Piewpan Parjansri

Phase Formation, Dielectric and Ferroelectric Properties of Mn, Al Doped BCZT Ceramics by Molten Salt Method

Lead-free Ba(1-x)CaxZr0.1Ti0.9O3 (x = 0.15) ceramics doped with 0.00–0.20 mol% MnO2 and Al2O3 were prepared by the molten salt method. The powder was ball-milled for 24 h and then calcined at 1000°C for 4 h and sintered at 1300°C for 2 h. The phase formation and dielectric properties of the ceramic systems were analyzed by X-ray Diffraction (XRD) and electrical measurement. The phase of the samples showed pure perovskite structure for all conditions. The BCZT ceramics doped with MnO2 and Al2O3 exhibited a dielectric properties. BCZT doped with Mn has a higher dielectric constant than BCZT doped with Al. The loss tangent values at 1 kHz were lower than 0.02 of all samples. The ceramic systems indicate ferroelectric behavior for all samples (Pr ∼ 1.25–2.26 μC/cm2and Ec ∼ 3.10–4.25 kV/cm).

Effect of Zn2+ and Nb5+ Co-doping on electrical properties of BCZT ceramics by the seed-induced method

The effects of Zn2+ and Nb5+ co-doping (x mol%ZN) on the electrical properties of lead-free Ba0.90Ca0.10Zr0.10Ti0.90O3-Seed ceramic systems, where x = 0.0–1.0 mol% have been studied. The ceramics were prepared using the solid state reaction technique. The phase of the samples showed pure perovskite structure. The density values of the ceramics were in the range of 4.86–5.78 g/cm3. The maximum dielectric constant was 40893 for 0.8 mol% ZN. The highest values of Pr ∼ 5.85 μC/cm2, d33 ∼ 381 pC/N and kp ∼ 38% were obtained for the sample of 0.4 mol% ZN.

Effects of Mn and Sr Doping on the Electrical Properties of Lead-Free 0.92BCZT-0.08BZT Ceramics

The effects of Mn and Sr doping on the electrical properties of lead-free 0.92[(Ba0.85Ca0.15Zr0.1Ti0.9)O3]-0.08[(BiZn0.5Ti0.5)O3] ceramics have been studied. A-site and B-site doping with 0.00–0.05 mol% of SrCO3 and 0–0.25 mol% of MnO2 was performed. The ceramics were prepared using the solid state reaction technique. The powder was ball-milled for 24 h, then calcined at 1,000ºC for 4 h and sintering at 1,300ºC for 2 h. Phase formation and microstructure of ceramics were examined using an x-ray diffractometer (XRD) and scanning electron microscopy (SEM). All samples have a single phase of perovskite structure. Grain size and density value were in the range of 3.43–4.07μm and 5.78–5.83 g/cm3, respectively. The electrical properties of the ceramics were investigated as a function of Mn and Sr doping. It was found that the dielectric constant, activation energy and ac conductivity change with the dopant. Moreover, Mn and Sr doping lead to a decrease of dielectric loss, lower than 0.003 for all samples (at 1 kHz).

Effect of Particle Sizes of BaTiO3 (BT) Seed on Microstructure and Electrical Properties of (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3

The study was conducted to find out the effect of particle sizes of BaTiO3 (BT) seed on the microstructure and electrical properties of (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 (BCZT) ceramics. The BT seeds were prepared by the molten salt method. Results indicated that the BT seed powder showed a single pure perovskite phase when using a low temperature of ~750°C. The particle sizes of BT seeds increased from ~381 to ~600 nm with increasing heating temperatures from 750 to 900°C. After that, the different BT seeds were mixed with BaCO3, CaCo3, ZrO2 and TiO3 via the solid state reaction method. The mixed powder was calcined and sintered at 1200 °C for 2 h and 1450 °C for 4 h, respectively. The microstructure, phase formation and electrical properties were investigated. All ceramic samples showed a pure perovskite phase. The density and average grain size values of ceramics were in the range of 5.36-5.47 g/cm3 and 9.83-11.86 μm, respectively. The highest values of dielectric constant (εr), piezoelectric constant (d33) were 3393 and 452 pC/N, respectively which obtained at the sample of BT-seed size 372 nm doped.

Effects of B-site doping on piezoelectric and ferroelectric properties of Pb0.88Sr0.12(Zr0.54Ti0.44Sb 0.02)(1-y)-(Zn1/3Nb2/3) yO3 ceramics

Pb0.88Sr0.12(Zr0.54Ti0.44Sb0.02)(1-y) – (Zn1/3Nb2/3)yO3 ceramics where y = 0.00–0.10 were prepared by a solid state reaction method. Doping of Zn and Nb (co-doped) at B-site produced a phase transformation from tetragonal to rhombohedral phase. Highest piezoelectric coefficient d33 of 632 pC/N was recorded for the y = 0.04 sample. The piezoelectric result was correlated with the phase formation and the ferroelectric properties. Dielectric constant and loss tangent slightly increased with increasing the co- doped content. However, loss tangent values were less than 0.06 for all samples. These results indicated that the piezoelectric and dielectric properties of the ceramics could be improved by the co-doping.

Effects of BaTiO3 doped on structural and dielectric properties of Bi0.5(Na0.80K0.20)0.5TiO3 ceramic

ABSTRACT We studied the effects of BaTiO3 (BT) seed nano-crystals on dielectric properties and phase transition behavior of Bi0.5(Na0.8K0.2)0.5TiO3 (BNKT) ceramics. The BaTiO3 seed nano-crystals were used as nuclei, which acted as templates for starting materials to form perovskite phase. In this study, the BT seed nano-crystals were prepared by the molten salt technique. Eutectic mixtures of NaCl-KCl (1:1 by mole) were used as the flux. Various concentrations of BT seed nano-crystals were mixed with other precursors required for formation of BNKT phase, which was prepared by the solid-state method. Addition of BT seed nano-crystals enhanced the electrical properties of ceramics. The sample with 8 mol% BT seed nano- crystals exhibited highest value of dielectric constant (ϵr) at maximum temperature of 6700. The grain size significantly decreased with increasing concentration of BT seed nano-crystals. The relaxor ferroelectric behavior was also observed with the diffuseness parameter (γ) value being close to 2.

Phase Structure, Microstructure and Electrical Properties of BCZT Ceramics Prepared by Seed-Induced Method

The effect of particle sizes of CaZrO3 (CZ) nanocrystal on the phase structure, microstructure and electrical properties of Ba0.85Ca0.15Zr0.10Ti0.90O3 (BCZT) was studied. The CaCO3 and ZrO2 were used as starting materials for CaZrO3 (CZ) seeds synthesized by the molten-salt method. The results were found that the CZ powder has a pure perovskite with the particle size about 370 to 460 nm. Then the CZ nanocrystals were mixed with the metal oxides BaCO3, CaCO3, ZrO2 and TiO2 by mixed oxide method. The phase structure, microstructure and electrical properties of BCZT ceramic were investigated as a function of particle size and concentration of CZ. The results indicated that all samples showed pure perovskite phase. The highest values of density, grain size, dielectric constant (εr) and piezoelectric coefficient (d33) were 5.50 g/cm3, 10.95 μm, 2992 and 446 pC/N, respectively which obtained at the CZ seed size 459 nm.

Effects of NaNbO3 Crystals on Electrical Properties of K0.5Na0.5NbO3 Ceramics

Lead-free (K0.5Na0.5)NbO3 (KNN) piezoelectric ceramics were studied and synthesized by the seed-induced method. NaNbO3 crystal was used as seed and prepared by molten salt synthesis (MSS). The average particles size of NaNbO3 seed crystal was about 1-3 mm. Then, the NaNbO3 seed was mixed with KNN powder and ball milled for 24 h. The mixed powder was calcined at 700-900 °C and sintered at 1100 °C. The phase structure and morphology of the ceramics were investigated by X-ray diffraction and scanning electron microscope and the electrical properties were studied. The results indicated that all samples showed a pure perovskite phase. The highest density of the ceramic was 93% compared to the theoretical density. The results showed that NaNbO3seed crystal improved piezoelectric properties of KNN ceramics.

The Electrical Properties of BCZT Lead-Free Ceramics Induced by BaZrO3 Seeds

Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) ceramics were produced by using the seed-induced method. The nano-particle BZ (BaZrO3) seeds were mixed with BaCO3, CaCO3, ZrO2 and TiO2 powder for preparing by the mixed oxide method. The XRD results indicated that all powder and sintered ceramic samples showed a pure perovskite phase with coexistence between rhombohedral and tetragonal phase. As the BZ seed content increased, the density of ceramics tended to decrease from 5.61 g/cm3 to 5.37 g/cm3. The average grain size of the ceramics was in the range of 12.15 -13.50 mm. The dielectric loss (tand) was less than 0.03 for all samples at room temperature (at 1 kHz). Other electrical properties, including dielectric constant (εr), remnant polarization (Pr), and piezoelectric charge coefficient (d33) values decreased with increasing BZ seed doping with relates to the decreasing grain size and density of BCZT ceramics. However, the values of coercive field (Ec) decreased and piezoelectric voltage coefficient (g33) increased with BZ seed doping.

Electrical properties of (1−x)BCZT-xBZT lead-free ceramics

The aim of this study was to investigate the electrical properties of (1-x)[Ba0.85Ca0.15Zr0.1Ti0.9]O3 - x[(BiZn0.5Ti0.5)O3] ceramics system for x = 0.00 - 0.10. The (1-x)BCZT-xBZT ceramics were fabricated via solid state reaction technique. The samples were calcined and sintered at 925°C for 6 h and 1370°C for 3 h, respectively. Phase formation and microstructure of (1-x)BCZT-xBZT ceramics were studied using an X-ray diffractometer (XRD) and scanning electron microscope (SEM). The physical properties and electrical properties, such as dielectric properties and ferroelectric properties were examined. It was found that all the samples show pure perovskite phase. The BZT content lead to the change and improved of the dielectric properties of ceramic samples. The dielectric loss values were lower than 0.01 (at 1 kHz) for all samples. The samples show higher degree of the relaxor like behavior with higher BZT content. In addition, the ferroelectric properties were found to depend on the BZT content.