Preparation of (Bi1/2K1/2)TiO3-Bi(Mg1/2Ti1/2)O3-BiFeO3 Ceramics Withnanodomain Structure and their Piezoelectric Properties

Lead-free (Bi0.5K0.5)TiO3)-Bi (Mg0.5Ti0.5)O3-BiFeO3 (BT-BMT-BF) ceramics were prepared by a conventional solidstate synthesis. Synchrotron x-ray diffraction studies indicated two compositional phase boundaries. An increased strain of 0.070% was obtained at 50 kV/cm, 1 Hz, 25 °C for one of the phase boundary compositions of 0.45BKT-0.1BMT-0.45BF with the temperature of the dielectric maximum of 331 °C.

Study of Nb-Zn-Mn Co-Doped Ba(Ti,Zr)O3 Ceramics

The surface coating processing technique was utilized to modify hydrothermally synthesized Ba(Zr0.10Ti0.90)O3 (BZT) with Nb-organic compound and Zn-organic compound and Mn-organic in organmetallic precursor (Nb-EDTA and Zn-EDTA and Mn-EDTA), which were coated on the powders uniformly. The sintering temperature was decreased and dense ceramics were obtained with well-developed grain growth at 1300 0 C. With increasing the amount of (Nb2/3Zn1/3) from 0 to 1.3 mol%, the Curie temperature was monotonously lowered from 85 0C to 20 0C. The corresponding dielectric maximum decreased first and then increase. The shift rate of the phase transition point of (Nb2/3Zn1/3) codoped BZT was -48.5 0 C/mol%. With increasing of the amount of Mn, the Curie point temperature was lowered greatly, accompanied by a decrease in the corresponding dielectric maximum and an enhancement of the ferroelectric relaxor characteristic.

Crystal Growth and Electrical Properties of Na0.5Bi0.5TiO3-BaTiO3 Lead-Free Ferroelectric Piezocrystals

(1-x)(Na0.5Bi0.5)TiO3-xBaTiO3 (abbreviated as NBBT100(1-x)/100x or NBBT100x) solid solution single crystals with x=0, 0.06, 0.08, 0.10, 0.20, 1.0 were grown using top-seeded solution growth (TSSG) method. Dielectric, piezoelectric and ferroelectric properties of NBBT crystals were investigated as a function of temperature, frequency, composition and crystal orientation. The temperature (Tm) corresponding to dielectric maximum and the depolarization temperature (Td) decrease with increasing x. The <001> oriented NBBT90/10 single crystal shows excellent piezoelectric performance with piezoelectric constant (d33) value about 275pC/N and exhibits relatively smaller coercive field (Ec) of 2.49 kV/mm and dielectric loss tanδ of 2.9 %, indicating a more adaptive engineered domain structure.

Impedance and Dielectric Properties of Nb-Doped Pb(Zr0.52Ti0.48)O3 Ceramics

The compositions of Pb(Zr0.52Ti0.48)O3 doped with 1-6 mole% Nb content were prepared by a conventional mixed oxide technique. It was found that the phase formed depended on the dopant concentration. At lower concentration, the dominate phase was the tetragonal. With increasing Nb content the rhombohedral phase tended to increase. Furthermore, the Curie temperature (Tc) and dielectric constant decreased with increasing Nb concentration and the dielectric maximum peaks were broadened with more rhombohedral phase presence, causing the diffused ferroelectric-paraelectric phase transition. The impedance of the samples decreased with increasing temperature and it was also observed that the impedance increased with increasing Nb concentration.

Processing and properties of ferroelectric relaxor lead scandium tantalate Pb(Sc1/2Ta1/2)O3 thin films

Thin films of Pb(Sc1/2Ta1/2)O3 (PST) were fabricated using an optimized chemical solution deposition procedure involving the de-hydration of scandium acetate and the addition of up to 30% excess lead in solution. The choice of substrate was found to impact the thermal induced stress in the films as confirmed by wafer bending and in-plane grazing angle x-ray diffraction measurements. The presence of either a compressive or a tensile in-plane stress led to a reduction in the temperature of the dielectric maximum, whereas the value of the dielectric maximum remained relatively unchanged; its value reduced by an order of magnitude compared with ceramic samples. It is concluded that mechanical stress alone is not the sole factor in the reduction of PST thin film permittivity. Microstructural features resulting from processing induced defects or an incomplete transformation to the relaxor state may be responsible for this commonly observed phenomenon.

Size Effect of Dielectric Properties for Barium Titanate Particles and Its Model

Powder dielectric measurement of barium titanate (BaTiO3) fine particles from 17 to 1,000 nm revealed a maximum dielectric constant at a certain particle size. The sizes with maximum dielectric constants were strongly dependent on preparation methods. When BaTiO3 fine particles were prepared in vacuum of 10-2 torr, a dielectric maximum of 15,000 was observed at 70 nm. On the other hand, when BaTiO3 fine particles were prepared in air, a dielectric maximum of 5,000 was observed at 140 nm. Structure refinement of BaTiO3 particles using a Rietveld method revealed that all of BaTiO3 particles were composed of two parts; (a) surface cubic layer and (b) bulk tetragonal layer. Moreover, a thickness of surface cubic layer for BaTiO3 particles prepared in vacuum was much thinner than that for BaTiO3 particles prepared in air. To explain the differences, a new model on the basis of “surface relaxation” was proposed.

Perovskite Stabilization in Pb[(Zn1/3Ta2/3),Ti]O3 with BaTiO3 Substitution and Dielectric Properties

A multiple-octahedral system of Pb ( Zn 1/3 Ta 2/3) O 3- PbTiO 3 was modified by 20 mol% BaTiO3 and perovskite formation tendencies were studied. Crystal symmetries and lattice parameters were determined. Low-frequency dielectric constant spectra and microstructures of the ceramics were examined. A cubic perovskite symmetry changed to tetragonal with increasing fractions of PbTiO3. Dielectric maximum temperatures shifted linearly with the compositional change.

Field Induced Dielectric Properties of 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 Thin Films

ABSTRACTDC electric field induced dielectric properties of 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) thin films were studied as a function of frequency at different temperatures. It was observed that the dielectric constant (ε) and dissipation factor (tanδ) were decreased in presence of bias field. The temperature of dielectric maxima was found to increase with increasing bias level. The low temperature (<Tm) frequency dispersion of dielectric permittivity was suppressed with the application of dc bias. After a certain bias voltage the relaxor property of films was disappeared i.e. the films exhibited normal ferroelectric behavior. Since the absence of long range interaction among the nanopolar clusters in PMN and its family is believed to be the origin of relaxor behavior, disappearance of relaxor nature in PMN-PT (70/30) films could be attributed to manifestation of long-range order at higher bias voltage. This was observed in the temperature dependence of dielectric constant i.e. the films neither exhibited any frequency dispersion in the temperature of dielectric maximum (Tm) nor showed any diffused phase transition. The relaxor property of PMN-PT thin films was studied in terms of diffused phase transition together with frequency dispersion of the temperature of dielectric maximum (Tm). Vogel-Fulcher relation was used to analyze the frequency dependence of temperature of dielectric maximum.