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.     

PZT-nickel ferrite and PZT-cobalt ferrite comparative study: Structural,dielectric, ferroelectric and magnetic properties of composite ceramics

Comparative study of different PZT-based composite materials ((x)PbZr_0.52Ti_0.48O₃ + (1-x)CoFe₂O₄ and (x)PbZr_0.52Ti_0.48O₃ +(1-x)Ni_0.7Zn_0.3Fe₂O₄ (x = 0.8 and 0.9)) is presented in the frame of structural, dielectric, ferroelectric and magnetic properties. PZT and NZF/CF powders were synthesized by auto combustion technique. The composites were synthesized by mixing the appropriate amount of individual phases using conventional sintering. XRD data indicated the formation of well crystallized structure of PZT and NZF/CF, without the presence of undesirable phases. SEM micrographs revealed a uniform grain distribution of both, ferroelectric and ferromagnetic phases. Non-saturated hysteresis loops are evident in all samples due to the existence of non-ferroelectric ferrite phase. All the samples exhibit typical ferromagnetic hysteresis loop, indicating the presence of the order magnetic structure. Dielectric investigations revealed that ferrites are the main source of charge carriers, which must be of electronic origin. The activation energy of effective electrical resistivity is heavily influenced by the ferroelectric phase.     

Insight for the construction of R-T phase boundary in KNN piezoceramics from the view of energy band structure and electron density

The crystal structures and associated energy band structures of classic lead-based PZT (PbZr_0.5Ti_0.5O₃) and lead-free KNN (K_0.5Na_0.5NbO₃) piezoelectric ceramics prepared by a solid-state method are systematically studied based on the First-principles calculations. For better understanding relations between energy band structures and the phase structures in the PbZr_0.5Ti_0.5O₃ and KNN, the components PT (PbTiO₃)/PZ (PbZrO₃) and KN (KNbO₃)/NN (NaNbO₃) are also calculated. The results suggest that the vital contribution to R-T morphotropic phase boundary (MPB) in PbZr_0.5Ti_0.5O₃ comes from the hybridization of A-site and B-site ions, which causes stretching and tilting of oxygen octahedron and therefore leads to the formation of R and T phases. The KNN behaves differently. Moreover, it's concluded that the band structure highly inherited from tetragonal PbTiO₃ plays an important role in the construction of the R-T phase boundary according to the comparison of PbZr_0.5Ti_0.5O₃ and KNN. In general, the work inspires an idea from the view of energy band structure to realize R-T phase coexistence as well as improved piezoelectric properties in KNN-based lead-free piezoceramics.     

Large electrocaloric strength in the (100)-oriented relaxor ferroelectric Pb[(Ni1/3Nb2/3)0.6Ti0.4]O3 single crystal at near morphotropic phase boundary

Relaxor ferroelectric Pb[(Ni_1/3Nb_2/3)_0.6Ti_0.4]O₃ (PNNT) single crystal with composition close to the morphotropic phase boundary (MPB) was successfully prepared using the molten salt method. The analysis results of XRD and TEM indicated that the as-grown crystal is of almost pure perovskite phase with coexistence of tetragonal and rhombohedral. Typical relaxor behavior was observed when the crystal was aged. Large electrocaloric strength (ΔT/ΔE) of 44.97 mK cm/kV was obtained near the phase transition temperature of paraelectric to ferroelectric, indicating that PNNT is a promising material for application in cooling system. Moreover, it is found that the aging of point defects may make an important contribution to the electrocaloric performance of the single crystal, in addition to the contribution of the transition of phases induced by the electric field.     

Dielectric constants of bulk ferroelectric PZT measured by terahertz time-domain spectroscopy

The complex permittivity of bulk ceramic ferroelectric of nominal composition PbZr_0.4Ti_0.6O₃ was measured in the range 0.2–2?THz using transmission time-domain spectroscopy. The results indicate strong absorption and dispersion in this frequency range as often seen in highly disordered and polar materials. The results are compared to equivalent thin film data in the literature, and significant differences in the real and imaginary permittivity suggest that substrate clamping and degree of polarisation of the ferroelectric thin film materials affect dielectric properties even at these high frequencies.     

Structure and properties of Bi(Zn½Ti½)O3-modified Pb(Zr,Ti)O3 piezo-/ferroelectric ceramics around the ternary morphotropic phase boundary

To develop high-performance piezo-/ferroelectric materials, Bi(Zn_½Ti_½)O₃–PbZrO₃–PbTiO₃ (BZT–PZ–PT) ternary solid solution with compositions around the morphotropic phase boundary (MPB) is synthesized by solid-state reaction. The crystal structure and electric properties are investigated systematically by X-ray powder diffraction (XRD), dielectric spectroscopy, and ferroelectric and piezoelectric measurements. On the basis of the results of the XRD, dielectric and ferroelectric measurements, the pseudo-binary phase diagram of the yBi(Zn_½Ti_½)O₃–(1 − y)[(1 − x)PbZrO₃–xPbTiO₃] system has been constructed for three series, namely, y = 0.05, 0.10, and 0.15. It is found that the introduction of BZT into the PZT system makes the paraelectric to ferroelectric phase transition more diffuse, brings the MPB to a lower PT content, and enlarges the MPB region. The best properties with an improved dielectric constant ε' = 1248, and a large remnant polarization P_r = 33 μC/cm², as well as a relatively high T_C = 286°C, and a high coercive field E_c = 23 kV/cm was achieved in the y = 0.15 series with MPB composition x = 0.425, making it a promising material for high-power piezoelectric applications.     

Influences of Liquid‐Phase Sintering on Structure,Grain Growth,and Dielectric Behavior of PbZr0.52Ti0.48O3 Ceramics

In this work, to formulate piezoceramic systems such as PbZr_0.52Ti_0.48O₃ (PZT) for low‐temperature co‐fired ceramic (LTCC)‐based devices, liquid‐phase sintering approach is demonstrated. ZnO–B₂O₃ (ZB) binary glass system is used as sintering aid. X‐ray diffraction (XRD) study confirms the formation of morphotropic phase boundary (MPB; tetragonal + rhombohedral) in PZT prepared by hydrothermal route. ZB is found to induce change in tetragonal/rhombohedral ratio in MPB of PZT. 1%ZB in PZT is found to raise the tetragonality from 71% to 92% in MPB region of PZT. ZB addition in PZT has reduced the sintering temperature from 1250 to 825°C for relative density about 91% with sustaining MPB phase. 1% ZB content is optimal percentage to enhance sinterability and relative density. Uniform dispersion of glass in PZT matrix is confirmed by SEM images. ZB content in PZT is found to controlling grain growth during sintering. Highest dielectric constant and lowest dielectric loss with low sintering temperature (825°C) of 1%ZB among all glass added in PZT exhibit technical suitability of 1%ZB + PZT to use as LTCC‐based energy storage devices.     

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.     

High‐energy storage density and excellent temperature stability in antiferroelectric/ferroelectric bilayer thin films

The antiferroelectric/ferroelectric (PbZrO₃/PbZr_0.52Ti_0.48O₃) bilayer thin films were fabricated on a Pt(111)/Ti/SiO₂/Si substrate using sol‐gel method. PbZr_0.52Ti_0.48O₃ layer acts as a buffered layer and template for the crystallization of PbZrO₃ layer. The PbZrO₃ layer with improved quality can share the external voltage due to its smaller dielectric constant and thinner thickness, resulting in the enhancements of electric field strength and energy storage density for the PbZrO₃/PbZr_0.52Ti_0.48O₃ bilayer thin film. The greatly improved electric breakdown strength value of 2615 kV/cm has been obtained, which is more than twice the value of individual PbZr_0.52Ti_0.48O₃ film. The enhanced energy storage density of 28.2 J/cm³ at 2410 kV/cm has been achieved in PbZrO₃/PbZr_0.52Ti_0.48O₃ bilayer film at 20°C, which is higher than that of individual PbZr_0.52Ti_0.48O₃ film (15.6 J/cm³). Meanwhile, the energy storage density and efficiency of PbZrO₃/PbZr_0.52Ti_0.48O₃ bilayer film increase slightly with the increasing temperature from 20°C to 120°C. Our results indicate that the design of antiferroelectric/ferroelectric bilayer films may be an effective way for developing high power energy storage density capacitors with high‐temperature stability.     

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 PMN modification on structure and electrical response of xPMN–(1−x)PZT ceramic systems

The structural and electrical properties of xPb(Mg_1/3Nb_2/3)O₃–(1−x)Pb(Zr,Ti)O₃ ternary ceramic system with the composition near to the morphotropic phase boundary (MPB) and of xPb(Mg_1/3Nb_2/3)O₃–(1−x)Pb(Zr_0.47Ti_0.53)O₃ ceramics were investigated as a function of the Pb(Mg_1/3Nb_2/3)O₃ (PMN) content by scanning electron microscopy (SEM), X-ray diffraction (XRD), dielectric and piezoelectric spectroscopy and polarization-electric field measurement technique. Studies were performed on the samples prepared by a columbite precursor method for x=0.125, 0.25 and 0.5. Room temperature SEM investigations revealed common trends in the grain structure with increasing PMN content. XRD analysis demonstrated that with increasing PMN content in xPb(Mg_1/3Nb_2/3)O₃–(1−x)Pb(Zr_0.47Ti_0.53)O₃, the structural change occurred from the tetragonal to the pseudocubic phase at room temperature. Changes in the dielectric and ferroelectric behavior were then related to these structural trends and further correlated with the piezoelectric properties. The results of ferroelectric hysteresis measurements, in conjunction with dielectric spectroscopy, demonstrated an intermediate, relaxor-like behavior between normal and relaxor ferroelectrics in the solid solution system, depending on the PMN content.     

Spherical ferroelectric PbZr0.52Ti0.48O3 nanoparticles with high permittivity: Switchable dielectric phase transition with temperature

The spherical ferroelectric PbZr_0.52Ti_0.48O₃ (PZT 52/48) nanoparticles are prepared via simple and environment friendly high temperature solid state method. The crystal structure and morphology of these particles are characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), and field emission scanning electron microscopy (FESEM). XRD analysis and selected area electron diffraction (SAED) pattern of PZT particles revealed its crystalline nature. The energy involved in the synthesis especially during the initiation and termination processes for the formation of PZT particles is found from the high temperature calorimetric study. These particles are spherical in nature with an average diameter of ≤20 nm. The bulk and surface chemical composition of these particles are investigated by Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). XPS study reveals that the prepared PZT particles contain titanium ion in two different oxidation states namely Ti³⁺ and Ti⁴⁺. The PZT particles exhibit high permittivity with relatively low dielectric loss. From temperature dependent dielectric analysis, it is seen that there is a switchable dielectric phase transition at or above 80 °C.     

Synthesis of pyrochlore free PMN-PT powder by partial oxalate process route

Pyrochlore phase free PMN-PT powder of morphotrophic phase boundary (MPB) composition has been prepared using the partial oxalate method. The synthesis process has been optimized by thorough characterization of the intermediate compounds such as columbite and (Mg_1/3Nb_2/3)_0.675 Ti_0.325)O₂ by XRD analysis, particle size analysis, surface area measurement and morphological studies. Lead oxalate produced by in situ precipitation in a suspension of (Mg_1/3Nb_2/3)_0.675Ti_0.325)O₂ powder expected to coat on the particle surface, which improved the homogeneity of the precursors and resulted in the formation of pure PMN-PT phase during calcination at 750 °C. The PMN-PT powder contains more than 95% submicron particle with D₅₀ 0.4 μm. The process eliminates the formation of detrimental pyrochlore phase from the PMN-PT powder.     

Effect of sol composition on dielectric and ferroelectric properties of PZT composite films

Crack free calcium modified PZT composite films have been synthesized using modified sol-gel process by depositing the slurries prepared by mixing powder of composition PbZr_0.52Ti_0.48O₃ and sol of composition Pb_(1−x)Ca_xZr_0.52Ti_0.48O₃ (where x = 0, 0.06, 0.1) on Pt(1 1 1)/Ti/SiO₂/Si substrate. The infilteration process has also been employed which resulted in dense microstructure of the films. Thickness of the films as measured by SEM of cross section of the films was more than 25 μm. The XRD patterns of the resultant films consisted of pure perovskite phase and no peak related to either pyrochlore phase or Pt substrate was observed. The room temperature dielectric constant and loss were compared. The temperature dependence of dielectric constant revealed that T_C of all the films was same, i.e., 351 °C, in spite of different compositions of the sol used. Well saturated PE-loops of the films show that the films were ferroelectric in nature.     

Effect of tungsten doping on the dielectric response of PZN–PT–BT ceramics with the morphotropic phase boundary composition

In this paper, effect of tungsten doping on the dielectric property of the Pb(Zn_1/3Nb_2/3)O₃–BaTiO₃–PbTiO₃ system around morphotropic phase boundary(MPB) composition is presented. Samples were prepared according to the formula Pb_0.85−xBa_0.15[(Zn_1/3Nb_2/3)_0.7Ti_0.3]_1−xW_xO₃ assuming the compensation for W is achieved via the appearance of the lead vacancies. X-ray diffraction results show that a nearly complete perovskite phase was maintained as W was progressively added up to 5 wt.%. Introduction of W stabilizes the tetragonal phase against the rhombohedral one, resulting in the displacement of MPB composition region towards relaxor end. Moreover, lattice distortion of the tetragonal phase is enlarged, that of the rhombohedral phase is lowered. W- doping leads to an increase in the dielectric permittivity maximum and a decrease in the phase transition temperature (T_m). The frequency dispersion of T_m is succesively weakened as W ions are gradually incorporated, reflecting the strengthened couplings among ferroactive oxygen octahedra. A maximum on the degree of diffuse phase transition is observed at 1 mol% WO₃, which can be interpreted in terms of competing effects of chemical inhomogeneity and ferroelectric couplings. W-doping also induces an increase in the tendency towards Curie–Weiss behavior above T_m, which is associated with the growth of ferroelectric domains.     

Morphotropic phase boundary and electrical properties of lead-free (K0.5Bi0.5)TiO3–Bi(Ni0.5Ti0.5)O3 relaxor ferroelectric ceramics

Lead-free relaxor ferroelectric ceramics (1?x)(K_0.5Bi_0.5)TiO₃–xBi(Ni_0.5Ti_0.5)O₃ were prepared by a conventional solid-state route, the phase transition behavior and corresponding electrical properties were investigated. A typical morphotropic phase boundary (MPB) between rhombohedral and tetragonal ferroelectric phases was identified to be in the range of 0.05<x<0.07 where the optimum piezoelectric and electromechanical properties of d₃₃=126 pC/N and k_P=18% were achieved. Most importantly, a high Curie temperature ~320 °C, around which the material shows a typical relaxor ferroelectric behavior characterized by the presence of diffuse phase transition and frequency dispersion, was obtained in MPB compositions, significantly higher than those of some existing MPB lead-free titanate systems. These results demonstrate a tremendous potential of the studied system for device applications.     

The PZT system (PbZr1-xTixO3, 0.0≤x≤1.0): Specific features of recrystallization sintering and microstructures of solid solutions (Part 1)

This work is concerned with the specific features of sintering of solid solutions of the PZT system (PbZr_1?xTi_xO₃, 0.0≤x≤1.0) depending on composition. The microstructure of the solid-solution ceramics has been found to be a fairly homogeneous, mosaic, sufficiently close packing of isometric crystallites with a range of section from 3 to 11 μm, but there exists a number of special features related to the component and phase composition of the objects. It has been found that the changes in multifractal parameters of grain structure of these ceramics reflect with high sensitivity the processes of phase transformations in the solid solutions. The obtained results are useful in developing piezoelectric materials based on the PZT system.     

Microstructure and Optical Property in an Irregular Multilayer Comprising Ferroelectric and Paraelectric Materials

A special sequence of multilayer, consisting of PbZr_0.5Ti_0.5O₃ and SrTiO₃ films, was fabricated using a simple chemical solution deposition. X‐ray diffractometer (XRD) measurement reveals that each film in this multilayer has been crystallized into the single perovskite phase. The high‐angle annular dark‐field scanning transmission electron microscopy (STEM) image shows that the obtained SrTiO₃/PbZr_0.5Ti_0.5O₃ multilayer contains three components with different optical thicknesses: dense and porous PbZr_0.5Ti_0.5O₃ layers, together with dense SrTiO₃ layers. This multilayer system exhibits superior optical performance, with a peak reflectivity of～95% and a bandwidth of ～113 nm, rendering its promising candidate as dielectric mirrors, optical cavities, and selective filters.     

Temperature dependence of field‐responsive mechanisms in lead zirconate titanate

An electric field loading stage was designed for use in a laboratory diffractometer that enables in situ investigations of the temperature dependence in the field response mechanisms of ferroelectric materials. The stage was demonstrated by measuring PbZr_1?xTi_xO₃ (PZT) based materials—a commercially available PZT and a 1% Nb‐doped PbZr_0.56Ti_0.44O₃ (PZT 56/44)—over a temperature range of 25°C to 250°C. The degree of non‐180° domain alignment (η₀₀₂) of the PZT as a function of temperature was quantified. η₀₀₂ of the commercially available PZT increases exponentially with temperature, and was analyzed as a thermally activated process as described by the Arrhenius law. The activation energy for thermally activated domain wall depinning process in PZT was found to be 0.47 eV. Additionally, a field‐induced rhombohedral to tetragonal phase transition was observed 5°C below the rhombohedral‐tetragonal transition in PZT 56/44 ceramic. The field‐induced tetragonal phase fraction was increased 41.8% after electrical cycling. A large amount of domain switching (η₀₀₂=0.45 at 1.75 kV/mm) was observed in the induced tetragonal phase.