Morphotropic Phase Research Articles

Low electric field induced high energy storage capability of the free-lead relaxor ferroelectric 0.94Bi0.5Na0.5TiO3-0.06BaTiO3-based ceramics

Morphotropic phase (MPB) eco-friendly ferroelectric 0.94Bi0.5Na0.5TiO3- 0.06BaTiO3 (NBT-BT) ceramics exhibits superior piezoelectric performances. However, the large remnant polarization (Pr) and low breakdown strength (Eb) of NBT-BT systems hinders application in energy storage capacitors. Herein, the Bi(Zn1/3Nb2/3)O3 (BZN) is selected to partially replace the NBT-BT ceramics to break ferroelectric long-range order domains achieving higher energy storage properties. Highly recoverable energy storage density (Wrec ~ 3 J/cm3) and efficiency (η ~ 75%) are acquired in (NBT-BT)-0.06BZN ceramics under a low applied electric field of 210 kV/cm. Furthermore, superior temperature stability (20–120 °C), and frequency (1–1000 Hz) stability, and fatigue endurance (105 st) are also gained. These advantages further suggest that the (NBT-BT)-0.06BZN ceramics exhibit great promise in pulsed power markets.

Dielectric and ferroelectric properties of K2Pb4Nb10O30–Na2Pb4Nb10O30–K6W4Nb6O30 across morphotropic phase region

Ferroelectric ceramics of K2Pb4Nb10O30–Na2Pb4Nb10O30–K6W4Nb6O30 (abbreviated to KPN–NPN–KWN) were synthesized by using a high-temperature solid-state reaction technique. Phase structure, dielectric and ferroelectric properties of the ceramics with composition passing across the morphotropic phase (MP) region in the phase diagram were mainly investigated. Temperature dependence of dielectric constant (ɛ(T)) of KPN–NPN–KWN solid solutions with 30, 50 and 60-mol% NPN were investigated in detail. All samples were characterized by a broad dielectric maximum peak of ɛ(T) at the Curie temperature and weak frequency dielectric dispersion. All compositions exhibited classical diffuse phase transition of a relaxor ferroelectric with a broad peak of dielectric constant induced by the compositional disorder. The K1.36Na1.2Pb3.44W0.56Nb9.44O30 ceramic located on the line 60-mol% NPN in the region of rhombic phase in the vicinity of the MP-region exhibited a high dielectric constant (ɛ∼9700) at 1kHz near the Curie temperature.

Dynamic hysteresis and scaling behavior for Pb(Zr,Ti)O3 ceramics

The dynamic hysteresis of Nb-doped Pb(ZrxTi1−x)O3 (PZT, 0.40 ≤ x ≤ 0.60) ceramics with different phase structures was investigated as functions of frequency f and electric field amplitude E0. When E0 grows over ∼1.5 times of coercive field Ec, all the loops become well saturated and their scaling relations of hysteresis area ⟨A⟩ against f and E0 can be expressed with an identical form as ⟨A⟩∝f0.01E00.10 for either tetragonal phase or morphotropic phase, which is in good agreement with our previous result of rhombohedral PZT [Chen et al., J. Appl. Phys. 114, 244101 (2013)]. The results indicate that ferroelectrics with fairly distinct domain structures could have similar dynamic hysteresis and scaling behavior at high-E0 region.

Frequency Dependence of Coercive Field in Soft Pb(Zr1−xTix)O3 (0.20 ≤ x ≤ 0.60) Bulk Ceramics

Frequency (f) dependence of coercive field (Ec) of six Pb(Zr1−xTix)O3 (0.20 ≤ x ≤ 0.60) bulk ceramics with different compositions was investigated at various frequencies (1–100 Hz). Scaling relations of Ec against f, Ec ∝ fβ, were obtained, where the value of exponent β varied with the ceramics composition. These exponents were far smaller than that of the theoretic prediction because the domain wall motion played a major role in the frequency region. In addition, the values of the exponents were of obvious discrepancy for different phase structures with tetragonal, rhombohedral, and morphotropic phases, but nearly similar for the same phase structure with different compositions, suggesting that different domain structures influence the scaling behaviors.

Composition Dependent Dielectric Anomaly in Na1−xKxNbO3, at x = 0.475

Sodium-potassium niobate (Na1−xKxNbO3) pellet samples, with x = 0.40, 0.47, 0.475, 0.48 and 0.50, were prepared by solid state reaction method. With varying composition (x), X-ray diffraction patterns show a break in the peak shifting tendency, at x = 0.475. Lattice parameters calculated from X-ray diffraction patterns show a slope change anomaly, in the a/b vs. x plot, from positive to negative, at x = 0.475. Dielectric constant, loss tangent and dielectric conductivity were found minimum for the composition with x = 0.475, among the prepared compositions, at all measured frequencies and temperatures. The observed results show a strong compositional dependence of dielectric properties, in this system. Observed minimum values of dielectric parameters may be associated with increased Na site vacancies and structural anomaly- a morphotropic type phase transition, at the composition with x = 0.475.

Preparation of complex oxide thin films under hydrothermal and hydrothermal-electrochemical conditions

Thin-film growth of complex oxides including BaTiO3, SrTiO3, BaZrO3, SrZrO3, KTaO3, and KNbO3 were studied by the hydrothermal and the hydrothermal-electrochemical methods. Hydrothermal-electrochemical growth of ATiO3 (A = Ba, Sr) thin films was investigated at temperatures from 100° to 200°C using a three-electrode cell. Current efficiency for the film growth was in the range from ca. 0.6% to 3.0%. Tracer experiments revealed that the ATiO3 film grows at the film/substrate interface. AZrO3 (A = Ba, Sr) thin films were also prepared on Zr metal substrates by the hydrothermal-electrochemical method. By applying a potential above ca. +2 V vs. Ag/AgCl to the Zr substrates, AZrO3 thin films were formed uniformly. KMO3 (M = Ta, Nb) thin films were prepared on Ta metal substrates by the hydrothermal method. Perovskite-type KTaO3 thin films were formed in 2.0 M KOH at 300°C. Pyrochlore-type K2Ta2O6 thin films were formed at lower temperatures and lower KOH concentrations. Morphotropic phase changes were also revealed in the hydrothermal system KTaO3-KNbO3.

열에이징에 의한 PZT세라믹스의 내열특성 개선

Temperature stabilities of resonance frequencies of the substrates are very important in piezoelectric ceramics oscillators and fitters. In this study, it was investigated thermal resisting property of the length-extensional vibration mode of PZT ceramics. The mode can be utilized in fabricating ultra-small 55 kHz IF devices. We fabricated the ceramic specimens with x = 0.51, 0.52, 0.53, 0.54, and 0.55 in the Pb(Zr<TEX>$\sub$</TEX>x/Ti<TEX>$\sub$</TEX>1-x/)O<TEX>$_3$</TEX> system. And their resonance frequencies were measured before 1st thermal aging, after 1st and 2nd thermal aging. In order to investigate the influence of thermal aging on thermal resisting properties, thermally aged specimens were once mote thermally aged. Before 1st thermal aging, the specimens of the compositions with morphotropic phase, x = 0.53 and rhombohedral phase, x = 0.54 have weak thermal resisting property of resonance frequency, while tetragonal phase, x = 0.51 has robust thermal resisting property of resonance frequency. 1st thermal aging improved thermal resisting property of resonance frequency in all specimens.

PLZT Ferroelectric Ceramics on the Morphotropic Boundary Phase. Study as Possible Pyroelectric Sensors

PLZT compositions near the morphotropic boundary phase (Zr/Ti = 53/47) were studied changing the lanthanum fraction from 0.5 to 14 at%. The grain size and the porosity due to the lanthanum addition showed an important influence on the dielectric properties of the samples. Dielectric and pyroelectric studies show that the ceramics of lower lanthanum concentrations are suitable materials for practical applications. The ceramic's response subjected to light radiation was investigated. The radiation is absorbed near the material surface and its temperature rises leading to a change in the electrical polarization of the bulk material. This phenomenon is analyzed and correlated with the absorbed light on the surface of the material.

PbTiO 3 buffer layer effects on the structural and electrical properties of Pb(Zr, Ti)O3 thin films grown by sputtering on silicon substrates

Pb(Zr, Ti)O 3 (PZT) thin films have been grown on Si/SiO2 and Si/SiO2/Ti/Pt substrates by rf magnetron sputtering and the effects of PbTiO3 (PT) buffer layers to the structural and electrical properties of PZT films were studied. The PT buffer layers were grown in situ (without postannealing) with thicknesses ranging from 100 to 1200 Å. The PT layer orientation can be adjusted by the deposition temperature. The PZT films with a composition near the morphotropic phase (54/46) were deposited at room temperature followed by a conventional postannealing treatment. The disappearance of cracks in PZT films deposited on Si/SiO2/PT substrates indicates the role of the buffer layer as a stress absorber. By using a PT buffer layer it was possible to control the PZT films’ orientation. Polycrystalline PZT films without a buffer layer changed to highly (100) or (111) oriented films, depending on the preferred orientation of the buffer layer. The influence of the buffer layer thickness and the PZT films’ orientation on the electrical properties was also investigated.

Sound wave velocity and tawfik percentage of Nb doped PZT transducers

Abstract When small amounts of niobia are added to lead titanate zirconate with composition Pb(Zr0.54Ti0.46)O3 near the morphotropic (tetragonal–rhombohedral) phase boundary, the modified ceramics show different densities and different ranges of piezoelectric resonance frequency. Ceramic materials have been obtained where the cation stoichiometry has been adjusted to allow for charge compensation of the donor ions by Pb vacancies. The Tawfik percentage of 0.8 wt % Nb is a particular composition to obtain high piezoelectric among the crystallites. This is attributed to residual 180° domains after poling. For ′ < 0.8 wt % Nb, a high-frequency resonator can be obtained. Particular attention is also given to the properties of water in the ocean, which limit the propagation of underwater sound to be used for radar.