ and the amount proportion was 68.11%.Mg ion will substitute into Ti ion site in perovskite layer when the doping amount increases. Polarization increases sharply when x=0.1 and then decreases becauses of the domain pinning. The Curie temperature of Mg-doped SBT is about 300 ℃ and there is a broad diffuse phase transition near Tc with a flat peak near the Ta of SBT.

Effect of La Doping on Microstructure and Ferroelectric Prop-erties of Bi_4Ti_3O_(12) Thin Films Prepared by Sol-gel Method

The Bi4Ti3Oi2 and Bi3.25La0.75Ti3O12 thin films were prepared on the Pt/Ti/SiO2/Si substrate using the sol-gel method. The effect of La doping on the microstructure and ferroelectric properties of Bi4Ti3O12 films were investigated. Both the Bi4Ti3O12 and Bi3.25La0.75Ti3O12 thin films exhibited typical bismuth layered perovskite structure. The 2Pr （remanent polarization） value of Bi3.25La0.75Ti3O12 thin films is 18.6 μC/cm^2, which is much larger than that of Bi4Ti3O12 thin films. And the Bi3.2eLa0.75Ti3O12 films show fatigue-free behavior, while the Bi4Ti3O12 thin films exhibit the fatigue problem. The mechanism of improvement of La doping was discussed.

Characterization of PZT/PVC Composites Added with Carbon Black

A new three-phase PZT C/PVC composite comprising PZT（50 vol%）,nanocrystalline PVC （50 vol%） and a small volume fraction f of black（C0was prepared by the hot-pressing technique.The dielectric property of the composite as α function of the frequency and the dielectric and piezoelectric properties as α function of the volume fraction f of C were studied.The measured dielectric property demonstrates that α percolation transition occurs in the three-phase composites as in normal two-phase metal-insulator continuum media.The dielectric constant varies slightly with f at f〈0.1 and increases rapidly when f is close to the percolation threshold at 1kHz.The optimum properties were obtained for f=0.5 before the percolation threshold in the PZT/C/PVC（50/f/（50-f）vol%）composite with its d33（20pC/N） being 50% higher than that of the PZT/PVC（50/50vol%）,and its g33（47.23×10^-3Vm/N）and Kp（0.25） much higher than the earlier reported values,XRD patterns and P-E hysteresis loops were used to interpret the experimental results.

Enhanced ferroelectricity and ferromagnetism in Bi_(0.9)Ba_(0.1)FeO_3/La_(2/3)Sr_(1/3)MnO_3 heterostructure grown by pulsed laser deposition

Bi0.9Ba0.lFeO3 （BBFO）/La2/3Srl/3MnO3 （LSMO） heterostructures are fabricated on LaA103 （100） substrates by pulsed laser deposition. Giant remnant polarization value （~ 85 μC/cm2） and large saturated magnetization value （~ 12.4 emu/cm3） for BBFO/LSMO heterostructures are demonstrated at room temperature. Mixed ferroelectric domain structures and low leakage current are observed and in favor of enhanced ferroelectrie properties in the BBFO/LSMO het- erostructures. The magnetic field-dependent magnetization measurements reveal the enhancement in the magnetic moment and improved magnetic hysteresis loop originating from the BBFO/LSMO interface. The heterostructure is proved to be effective in enhancing the ferroelectric and ferromagnetic performances in multiferroic BFO films at room temperature.

Effect of grain size on ferroelectric and dielectric properties of Bi_(3.25)La_(0.75)Ti_(3)O_(12) thin films prepared by rf-magnetron sputtering

Bi_(3.25)La_(0.75)Ti_(3)O_(12)(BLT)thin films are promising materials used in non-volatile memories.In this work,BLT films were deposited on Pt(111)/Ti/SiO_(2)/Si substrates by rf-magnetron sputtering method followed by annealing treatments.The microstructures of BLT thin films were investigated via X-ray diffraction(XRD),scanning electron microscopy(SEM)and atomic force microscopy(AFM).With the increase in annealing temperature,the grain size increased significantly and the preferred crystalline orientation changed.A well-saturated hysteresis loop with a superior remnant polarization of 15.4μC/cm^(2) was obtained for BLT thin films annealed at 700°C.The results show that the dielectric constant decreased with the increase in grain sizes.

The role ofγ-C2H5NO2 as a new transient liquid phase in cold sintering process of BaTiO3 composites

Dielectric materials,such as barium titanate(BT)-based materials,have excellent dielectric properties but require high temperatures(above 1300℃)for ceramic fabrication,leading to high costs and energy loss.The cold sintering process(CSP)offers a solution to these issues and is gaining worldwide attention as an innovative fabrication route.In this work,we proposed an alternative organic ferroelectric phase,gamma-glycine(γ-GC),which acts as a transient liquid phase to fabricate high-density composites with barium titanate(BT)at low temperatures through CSP.Our findings show that the density of 15γ-GC/85BT reached 96.7%±1.6%when it was sintered at 120℃for 6 h under 10 MPa uniaxial pressure.Scanning electron microscopy‒energy dispersive X-ray spectroscopy(SEM‒EDS)mappings of the composite suggested thatγ-GC completely underwent the precipitation-dissolution process and,therefore,filled between BT particles.Moreover,X-ray diffraction(XRD)and Fourier-transform infrared spectroscopy(FTIR)confirmed the preservation ofγ-GC without undesired phase transformation.In addition,the ferroelectric and dielectric properties ofγ-GC/BT composites have been reported.The high dielectric constant(εr)was 3600,and the low dielectric loss(tanδ)was 1.20 at 200℃and 100 kHz for the 15γ-GC/85BT composite.The hysteresis loop showed a remanent polarization(Pr)of 0.55µC·cm^(−2)and a coercive field(Ec)of 7.25 kV·cm^(−1).Our findings reaffirmed that an organic ferroelectric material(γ-GC)can act as a transient liquid phase in a CSP that can successfully and sustainably fabricateγ-GC/BT composites at low temperatures while delivering outstandingly high performance.

A novel lead-free Na_(0.5)Bi_(0.5)TiO_(3)-based ceramic with superior comprehensive energy storage and discharge properties for dielectric capacitor applications

Na_(0.5)Bi_(0.5)TiO_(3)(NBT)-based ceramics have been widely used as dielectric materials for energy storage capacitors because of their environmental friendliness and excellent ferroelectric properties.However,their energy storage performance still needs to be further improved to satisfy the increasing demand.Herein,we report a novel 0.90(Na_(0.5)Bi_(0.5))0.7Sr_(0.3)TiO_(3-0.10)Bi(Ni_(0.5)Sn_(0.5))O_(3)(0.90NBST-0.10BNS)ceramic with significantly improved energy density(5.0 J cm3),enhanced recoverable energy density(4.18 J cm^(3))and high energy efficiency(83.64%)through the incorporation of Bi(Ni0.5Sn0.5)O3(BNS),due to the increased breakdown strength and the relaxation ferroelectric(RFE)properties.The first-order reversal curve(FORC)measurements confirm that the addition of BNS improves RFE properties by breaking the order of long-range ferroelectricity.The 0.90NBST-0.10BNS ceramic also possesses an outstanding temperature and frequency stability of energy storage properties in the range of 20C e140C and 1 Hze100 Hz,respectively.More importantly,the discharge properties characterized by a preeminent power density(36.19 MW cm^(3)),transient energy release times(144.2 ns),and high discharge energy density(1.16 J cm3)also synchronously observed in 0.90NBST-0.10BNS ceramic.These results show that the 0.90NBST-0.10BNS ceramic with outstanding comprehensive performances is a promising energy storage ceramic candidate for capacitors in high power systems.

Effect of Nd2O3 doping on the electrical properties of Ba0.96Ca0.04Ti0.90Sn0.10O3 ceramics

The Ba（0.96）Ca（0.04）Ti（0.90）Sn（0.10）O3-xNd2 O3（x = 0-0.08%） ceramics were prepared via traditional solid-state sintering method. The influences of Nd3＋ substitution on the phase structure, dielectric properties,piezoelectric and ferroelectric properties of the ceramics were investigated. All the samples possess pure BaTiO3-type perovskite structure. MPB with orthorhombic and tetragonal phase coexist at around x = 0.03-0.04. Nd^（3＋） doping decreases both Tc and T（O-T） to lower temperature. All the samples exhibit an intermediate state with the coexistence of ferroelectric and diffuse relaxor ferroelectric behavior with the addition of Nd^（3＋）. The electric properties of the ceramics were optimized at x = 0.03 with d33, Kp, εr and Pr values of 545 pC/N, 51.9%, 24,412 and 10.74 μC/cm^2.

Effect of rare earth on physical properties of Na_(0.5)Bi_(0.5)TiO_(3)system:A density functional theory investigation

Na_(0.5)(Bi_(3/4)RE_(1/4))_(0.5)TiO_(3)(RENBT,RE=Nd,Gd,Dy,and Ho)compounds were investigated in the framework of first-principles calculations using the full potential linearized augmented plane wave(FP-LAPW)method based on the spin-polarized density functional theory implemented in the WIEN2k code.Combined charge density distribution and Ti K-edge X-ray absorption spectra reveal that the RENBT compositions with high polarization values are accompanied by a higher TiO_(6)distortion,DyNBT,and NdNBT compounds.The effect of the rare-earth elements on the polarization is confirmed experimentally with the collection of the hysteresis loops.The investigation of the electronic properties of the compounds highlights the emergence of a magnetization owing to the 4f orbital effect of the rare-earth elements.Besides,the investigation of the chemical ordering shows a short-range chemical ordering for the pure composition and an increased A-site disorder for dysprosium doped NBT system.The increased disorder may speak for increased relaxor properties in the RE doped compositions.

Effect of Tb Doping on Structural and Electrical Properties of BiFeO_3 Thin Films Prepared by Sol-Gel Technique

Bil_xTbxFe03 thin films were prepared on Sn02 （fluorine doped tin oxide） substrates by a sol-gel method. The structural and electrical properties of the BiFe03 thin films were characterized and tested. The results indicated that the diffraction peak of the Tb-doped BiFe03 films was shifted towards right as the doping amounts were increased. The structure was transformed from the rhombohedral to tetragonal/orthorhombic phase. The Bio.sgTbo.11Fe03 thin film showed the well-developed P-E loops, which enhanced remnant polarization （Pr = 88.05 μC/cm2） at room temperature. The dielectric constant and dielectric loss of Bio.sgTbo.llFe03 thin film at 100 kHz were 185 and 0.018, respectively. Furthermore, the Bio.seTbo.llFe03 thin film showed a relatively low leakage current density of 2.07×10-5 A/cm2 at an applied electric field of 150 kV/cm. The X- ray photoelectron spectroscopy （XPS） spectra indicated that the presence of Fe2＋ ions in the Bio.egTbo.11Fe03 thin film was less than that in the pure BiFe03.

Enhanced electrical properties in bilayered ferroelectric thin films

Sr2Bi4Ti5O18(SBTi) single layered and Sr2Bi4Ti5O18 /Pb(Zr0.53Ti0.47)O3(SBTi/PZT) bilayered thin films have been prepared on Pt/TiO2/SiO2/Si substrates by pulsed-laser deposition(PLD).The related structural characterizations and electrical properties have been comparatively investigated.X-ray diffraction reveals that both films have crystallized into perovskite phases and scanning electron microscopy shows the sharp interfaces.Both films show well-saturated ferroelectric hysteresis loops,however,compared with the single layered SBTi films,the SBTi/PZT bilayered films have significantly increased remnant polarization(Pr) and decreased coercive field(Ec),with the applied field of 260 kV/cm.The measured Pr and Ec of SBTi and SBTi/PZT films were 7.9 C/cm 2,88.1 kV/cm and 13.0 C/cm 2,51.2 kV/cm,respectively.In addition,both films showed good fatigue-free characteristics,the switchable polarization decreased by 9% and 11% of the initial values after 2.2 10 9 switching cycles for the SBTi single layered films and the SBTi/PZT bilayered films,respectively.Our results may provide some guidelines for further optimization of multilayered ferroelectric thin films.