Anucha Watcharapasorn

Enhanced dielectric, ferroelectric, and electrostrictive properties of Pb(Mg1/3Nb2/3)0.9Ti0.1O3 ceramics by ZnO modification

The effects of ZnO modification on the dielectric, ferroelectric, and electrostrictive properties of 0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 (PMNT) ceramics are systematically studied in this work. The PMNT/xZnO (with x = 0, 0.4, 2.0, 4.0, and 11.0 mol. %) ceramics of complex perovskite structure were prepared by solid state reaction and sintering process. It is found that the maximum value of the dielectric constant decreases with increasing ZnO amount up to x = 4.0 mol. %, and then significantly increases with x = 11.0 mol. %. The temperature of maximum dielectric constant tends to increase, while the diffuseness of the dielectric peak is reduced, with increasing ZnO content. The remanent polarization and the coercive field increase with increasing ZnO concentration. The induced strain and the electrostrictive coefficient reach the maximum values of 0.10% (at E = 10 kV/cm) and 12.94 × 10−16 m2/V2, respectively, with x = 2.0 mol. % ZnO. The ceramic doped with a high ZnO content (11.0 mol. %) exhibits a macroscopic...

Crystal structure and electrical properties of bismuth sodium titanate zirconate ceramics

Lead-free bismuth sodium titanate zirconate (Bi0.5Na0.5Ti1-xZrxO3 where x = 0.20, 0.35, 0.40, 0.45, 0.60, and 0.80 mole fraction) [BNTZ] ceramics were successfully prepared using the conventional mixed-oxide method. The samples were sintered for 2 h at temperatures lower than 1,000°C. The density of the BNTZ samples was at least 95% of the theoretical values. The scanning electron microscopy micrographs showed that small grains were embedded between large grains, causing a relatively wide grain size distribution. The density and grain size increased with increasing Zr concentration. A peak shift in X-ray diffraction patterns as well as the disappearance of several hkl reflections indicated some significant crystal-structure changes in these materials. Preliminary crystal-structure analysis indicated the existence of phase transition from a rhombohedral to an orthorhombic structure. The dielectric and ferroelectric properties were also found to correlate well with the observed phase transition.

ELECTRICAL AND MECHANICAL PROPERTIES OF PZT/PVDF 0-3 COMPOSITES

Granules of in-house prepared PZT ceramic and powder of commercially available PVDF polymer were used as starting materials to form a series of xPZT/(1 - x)PVDF composites (where x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1.0) with 0–3 connectivity. Densities of the composites tended to increase with increasing PZT ceramic content. Phase and microstructure of the composites revealed homogeneous mixture between PZT and PVDF phases. The composites with higher ceramic content had higher dielectric constant and dielectric loss tangent. Ferroelectric measurement revealed the effect of PZT phase connectivity in 0.9PZT/0.1PVDF ceramic in which a sudden jump in ferroelectric properties was observed. Mechanical properties in terms of hardness, Youngs modulus and fracture toughness were also improved when PZT content was increased.

Investigation of a new lead-free Bi0.5(Na0.40K0.10)TiO3-(Ba0.7Sr0.3)TiO3 piezoelectric ceramic.

Lead-free piezoelectric compositions of the (1-x)Bi0.5(Na0.40K0.10)TiO3-x(Ba0.7Sr0.3)TiO3 system (when x = 0, 0.05, 0.10, 0.15, and 0.20) were fabricated using a solid-state mixed oxide method and sintered between 1,050°C and 1,175°C for 2 h. The effect of (Ba0.7Sr0.3)TiO3 [BST] content on phase, microstructure, and electrical properties was investigated. The optimum sintering temperature was 1,125°C at which all compositions had densities of at least 98% of their theoretical values. X-ray diffraction patterns that showed tetragonality were increased with the increasing BST. Scanning electron micrographs showed a slight reduction of grain size when BST was added. The addition of BST was also found to improve the dielectric and piezoelectric properties of the BNKT ceramic. A large room-temperature dielectric constant, εr(1,609), and piezoelectric coefficient, d33 (214 pC/N), were obtained at an optimal composition of x = 0.10.

Influences of phase transition and microstructure on dielectric properties of Bi0.5Na0.5Zr1-xTixO3 ceramics

Bismuth sodium zirconate titanate ceramics with the formula Bi0.5Na0.5Zr1-xTixO3 [BNZT], where x = 0.3, 0.4, 0.5, and 0.6, were prepared by a conventional solid-state sintering method. Phase identification was investigated using an X-ray diffraction technique. All compositions exhibited complete solubility of Ti4+ at the Zr4+ site. Both a decrease of unit cell size and phase transition from an orthorhombic Zr-rich composition to a rhombohedral crystal structure in a Ti-rich composition were observed as a result of Ti4+ substitution. These changes caused dielectric properties of BNZT ceramics to enhance. Microstructural observation carried out employing SEM showed that average grain size decreased when addition of Ti increased. Grain size difference of BNZT above 0.4 mole fraction of Ti4+ displayed a significant increase of dielectric constant at room temperature.

Effect of ZnO Nano-Particulates on Structure and Properties of PZT/ZnO Ceramics

In this research, effect of ZnO nano-particles on structure, mechanical and electrical properties of PZT ceramics was investigated. X-ray diffraction result suggested that tetragonality of PZT decreased with increasing ZnO content. Density tended to increase with an addition of ZnO while grain size of the ceramics decreased. An addition of ZnO increased hardness of the ceramics. Maximum hardness was achieved at an addition of 0.5 wt% ZnO. Within the PZT/ZnO ceramics, increasing content of ZnO gradually increased fracture toughness. Electrical properties characterization of the ceramics showed that an addition of ZnO reduced dielectric constant and slightly lowered Curie temperature. Ferroelectric measurement found that an addition of < 0.5 wt% ZnO did not significantly change ferroelectric properties. However, these properties were degraded at higher content of ZnO.

Effects of ZnO nanoparticulate addition on the properties of PMNT ceramics

This research was conducted in order to study the effect of ZnO nanoparticulate addition on the properties of 0.9 Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 [PMNT] ceramics. The PMNT ceramics were prepared by a solid-state reaction. The ZnO nanoparticles were added into PMNT ceramics to form PMNT/x ZnO (x = 0, 0.05, 0.1, 0.5, and 1.0 wt.%). The PMNT/x ZnO ceramics were investigated in terms of phase, microstructure, and mechanical and electrical properties. It was found that the density and grain size of PMNT ceramics tended to increase with an increasing amount of ZnO content. Moreover, a transgranular fracture was observed for the samples containing ZnO, while pure PMNT ceramics showed only a intergranular fracture. An addition of only 0.05 wt.% of ZnO was also found to enhance the hardness and dielectric and ferroelectric properties of the PMNT ceramics.

Fabrication of Bi0.5Na0.5ZrO3 Powder by Mixed Oxide Method

Lead-free bismuth sodium zirconate powder with formula Na0.5Bi0.5ZrO3 was prepared by conventional mixed oxide method. Bismuth sodium zirconate (BNZ) powder with 10wt%Na2CO3 was calcined at 800 °C for 2 h dwell time. Investigation of the effects of re-calcination and dwell time on phase formation of powders was also carried out. The results revealed that re-calcination significantly affected the formation of single-phase BNZ powder. Phase characteristics were checked by X-ray diffraction (XRD). Powder Cell software was employed to simulate crystal structure of BNZ powder. It was found that BNZ powder most likely possessed an orthorhombic structure. SEM result showed its average particle size was 0.47 mm and composition measured EDX correlated with theoretical composition of BNZ.

Effect of composition on electrical properties of lead-free Bi0.5(Na0.80K0.20)0.5TiO3-(Ba0.98Nd0.02)TiO3 piezoelectric ceramics

Lead-free piezoelectric ceramics with the composition of (1−x)Bi0.5(Na0.80K0.20)0.5TiO3-x(Ba0.98Nd0.02)TiO3 or (1−x) BNKT-xBNdT (with x = 0–0.20 mol fraction) have been synthesized by a conventional mixed-oxide method. The compositional dependence of phase structure and electrical properties of the ceramics were systemically studied. The optimum sintering temperature of all BNKT-BNdT ceramics was found to be 1125 °C. X-ray diffraction pattern suggested that BNdT effectively diffused into BNKT lattice during sintering to form a solid solution with a perovskite structure. Scanning electron micrographs showed a slight reduction of grain size when BNdT was added. It was found that BNKT-0.10BNdT ceramic exhibited optimum electrical properties (er = 1716, tanδ = 0.0701, Tc = 327 °C, and d33 = 211 pC/N), suggesting that this composition has a potential to be one of a promising lead-free piezoelectric candidate for dielectric and piezoelectric applications.

Effects of Dy Substitution for Bi on Phase, Microstructure and Dielectric Properties of Layer-structured Bi4-xDyxTi3O12 Ceramics

Bi4-xDyxTi3O12 (when x = 0, 0.25, 0.5, 0.75 and 1.0) powders and ceramics were prepared by solid-state mixed oxide method. The calcination was carried out at 900°C for 4 h with heating/cooling rate 5°C/min. The ceramics were then sintered at a temperature between 950–1100°C for 4 hrs. The optimum sintering temperature was found to be 1000°C. X-ray diffraction indicated the existence of orthorhombic phase for all sintering temperatures. Scanning electron micrographs of ceramic surfaces showed a plate-like structure with different grain size. The results of room temperature dielectric constant revealed that Dy dopant could dielectric constant of Bi4Ti3O12 ceramic where it was optimized at x = 0.25.