Dielectric,pyroelectric and ferroelectric behavior of PZTN 65/35/x ferroelectric ceramic system

Niobium doping lead zirconate titanate [PZTN 65/35/x (x = 1, 2, 4, 5)] ferroelectric ceramics show perovskite structure and a rombohedral phase. The average grain size, the maximum dielectric permittivity, the transition temperature and the remanent polarization decrease when the niobium concentration increases, while the coercive field does not show any particular behavior and the porosity increases. The results are discussed taking into account the incorporation of the niobium to the lattice and the variation of the grain size. Preliminary results of the pyroelectric behavior are shown.     

Influence of Cd doping on the electro-strain of barium zirconate titanate ceramics

Cadmium doped barium zirconate titanate (Ba_1−xCd_x)(Zr_0.13Ti_0.87)O₃ (BCDZT) ferroelectric ceramic compositions with x=0, 0.02, 0.04 and 0.06 have been prepared by solid state reaction method. X-ray diffraction studies reveal a pseudocubic structure. For increasing Cd content, the bulk ceramic micro-structure reveals an increasing grain size and density. Variations in the dielectric, piezoelectric and unipolar electric field induced strain characteristics are discussed. Increasing Cd content reduces the coercive field, increases the remnant polarization and does not affect the ferroelectric-paraelectric phase transition temperature (~60 °C). An optimum Cd content x=0.06 produces highly resistive ceramics with low dielectric loss (tanδ=0.019), and a maximum value of piezoelectric charge constant d₃₃=114 pC/N and unipolar electro-strain of ~0.07%.     

Templated grain growth of high coercive field CuO-doped textured PYN-PMN-PT ceramics

This paper explores the templated grain growth and texturing of Pb(Yb_1/2Nb_1/2)O₃-Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PYN-PMN-PT) ceramics. A PbO-CuO liquid phase was determined to substantially increase the growth of PYN-PMN-PT on barium titanate template particles. Texturing resulted in an 83% enhancement in strain behavior (754 pm/V) compared with random PYN-PMN-PT ceramics (413 pm/V). The increased Pb(Yb_1/2Nb_1/2)O₃ (PYN) content of textured 21PYN-41PMN-38PT resulted in a high coercive field of 13.9 kV/cm. Residual barium titanate templates reduced the polarization from 33.7 to 26.2 µC/cm² and slightly decreased the Curie temperature (236-224°C). These results show that textured PYN-PMN-PT is a promising material for high strain and coercive field transducers.     

Influence of cobalt and sintering temperature on structure and electrical properties of BaZr0.05Ti0.95O3 ceramics

Pure and Co-modified BaZr_0.05Ti_0.95O₃ ceramics were fabricated by the traditional solid state reaction technique. The influence of cobalt and sintering temperature on structure, dielectric, ferroelectric properties and diffuse phase transition of BZT ceramics were investigated systematically. 1300 °C was the optimal sintering temperature for BZT ceramics. The solid solubility limit of Co ions in BZT matrix was determined to be 0.4 mol%. The introduction of a moderate amount of Co ions was believed to benefit the microstructure development and make the grain size more uniform. Compared with undoped counterparts, 0.4 mol% Co-modified ceramics showed equivalent ferroelectric properties with a high remnant polarization (P_r=9.6 μC/cm²) and a low coercive field (E_c=0.21 kV/mm). Besides these, a relative high dielectric coefficient (ε_r=2030) and a low dielectric loss (tan δ=1.85%) were also obtained on this composition. The degree of diffuse phase transition was enhanced by the addition of Co ions. The related mechanism of the diffused phase transition behavior was discussed.     

Effect of Sm3+ doping on ferroelectric,energy storage and photoluminescence properties of BaTiO3 ceramics

Rare earth doped ferroelectric ceramics have attracted much attention due to their great potential application for novel multifunctional optical-electro devices. Herein, the x% mol Sm³⁺ doped BaTiO₃ (BTO:xSm³⁺) ceramics were fabricated by the conventional solid-state reaction method. The Sm³⁺ ions composition dependent phase structure, ferroelectric, energy storage and photoluminescence properties were systematically investigated. With the increase of Sm³⁺ ions composition, the remanent polarization decreases dramatically from 15.705 μC/cm² (BTO) to 7.132 μC/cm² (BTO:3.0%Sm³⁺), but the energy storage density and efficiency increase greatly with a relative change of 79.76% and 31.13%, respectively. Furthermore, Sm³⁺ doping causes the transformation from the tetragonal to pseudo-cubic phase for BTO ceramics at room temperature, resulting in a broader temperature transition range from the ferroelectric to paraelectric phase and a lower Curie temperature. Particularly, the pure BTO and BTO:xSm³⁺ ceramics show great thermal stability for energy storage properties. In addition, under the excitation of 408 nm near-ultraviolet light, the BTO:xSm³⁺ ceramics exhibit the strongest orange-red emission peak around 596 nm with a large relative tunability of intensity by 88.97%. The results suggest that the BTO:xSm³⁺ ceramics are suitable for the design of optoelectronic devices.     

Low temperature synthesis and dielectric, ferroelectric and piezoelectric study of microwave sintered BaTiO3 ceramics

Barium titanate (BaTiO₃/BT) ferroelectric system was synthesized in single perovskite phase at low temperature by using powders derived from modified solid state reaction (MSSR) and sintered by microwave (MW) processing routes. Conventional calcination temperature was optimized at 900 °C for 4 h. MW sintering of BT samples was carried out at 1100 °C for 30 min to get dense (98% density) ceramics. Room temperature (RT) dielectric constant (?_r) and dielectric loss (tan δ) at 1 kHz frequency of MW sintered BT samples was found to be ∼2500 and 0.03, respectively. Saturated polarization vs. electric field (P-E) loops with remnant polarization (P_r) ∼6 μC/cm² and coercive field (E_c) ∼1.45 kV/cm confirmed the ferroelectric nature of MW sintered BT samples. Piezoelectric coefficient from strain vs. electric field (S-E) loops study was found to be 335 pm/V.     

Effects of uniaxial prestress on the ferroelectric hysteretic response of soft PZT

This paper deals with the influence of preload stress on the ferroelectric hysteretic behavior of piezoelectric ceramics. The polarization and strain versus electric field hysteresis loops were measured for soft lead zirconate titanate (PZT) piezoceramic material under various uniaxial compressive stress preloads of up to −400 MPa. The investigation revealed that the superimposed compression load reduced the remnant polarization, decreased the coercive field, and also had a significant impact on the dielectric and piezoelectric properties. With increasing mechanical load, dielectric hysteresis and butterfly hysteresis became less and less pronounced, as the compressive stress prevented full alignment of the domains and induced mechanical depolarization. The slopes of the polarization and strain curves at zero electric field were measured to evaluate the dependence of permittivity and piezoelectric coefficients on the prestress. The experimental results were interpreted in terms of the non-180° domain switching process under combined electromechanical loading.     

Magneto-electric properties of xNi0.7Zn0.3Fe2O4 – (1-x)BaTiO3 multiferroic composites

Di-phase ceramic composites, with general formula xNi_0.7Zn_0.3Fe₂O₄ – (1-x)BaTiO₃(x = 0.9, 0.7, 0.5, 0.3, 0.1), were prepared by a mixing method. X-ray analysis, for powder and ceramics, indicated the formation of ferrite and barium titanate phases without the presence of the impurities. SEM analysis indicated that the composite morphology contained two types of grains, polygonal and rounded. Homogeneous microstructure and the smallest grain size were obtained in ceramics with 70% of barium titanate. The electrical properties of these materials were investigated using impedance spectroscopy, dielectric and ferroelectric measurements. The NZF-BT(30-70) composite has shown better electrical properties in comparison to other investigated ceramics, confirmed by dielectric and ferroelectric data analysis. Saturation magnetization and coercive field decreased with the increase of the content of ferroelectric phase.     

Influence of AlF3 Concentration on Microstructures and Energy Storage Properties of Barium Strontium Titanate Glass Ceramics

The effect of AlF₃ concentration on the microstructures and energy storage properties of barium strontium titanate glass ceramics was studied. Scanning electron microscopy investigations revealed that the addition of AlF₃ significantly changed the microstructure morphology of the glass ceramics. Dielectric measurements indicated that the dielectric constant has a maximum value at 2 mol% AlF₃ concentration. Using polarization‐electric field measurements, the energy storage properties were found to be influenced strongly by the AlF₃ concentration. The correlation between the microstructure and the dielectric property in the barium strontium titanate glass ceramics with different AlF₃ concentrations was qualitatively discussed.     

Barium Zirconate-Lead Titanate Ferroelectric Ceramics

Hot-pressed barium zirconate-lead titanate ceramics have been examined to determine crystal-line symmetry and dielectric, ferroelectric, and piezoelectric properties. Barium zirconate additions to lead titanate form solid solutions with a decreasing tetragonal c/a axial ratio until at 60PbTiO₃–40BaZrO₃ to 75PbTiO₃–25BaZrO₃ the ceramics have coercive forces low enough to permit polarization. High-coercive-force piezo-electric ceramics are formed with k_p up to 0.30 and d₃₃ up to 110 × 10⁻¹² coulombs per newton.     

Fatigue of Ferroelectric Polarization and the Electric Field Induced Strain in Lead Lanthanum Zirconate Titanate Ceramics

Fatigue of ferroelectric polarization and the electric field induced strain is investigated in lead lanthanum zirconate titanate ceramics. Fatigue rate increases as the coercive field or the hysteretic nature of the electric field induced polarization of the ferroelectric ceramics increases. The ferroelectric polarization lost during fatigue can be partly restored by decreasing the frequency and increasing the amplitude of the applied ac electric field. The ferroelectric fatigue is modeled phenomenologically by an increase of the energy barrier for the ferroelectric switching and atomistically by a coupling of the spontaneous polarization with defects and/or space charge in the orientation of ferroelectric fatigue.     

纳米钛酸钡的掺杂对陶瓷性能的影响

采用掺杂纳米级钛酸钡和碳酸锰的方法,观察了掺杂不同量纳米级钛酸钡和碳酸锰后的钛酸钡坯片烧结所得陶瓷表面的显微组织形貌的变化,研究了单一掺杂纳米级钛酸钡、单一掺杂碳酸锰、复合掺杂碳酸锰+纳米级钛酸钡对陶瓷制品晶粒尺寸与介电性能的影响。结果表明：掺杂纳米级钛酸钡对钛酸钡陶瓷制品的介电性能有显著的提升,但是随着掺杂量的进一步增加,其介电性能的变化不大;掺杂碳酸锰对钛酸钡陶瓷晶粒的细化效果优于掺杂纳米级钛酸钡的效果;复合掺杂1%（质量分数,下同）碳酸锰+1%纳米级钛酸钡所得陶瓷的致密性高于单一掺杂1%碳酸锰的效果。     

The dielectric properties of BaTiO3 based ceramics co-doped with Bi/Mn

BaTiO₃ based ceramics (with some additives such as ZrO₂, SnO₂, etc.) were prepared by solid state reaction. Mn²⁺ or Mn³⁺ as an acceptor substituting for Ti⁴⁺ in B site and Bi³⁺ as a donor substituting for Ba²⁺ in A site were co-doped in BaTiO₃ based ceramics. The dielectric properties of BaTiO₃ based ceramics co-doped with Bi/Mn were investigated. The results show that the dielectric properties of BaTiO₃ based ceramics co-doped with Bi/Mn are affected by the mole ratio of donor and acceptor (Bi/Mn). When the mole ratio of donor and acceptor is high, dielectric dispersion behavior was observed and the dielectric constant decrease and remnant polarization, coercive field and piezoelectric constant will varied. When Bi varied from 1.0% to 2.0 mol% (Mn = 0.8 mol%), remnant polarization from 10.35 to 2.25 μC/cm², coercive field from 4 to 2.75 kV/cm, and piezoelectric constant d₃₃ from 137 to 36 pC/N respectively.     

Abnormal frequency dependent polarization fatigue behavior in aged Pb(Mn1/3Sb2/3)O3-Pb(Zr,Ti)O3 ferroelectric ceramics

The fatigue behavior of 0.05Pb(Mn_1/3Sb_2/3)O₃–0.50PbZrO₃–0.45PbTiO₃ ceramics (abbreviated as PMS-PZT) is investigated. Special attention is paid to the effect of applied electric frequency on the evolution of polarization-electric field, strain-electric field hysteresis loops as well as the parameters of remnant polarization, internal bias field and coercive field extracted directly from the former hysteresis loops or calculated according to these loops. It is found that the fatigue behavior is different from that of donor doped Pb(Zr,Ti)O₃ (PZT) ceramics demonstrated by the tendency of increasing remnant polarization, the decreased internal bias field, decreased asymmetry of polarization-electric and strain-electric loops with increasing fatigue duration when PMS-PZT ceramics fatigued at lower frequency (i.e. 5 Hz or 500 Hz). The dynamic of oxygen vacancies under the application of bipolar electric field is supposed to be associated with the abnormal fatigue behavior. In addition, no matter at which cyclic frequency samples fatigued, coercive field shows the tendency of decrease with increasing fatigue duration except for sample fatigued at 5 kHz in which coercive field first decreases and then increases. According to phase structure and the empirical Rayleigh analysis, phase transition during fatigue treatment is supposed to be account for the decrease of coercive field.     

Electric fatigue of ceramic–polymer composite film under cyclic electric field

Electric fatigue under cyclic electric loading was characterized for 0–3 composite film with particles of barium titanate dispersed in poly(vinylidene fluoride‐trifluoroethylene) copolymer matrix. The data reveal that both remanant polarization and coercive field decrease as the cycle number increases. Scanning electron microscope observation and X‐ray diffraction analysis were carried out to examine the morphology and microstructure change during the electric field cycling. On cyclic electric field, large quantities of flaw‐like defects occur and the crystallites grow in size, leading to reduction of interfacial layers between the crystalline and amorphous regions. The relationship between the microstructure evolution and the polarization behavior is discussed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Long term stability of electrocaloric response in barium zirconate titanate

The stability of the electrocaloric effect under electric field cycling is an important consideration in the development of solid-state cooling devices. Here we report measurements carried out on Ba(Zr_0.2Ti_0.8)O₃ ceramics which reveal that the adiabatic temperature change, polarization-electric field hysteresis loops and dielectric permittivity/loss show stable behavior up to 10⁵ cycles. We further demonstrate that the loss in electrocaloric response observed after 10⁵ cycles is associated with the migration of oxygen vacancies. As a result, the electrical properties of the material are changed leading to an increase in leakage current and Joule heating. Reversing the polarity of the electric field after every 10⁵ cycles changes the migration direction of oxygen vacancies, thereby preventing charge accumulation at grain boundaries and electrodes. By doing so, the electrocaloric stability is improved and the adiabatic temperature remains constant even after 10⁶ cycles, much higher than achieved in commercially available barium titanate ceramics.     

Ionic conduction,colossal permittivity and dielectric relaxation behavior of solid electrolyte Li3xLa2/3-xTiO3 ceramics

Perovskite-type solid electrolyte lanthanum lithium titanate (LLTO), exhibiting high intrinsic ionic conductivity, has been attracting interests because of its potential use in all solid-state lithium-ion batteries. In this work, we prepared LLTO ceramics by solid state reaction method and studied their conductivity and dielectric properties systematically. It is found that the bulk conductivity of LLTO is several orders of magnitude higher than the grain boundary conductivity. In addition, colossal permittivity was observed in LLTO ceramics in wide frequency/temperature ranges. Two non-Debye type relaxation peaks were observed in the imaginary part of permittivity, resulting from Li⁺ ions motion and accumulation near interfaces of grains/grain boundaries/electrodes. It is suggested that colossal permittivity may originate from the lithium ion dipoles inside the samples and the interfacial polarization of lithium ion accumulation near the grain boundaries. These results clarify the relations among colossal permittivity, relaxation behavior and ionic conduction in solid ion conductor ceramics.     

Optimized strain properties with small hysteresis in BNT-based ceramics with ergodic relaxor state

Electric field-induced high strain with small hysteresis and good temperature stability is necessary for piezoactuators devices. Most of previous works focus on the giant strain achieved in Bi_0.5Na_0.5TiO₃ (BNT)-based ceramics through electric field-induced transition from nonergodic relaxor to ferroelectric state, while the high remnant strain or/and large hysteresis are always accompanying. In this work, through enhancing the local polarization by rare earth ions doping (e.g., La³⁺), we propose to improve the strain properties of BNT-based lead-free ceramics with ergodic relaxor state which displays the near zero remnant strain, small hysteresis, high temperature stability but the low strain value. The addition of La³⁺ would not change the ergodic relaxor state, but can improve the short-range correlation of local polar nanoregions, cut down the critical electric field of transition between relaxor and ferroelectric states, and elevate the electrostrictive effect of ceramics. Finally, high strain of ～0.3 % with low hysteresis of ～8?30 % was obtained in the broad temperature range from room temperature to 100 °C, which is superior to previous BNT-based ceramics and other lead-based/lead-free ceramics. This work affords a paradigm to regulate the ergodic relaxor state to optimize the strain properties, which give the significant guide for strain developments.     

Effect of La substitution on the structural and electrical properties of BaBi4−xLaxTi4O15

Pure and lanthanum doped barium bismuth titanate BaBi_4−xLa_xTi₄O₁₅ (BBLT, x=0, 0.05, 0.15, 0.30) ceramics were prepared utilizing solid state method. The X-ray diffraction (XRD) data confirmed formation of single-phase Aurivillius compounds while SEM micrographs did not show evident grain size change of doped ceramics. Dielectric properties were investigated in 1.21 kHz to 1 MHz frequency range and in the temperature range of 20 to 727 °C. When Bi³⁺ is substituted with La³⁺, a significant disorder was induced and the material exhibited broadening of the phase transition. Impedance analysis confirmed the presence of two semicircular arcs in doped samples suggesting the existence of grain and grain-boundary conduction. The dc-conductivity and activation energies were evaluated for all compositions.     

Effects of loading rate and temperature on domain switching and evolutions of reference remnant state variables during polarization reversal in a PZT wafer

A PZT wafer poled in thickness direction is subject to through-thickness electric field cyclic loads at four different loading rates and four different temperatures. Electric displacement in thickness direction and in-plane extensional strain are measured and plotted during a complete cycle of polarization reversal. Reference remnant polarization and reference remnant in-plane extensional strain are calculated from the measured data. Effects of electric field loading rate and temperature on domain switching process and evolutions of reference remnant state variables are discussed and explained using consecutive two step slow 90° domain switching processes and reduced coercive field at high temperatures.