Barium Zirconate Titanate Ceramics Research Articles

Influence of A-site Gd doping on the microstructure and dielectric properties of Ba(Zr 0.1Ti 0.9)O 3 ceramics

Pure and Gd-doped barium zirconate titanate (BaZr 0.1Ti 0.9O 3, BZT) ceramics were prepared by solid state reaction method. Phase analysis showed the formation of the pyrochlore phase (Gd 2Ti 2O 7) at about 5 mol% Gd doping in BZT. The microstructural investigation on the sintered ceramics showed that Gd doping significantly reduced the grain size of pure BZT ceramics, from about 100 μm to 2–5 μm. Change in the Gd concentration had minor influence on the grain size and on morphology. An increase in the Gd content decreased the Curie temperature ( T C ) of the BZT ceramics. The maximum dielectric constant at T C was observed for 2 mol% Gd and with further increase in Gd content the dielectric constant at T C decreased. The dielectric constant was significantly improved compared to that of pure BZT ceramic. Tunable dielectric materials with good dielectric properties can be prepared by doping BZT with Gd.

MICROSTRUCTURE AND DIELECTRIC PROPERTIES OF BARIUM ZIRCONATE TITANATE CERAMICS BY TWO METHODS

ABSTRACT Barium zirconate titanate (short for BZT) ceramics were prepared by sol-gel method and solid state reaction method, respectively. The BZT ceramics prepared by two methods are both single cubic perovskite phase. The average grain size of the ceramics by sol-gel method is much smaller than that of the ceramics by solid state reaction method, and the shape of grain tends to be spherical. The BZT ceramics with smaller grain size prepared by sol-gel method have the lower Curie temperature and dielectric constant, the higher dielectric loss and the stronger diffuse phase transition than that of the ceramics with larger grain size prepared by solid state reaction method. The coercive electric field of the BZT ceramics prepared by sol-gel method is much more than that of the BZT ceramics prepared by solid state reaction method, while the remanent polarization of the BZT ceramics prepared by sol-gel method is less than that of the BZT ceramics prepared by solid state reaction method.

Ultrawideband dielectric spectroscopy of BaZrxTi1−xO3 ceramics and its microscopic mechanism of polarization

Ultrawideband dielectric spectroscopy analysis of barium zirconate titanate (BaZrxTi1−xO3, BZT) ceramics at different temperatures disclosed the contribution of both the dipole and the ionic polarizations to permittivity at around dielectric maximum temperature (Tm). In BaZr0.25Ti0.75O3 ceramics, the permittivity around Tm is dominated by the temperature dependence of the permittivity determined by the dipole polarization (εdipole). In relaxor ferroelectrics, the diffuse dielectric response around Tm could be derived from the temperature dependence of εdipole. The variation of εdipole with temperature could be also explained by the growth process of polar nanoregions (PNRs) and the damping process of the thermal fluctuation of dipoles in PNRs.

Effects of grain size on domain structure and ferroelectric properties of barium zirconate titanate ceramics

Barium zirconate titanate (BaZr 0.2Ti 0.8O 3, short for BZT) ceramics were prepared by conventional ceramic method, and the effect of grain size on domain structure and ferroelectric properties were studied by XRD, scanning electron microscopy (SEM) and LC material analyzer. It is found that BaZr 0.2Ti 0.8O 3 ceramics is of perovskite crystal structure. As the sintering time increased from 0.5 h to 2 h, 4 h and 8 h, the average grain size of BZT ceramics increased from ∼25 μm to ∼40 μm, ∼45 μm and ∼80 μm. It is shown that the grain size influences on the types of domains of BaZr 0.2Ti 0.8O 3 ceramics, and 90°-domain has not been observed in large grain size sample. Moreover, domains with herribone, lamellar and “water-mark” characters are observed. The coercive electric field decreases and the remanent polarization increases as the grain size of BZT ceramics increases.

Ferroelectric relaxor behaviour and impedance spectroscopy of Bi2O3-doped barium zirconium titanate ceramics

Bi2O3-doped barium zirconate titanate ceramics, Ba1−xBix(Zr0.05Ti0.95)O3, have been prepared by the conventional solid-state reaction method. The ferroelectric relaxor behaviour and dielectric properties have been investigated in detail. By XRD analysis, it is suggested that up to x = 0.04, Bi3+ substitutes A-site ion, and thereafter with higher Bi3+ content, it enters the B-site sub lattice. Substitution of Bi3+ ions induces ferroelectric relaxor behaviour and the degree of relaxation behaviour increases with bismuth concentration. The remanent polarization and strain behaviour show a slight increase with the substitution level. The degree of hysteresis (strain versus electric field) also reduces from 21.4% to 4.6% with bismuth substitution. Impedance measurements were made on the prepared sample over a wide range of temperatures (300–723 K) and frequencies (40 Hz–1 MHz), which show the presence of both bulk and grain boundary effects in the material. The bulk and grain boundary conductivities determined from impedance study indicate the Arrhenius-type thermally activated process. Impedance spectroscopy is shown to be an efficient method capable of detecting the contributions of the resistances of grains and grain boundaries to the complex impedance of a ceramic system, accurately estimating its electrical conductivity as well as its corresponding activation energies and drawing conclusions on its structural properties.

Fabrication of Barium Zirconium Titanate Ceramics Using Ultrasonic Ball Milling Technique

In this work, barium zirconium titanate (BZT) ceramics were fabricated by using a ultrasonic ball milling technique. BZT with the ratio of BaCO3:ZrO2:TiO2 was 1:0.05:0.95 was mixed in ultrasonic ball milling for 1, 3 and 4.5 hr and calcined at temperature of 1000 °C. Phase formation of BZT powder was investigated using XRD technique. Moreover, physical and electrical properties were examined. It was found that the tetragonal structure of BZT can be observed. Particle size of sample powder obtained from new milling technique is smaller than that of powder obtained from conventional mixed oxide method. Moreover, this new technique also requires the less time fabrication. Furthermore, the dielectric properties are increased with milling time and sintering temperature.

Relaxor behavior and dielectric properties of La 2O 3-doped barium zirconium titanate ceramics for tunable device applications

La 2O 3-doped barium zirconate titanate (Ba 1− x La x )Zr 0.2Ti 0.8− x/4 O 3 ceramics have been fabricated by conventional solid-state route. The ferroelectric relaxor behavior and dielectric properties of (Ba 1− x La x )Zr 0.2Ti 0.8− x/4 O 3 ceramics have been investigated. La 3+ ions substitute for A-site Ba 2+ ions to enter the unit cell maintaining the perovskite structure of solid solution and induce the occurrence of ferroelectric relaxor behavior. The temperature dependence dielectric constant and loss reveals that (Ba 1− x La x )Zr 0.2Ti 0.8− x/4 O 3 ceramics have a typical relaxor behavior and diffuse phase transition characteristics and the degree of ferroelectric relaxation behavior is enhanced with the increase of La-dopant concentration. The Curie temperature ( T C) of (Ba 1− x La x )Zr 0.2Ti 0.8− x/4 O 3 ceramics is remarkably shifted to lower temperature with the increase of x. The dielectric loss of (Ba 1− x La x )Zr 0.2Ti 0.8− x/4 O 3 ceramics is obviously improved by La-doping. The appropriate La 2O 3 doped barium zirconate titanate ceramics with suitable dielectric constant, low dielectric loss and high tunability could be attractive materials for tunable ceramic capacitors and tunable microwave device applications.

Dielectric properties and relaxor behavior of rare-earth (La, Sm, Eu, Dy, Y) substituted barium zirconium titanate ceramics

Based on the Ti-vacancy defect compensation model, (Ba1−xLnx)Zr0.2Ti0.8−x∕4O3 (Ln=La,Sm,Eu,Dy,Y) ceramics have been fabricated via the conventional solid-state reaction method. The microstructures, dielectric properties, and ferroelectric relaxor behavior of (Ba1−xLnx)Zr0.2Ti0.8−x∕4O3 ceramics have been investigated. The results indicate that rare-earth ions with various ionic radii enter the unit cell to substitute for A-site Ba2+ ions and inhibit the grain growth. The typical ferroelectric relaxor behavior is induced due to the rare-earth ions substitution. The diffuseness of the phase transition and the degree of ferroelectric relaxor behavior are enhanced, the TC is remarkably shifted to lower temperature, and the tunability is suppressed with the increase of x value and substituted ionic radius for (Ba1−xLnx)Zr0.2Ti0.8−x∕4O3 (x=0.005–0.04, Ln=La,Sm,Eu,Dy,Y) ceramics. Tunable ferroelectric materials with moderate dielectric constant and low dielectric loss can be obtained by manipulating the doping amount of suitable rare-earth ions.

Piezoelectric and Dielectric Properties of (Bi0.5Na0.5)TiO3-Ba(Ti0.95Zr0.05)O3 System

The morphotropic phase boundary of bismuth sodium titanate (BNT) and barium zirconate titanate (BZT) ceramics were study. In the case of (1-x)BNT-xBZT where x = 0.06 to 0.12 mol. The solid solution ceramics which have the combine phases between rhombohedral and tetragonal are obtained at x = 0.06 to 0.11 mol. The maximum of piezoelectric and dielectric constants are obtained for 0.93BNT-0.07BZT ceramics at 161 pC/N and 1839, respectively. This may be indicated that this composition is nearly existed of MPB region.

Dielectric and ferroelectric characteristics of barium zirconate titanate ceramics prepared from mixed oxide method

Barium zirconium titanate (BZT) ceramics were prepared by mixed oxide method. X-ray diffraction showed the presence of a single phase while Raman scattering confirmed structural transitions as a function of different Zr/Ti ratio. The addition of Zr strongly influenced the crystal structure and electrical properties of the ceramics. A typical hysteresis loops were observed for all investigated compositions. BZT ceramics with 15 mol% Zr have shown a ferroelectric to paraelectric transition at around 77 °C.

Observation of high permittivity in Ho substituted BaZr0.1Ti0.9O3 ceramics

The authors observed an extremely high permittivity (∼35000 at TC) in barium zirconate titanate (BaZr0.1Ti0.9O3) ceramics with holmium substitution (1–5mol%) in Ba site. Careful microstructural investigation and energy dispersive spectroscopy analysis of the 1–2mol% of Ho substituted ceramics showed the enrichment of a Ho-phase along the grain boundaries with a composition close to the Ho2Ti2O7 pyrochlore. The formation of Ho rich phase resulted in the Maxwell-Wagner polarization mechanism, which leads to this unusually high permittivity. Ceramics with 3mol% or higher Ho content showed lesser permittivity values compared to 1–2mol%, probably due to the increase in pyrochlore phase. These high dielectric constant ceramics are useful in nanoscale devices.

Dielectric properties and relaxation of Bi-doped (Pb 0.75Ba 0.25)(Zr 0.70Ti 0.30)O 3 ceramics

The strong influence of bismuth additions to the lead–barium–zirconate–titanate ceramics of Ba/Zr/Ti 25/70/30 composition on grain structure, dielectric properties and dc conductivity is confirmed. The Bi-modified ceramics exhibit classical relaxor ferroelectrics (RF) behaviour similar to the other lead containing perovskites such as lead–lanthanum–zirconate–titanate-type ceramics. Dielectric relaxation typical for the ferroelectric relaxors is observed in the vicinity of diffuse ferroelectric–paraelectric phase transition. Additional anomalies in ε ′ ( T) curves in the low frequency range, present in the paraelectric phase for the undoped ceramics, are eliminated by the Bi admixture which also reduces the dc conductivity by three orders of magnitude. A qualitative explanation of the experimental results is presented in the paper.

Effect of Nb doping on the relaxor behaviour of (Pb 0.75Ba 0.25)(Zr 0.70Ti 0.30)O 3 ceramics

Strong influence of niobium admixture added to the lead–barium–zirconate–titanate ceramics of a chosen composition Ba/Zr/Ti 25/70/30 on grain structure, dielectric, and pyroelectric properties was confirmed. The Nb-modified ceramics exhibit classical relaxor ferroelectric behaviour similar to other complex lead perovskites such as lead–lanthanum–zirconate–titanate-type ceramics. Additional anomalies in ɛ′( T) curves in low frequency range were observed in the paraelectric phase for undoped ceramics. These anomalies and some disturbances in regularities typical for the relaxor ferroelectric behaviour in the vicinity of diffuse ferroelectric–paraelectric phase transition in undoped PBZT ceramics are eliminated by the Nb admixture. An attempt at a quantitative explanation is presented in the paper.

Charge Compensation in ZnO-Ln<sub>2</sub>O<sub>3</sub> Co-Doped Barium Zirconate Titanate Ceramics

Charge Compensation in ZnO-Ln<sub>2</sub>O<sub>3</sub> Co-Doped Barium Zirconate Titanate Ceramics

Ferroelectric characteristics of ytterbium-doped barium zirconium titanate ceramics

Ferroelectric characteristics of ytterbium-doped barium zirconium titanate (BZT in brief) ceramics have been investigated. It is found that ytterbium dopant greatly influences the dielectric properties of BZT ceramics. With the increase of ytterbium content, the Curie temperature is lowered by three apparent stages identified by the falling “rate”, and the relative permittivity maximum is enhanced and broadened enormously. The diffuseness of the ferroelectric phase transition for BZT is increased monotonously as well. The A/B ratio in perovskite structure plays another important role on the ferroelectric phase transition characteristics for ytterbium doped BZT. The alternation of the substitution preference of ytterbium ions for the host cations in perovskite lattice seems to account for these effects. Thanks to the modifications of ytterbium on BZT, we developed a novel Y5V dielectric material with the room temperature dielectric constant over 23,000, and the dielectric strength higher than 4.0 kV/mm under AC field, which can be used in manufacturing high voltage ceramic capacitors.

The effect of Sm2O3-dopant on the microstructure and dielectric properties of BaZrxTi1-xO3 ceramics

The effect of Sm2O3-dopant on the microstructure and dielectric properties of barium zirconium titanate ceramics has been investigated. It has been discovered that trace Sm2O3-dopant in barium zirconium titanate ceramics could greatly affect the dielectric and sintering behaviour. With the increase of Sm2O3 in BaZr0.15Ti0.85O3, the Curie point will shift to lower temperature, and the relative permittivity reach to a maximum of more than 23,000 at the content of 0.75wt%. SEM observations show that there exists a crisis content of 0.05wt%, below that the increasing Sm2O3-dopant will promote the densification of barium zirconium titanate ceramics during sintering, while above that the increasing dopant content will depress the densification of the ceramics with the dopant content less than 0.1wt%. More Sm2O3-dopant than 0.1wt% can facilitate the grain growth and enhance the density again. The substitution of Sm3+ for cations in the perovskite lattice can account for these effects.