Dielectric,ferroelectric, and piezoelectric properties of Sb2O3-modified (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 lead-free ceramics

The microstructures, phase structure, and electrical properties have been investigated for the Sb₂O₃-modified (Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃ lead-free piezoelectric ceramics. The grain size was strongly affected by Sb₂O₃, and the solid solutions show a single phase perovskite structure. The ceramics with x = 0.1 % exhibit enhanced electrical properties of d ₃₃ ～556 pC/N, k _p ～52 %, ε _r ～3,895, tan δ ～1.3 %, and P _r ～12.6 μC/cm² when sintered at a low temperature of ～1,350 °C. The high temperature stability of ferroelectric properties (P _r ～14.8 μC/cm²) was obtained in the temperature range from ?60 to 0 °C. And with the addition of small amount of Sb₂O₃, Curie temperature (T _c ) maintains virtually unaltered.     

Improved energy storage and electrocaloric properties of lead-free Ba0.85Ca0.15Zr0.1Ti0.9O3 ceramic

Lead-free Ba_0.85Ca_0.15Zr_0.1Ti_0.9O₃ (BCZT) ceramic powders were synthesized using the sol–gel method. The ceramics thickness was reduced to achieve high-energy storage and large electrocaloric effect in bulk ceramics. Dielectric, ferroelectric, energy storage, and electrocaloric properties were investigated for BCZT ceramic with 400 µm. Here, pure crystalline structure and homogenous microstructure were identified by XRD analysis and SEM measurements, respectively. The dielectric measurements revealed a maximum dielectric constant associated with ferroelectric–paraelectric phase transition. The maximum of \(\varepsilon^{\prime}_{{\text{r}}}\) was 17841, around 352 K. Furthermore, the BCZT ceramic exhibited improved energy storage and electrocaloric properties. A high recoverable energy density W_rec of 0.24 J/cm³ and a total energy density W_total of 0.27 J/cm³ with an efficiency coefficient of?~?88% at 423 K under an electric field of 55 kV/cm were obtained. Besides, The maximum value of ΔT?=?2.32 K, the electrocaloric responsivity ζ?=?0.42 K mm/kV, the refrigeration capacity RC?=?4.59 J/kg and the coefficient of performance COP?=?12.38 were achieved around 384 K under 55 kV/cm. The total energy density W_total and the temperature change ΔT were also calculated by exploiting the Landau–Ginzburg–Devonshire (LGD) theory. The theoretical results matched the experimental findings. These results suggest that the synthesized BCZT ceramic with reduced thickness could be a promising candidate for energy storage and electrocaloric applications.

     

Structural, dielectric and electrical properties of Pb(SnTi)O3 ferroelectric system

We have synthesized (PST) with x=0.45, 0.55, 0.65 ferroelectric ceramics by a solid-state reaction technique and performed preliminary X-ray diffraction (XRD) analysis and the temperature and frequency dependence dielectric measurements on them. The a.c. and d.c. conductivities have been investigated over a wide range of temperature and the activation energy have also been calculated. It is observed that: (i) the relative dielectric permittivity () and loss tangent (tan ) are dependent on frequency, (ii) the temperature of dielectric permittivity maximum shifts toward lower temperature side, (iii) permittivity maximum decreases with the increase of Sn content in the (PST) compounds and (iv) no frequency dispersion of the dielectric permittivity reveals the no-relaxor behavior of the materials.     

Effect of Zr on dielectric, ferroelectric and impedance properties of BaTiO3 ceramic

A polycrystalline sample of Zr-doped barium titanate (BaTiO₃) was prepared by conventional solid state reaction method. The effect of Zr (0·15) on the structural and microstructural properties of BaTiO₃ was investigated by XRD and SEM. The electrical properties (dielectric, ferroelectric and impedance spectroscopy) were measured in wide range of frequency and temperature. With substitutions of Zr, the structure of BaTiO₃ changes from tetragonal to rhombohedral. Lattice parameters were found to increase with substitution. The room temperature dielectric constant increases from ～ 1675 to ～ 10586 and peak dielectric constant value increases from ～ 13626 to ～ 21023 with diffuse phase transition. Impedance spectroscopy reveals the formation of grain and grain boundary in the material and found to decrease with increase in temperature.     

Effects of La-doping on microstructure, dielectric and piezoelectric properties of Ba0.85Ca0.15Ti0.90Zr0.10O3 lead-free ceramics

Lead-free (Ba_0.85Ca_0.15)_1?xLa_2/3xTi_0.90Zr_0.10O₃ + 1 mol% MnO₂ ceramics have been prepared an ordinary sintering technique and the effects of La-doping on the microstructure, dielectric and piezoelectric properties of Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃ were studied. All the ceramics possess a pure perovskite structure, indicating that La ions are incorporated into Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃ lattices to form a lead-free solid solution. The ceramics are transformed from coexistence of orthorhombic and tetragonal phases to pseudocubic phase with the doping level of La increasing. After the doping of La, grain growth is inhibited, ferroelectric-paraelectric phase transition temperature (T _C) is decreased and the degree of diffuse phase transition is increased. The ferroelectricity of the ceramics is weakened after the addition of La. Unlike donor-doped lead zirconate titanate ceramics, the piezoelectric properties of the ceramics are degraded after the partial substitution of La³⁺ for (Ba_0.85Ca_0.15)²⁺ because of the weakness or disappearance of coexistence of orthorhombic and tetragonal phases near room temperature. The (Ba_0.85Ca_0.15)_1?xLa_2/3xTi_0.90Zr_0.10O₃ + 1 mol% MnO₂ ceramic with x = 0 exhibit the optimum piezoelectric properties: d ₃₃ = 277 pC/N and k _p = 30.3 %, respectively.     

Structural, dielectric and electrical properties of Sm-modified Pb(SnTi)O3 ferroelectric system

We have synthesized (Pb_1-xSm_x)(Sn_yTi_1-y)_1-x/4O₃ (PSmST) polycrystalline ferroelectric ceramics with x = 005, 007, 01 and y = 0.45 by a solid-state reaction technique and performed preliminary X-ray diffraction (XRD) analysis, detailed temperature and frequency dependence dielectric measurements on them. The a.c. conductivity has been investigated over a wide range of temperature and the activation energy (E _a.c) has also been calculated. It is observed that (i) the dielectric permittivity (e) and loss tangent (tan °) are dependent on frequency, (ii) the temperature of dielectric permittivity maximum shifts toward lower temperature side with the increase of samarium ion (Sm₃) concentration at the Pb sites, and (iii) observed and calculated d-values of XRD patterns show that the compounds have been formed in orthorhombic single phase.     

The study of CoFe2O4/Ba0.85Ca0.15Zr0.1Ti0.9O3-laminated composite ceramic on dielectric,relaxation, ferroelectric,and magnetoelectric coupling properties

Journal of Materials Science: Materials in Electronics - In this work, pure Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) and CoFe2O4 (CFO) ceramics were prepared by the sol–gel and co-precipitation...     

Sintering temperature-induced electrical properties of (Ba0.90Ca0.10)(Ti0.85Zr0.15)O3 lead-free ceramics

Effects of the sintering temperature on the microstructure and electrical properties of (Ba_0.90Ca_0.10)(Ti_0.85Zr_0.15)O₃ (BCTZ) lead-free piezoelectric ceramics have been studied, where these ceramics were prepared by the conventional oxide-mixed method at varied sintering temperatures from 1300 °C to 1500 °C. These BCTZ ceramics exhibits a phase transition from a rhombohedral phase to the coexistence of rhombohedral and tetragonal phases with an increase of sintering temperature. With an increase of sintering temperature, their relative density and average grain size gradually increase, and electrical properties are improved greatly. These BCTZ ceramics sintered at ～1440 °C have optimum electrical properties: d₃₃ ～ 442 pC/N and k_p ～ 48.9%, making it a promising material for lead-free piezoelectric ceramics.     

Substrate effect on in-plane dielectric and microwave properties of Ba(Sn0.15Ti0.85)O3 thin films

The microstructure and in-plane dielectric and microwave properties of Barium tin titanate Ba(Sn_0.15Ti_0.85)O₃ (BTS) thin films grown on (1 0 0) LaAlO₃ and (1 0 0) MgO single-crystal substrates through sol–gel process were investigated. X-ray diffraction and field emission scanning electron microscopy were used to characterize crystal structure of phases and microstructure of the thin films, respectively. Microwave properties of the films were measured from 1 to 10 GHz by the interdigital capacitor configuration. The obvious differences in the dielectric and microwave properties are attributed to the stress in the films, which result from the lattice mismatch and difference in the thermal expansion coefficients between the film and substrates. This work clearly reveals the highly promising potential of BTS films for application in tunable microwave devices.     

Effects of MnO2 and sintering temperature on microstructure, ferroelectric, and piezoelectric properties of Ba0.85Ca0.15Ti0.90Zr0.10O3 lead-free ceramics

Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃ + xmol% MnO₂ lead-free ceramics have been prepared by a conventional sintering method and the effects of MnO₂ and sintering temperature on microstructure, ferroelectric, and piezoelectric properties of Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃ lead-free ceramics have been studied. The addition of 0.25 mol% MnO₂ promotes grain growth, improves the ferroelectricity of the ceramics and strengthens ferroelectric tetragonal–ferroelectric orthorhombic phase transition near 40 °C. Because of the coexistence of tetragonal and orthorhombic phases and the combinatory effects of soft and hard doping of Mn ions, the ceramic with x = 0.25 exhibits the optimum piezoelectric properties (d ₃₃ = 306 pC/N and k _p = 42.2 %, respectively). Excess MnO₂ inhibits the grain growth and degrades the ferroelectric and piezoelectric properties of the ceramics. Sintering temperature has an important influence on the microstructure, tetragonal–orthorhombic phase transition near 40 °C, ferroelectric and piezoelectric properties of the ceramics. The increase in sintering temperature leads to large grains and more noticeable tetragonal–orthorhombic phase transition near 40 °C, enhances ferroelectricity and thus improves effectively the piezoelectricity of the ceramics. The Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃ ceramic sintered at 1350 °C possesses the optimum piezoelectric constant d ₃₃ value of 373 pC/N.     

Thickness-dependent dielectric and electrocaloric properties of Pb0.85La0.1(Zr0.85Ti0.15)O3 antiferroelectric thin films on stainless steel substrates

Journal of Materials Science: Materials in Electronics - Pb0.85La0.1(Zr0.85Ti0.15)O3 (PLZT) antiferroelectric (AFE) thin films with different thicknesses were prepared by the sol–gel method...     

Study of structural,impedance spectroscopy and dielectric properties of Li and Al co-doped Ba0.85Ca0.15Ti0.9Zr0.1O3 ceramics

Journal of Materials Science: Materials in Electronics - In this work, we investigate the effect of lithium and aluminium co-doping (0, 0.1, 0.2, and 0.3 mol%) on the phase formation,...     

Multiferroic and fatigue behavior of BiFe(0.95)Mn(0.05)O3/Bi(0.90)La(0.10)Fe(0.85)Zn(0.15)O3 bilayered thin films

Bilayered thin films consisting of BiFe(0.95)Mn(0.05)O(3) (BFMO) and Bi(0.90)La(0.10)Fe(0.85)Zn(0.15O3) (BLFZO) layers were prepared on Pt-coated silicon substrates without any buffer layers by RF sputtering. The (110) orientation was induced with a high phase purity for all bilayers as a result of the introduction of the bottom (110)-oriented BLFZO layer. The low leakage current density of BFMO/BLFZO bilayers could be attributed to a combined effect of the BFMO and BLFZO layers. The dielectric constant increases, the remanent polarization decreases, and the coercive field slightly increases with increasing thickness of the BLFZO layer in BFMO/BLFZO bilayers. Magnetic properties in BFMO/BLFZO bilayers are improved by increasing the BFMO layer thicknesses. A large polarization value of 2Pr ~ 189.5 μC/cm2 is obtained for the BFMO/ BLFZO bilayer with a thickness ratio of 3:1, which is much larger than those reported for BFO-based single layers or multilayers, and a good fatigue behavior is demonstrated with an increase in measurement frequencies and driving electric fields.     

Synthesis, impedance and dielectric properties of LaBi5Fe2Ti3O18

The compound, LaBi₅Fe₂Ti₃O₁₈, is a five-layered material belonging to the family of bismuth layered structure ferroelectromagnetics. D.c. and a.c. conductivity measurements were performed on the samples. Dielectric measurements were also performed on these samples. Combined impedance and modulus plots were used as tools to analyse the sample behaviour as a function of frequency. Cole-Cole plots showed non-Debye relaxation.     

Low temperature sintering and properties of lead-free (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 ceramics with Ba(Cu0.5W0.5)O3 addition

The low-temperature sintering behavior of (Ba_0.85Ca_0.15)(Zr_0.10Ti_0.90)O₃ (BCZT) piezoelectric ceramics with Ba(Cu_0.5W_0.5)O₃ (BCW) addition has been investigated. The addition of 0.1 wt% BCW promotes the sinterability of BCZT ceramics owing to the generation of a liquid phase, resulting in a reduction of sintering temperature from 1,540 to 1,350 °C. The piezoelectric coefficient (d ₃₃), and the electromechanical coupling factor (kp) of the BCZT ? 0.1 wt%BCW specimen sintered at 1,350 °C were 555 pC/N and 55 %, respectively, while Curie temperature (Tc) increases from 85 to 95 °C.