Pitak Laoratanakul

Physical properties and phase transitions in perovskite Pb[Zr1−x(Ni1/3Nb2/3)x]O3 (0.0 ⩽ x ⩽ 0.5) ceramics

A solid solution of lead zirconate–lead nickel niobate ceramics, Pb[Zr1−x(Ni1/3Nb2/3)x]O3 (PZNN) with x = 0.0–0.5, was synthesized via the columbite precursor method. The crystal structures as well as the thermal and dielectric properties were investigated in terms of the lead nickel niobate (PNN) concentration. X-ray diffraction indicated that all samples exhibited a single-phase perovskite structure. At room temperature, Pb[Zr1−x(Ni1/3Nb2/3)x]O3 is orthorhombic for a composition where x = 0, rhombohedral for the compositions where x = 0.1, 0.2 and 0.3 and pseudo-cubic for compositions where x = 0.4 and 0.5. The results of the addition of lead nickel niobate to the lead zirconate ceramic showed enhancement of the room-temperature dielectric permittivity. Lead nickel niobate substitution also led to lower transition temperatures. Furthermore, this transition from normal to relaxor FE ceramics was typified by a quasi-linear relationship between the diffuseness parameter δγ and the PNN mole fraction x.

Dielectric Properties of BaTiO3-Modified BiFeO3 Ceramics

Multiferroic BiFeO3 has attracted extensive interest due to its potential in several applications. However, pure-phase BiFeO3 is very difficult to obtain. Hence, mixing BiFeO3 with other ferroelectrics, such as BaTiO3, is another approach to obtain materials with possible multiferroic properties. In this study, the BiFeO3 was modified with addition of BaTiO3 via a simple solid state reaction method. Dielectric properties of the BaTiO3-modified BiFeO3 ceramics were investigated over wide range of temperature and frequency. The results show that the (1-x)BiFeO3-xBaTiO3 ceramics with x = 0.1 and 0.2 exhibited large dielectric properties with giant-dielectric-like behavior. The dielectric properties were seen to improve with increasing BaTiO3 content, with the highest dielectric constant (ϵr = 19000) observed in 0.8BiFeO3-0.2BaTiO3 ceramic. The results were explained in terms of the pre-dominantly intrinsic BiFeO3 giant-dielectric behavior as a result of Fe multivalent states, as well as a better grain packing density with increasing BaTiO3 content.

Dielectric properties improvement of polymer composite prepared from poly(vinylidene difluoride) and barium-modified porous clay heterostructure

Significant improvements in dielectric properties of poly(vinylidene difluoride) (PVDF) can be achieved by adding small amounts of barium-modified porous clay heterostructure (Ba-PCH). In this article, composite films of PVDF with various amounts of Ba-PCH were fabricated by the compression method. SEM images indicated good dispersion of Ba-PCH in the PVDF matrix, as island-like particles caused improvement in the mechanical and thermal properties in the composite films. The films were highly heat resistant between 446°C and 452°C, depending on the amount of Ba-PCH added. The addition of Ba-PCH in the PVDF matrix reduced the non-polar phase, α-phase, of the PVDF, which resulted in the presence of a polar-phase, β-phase. There was a decrement of the non-polar phase of PVDF after adding small amounts of Ba-PCH, the dielectric constant (at 1 kHz) was dramatically increased from 6.0 of the neat compressed PVDF film to 34.1, 44.8, 47.1, and 56.0 of the compressed PVDF film with 3 wt. %, 5 wt. %, 7 wt. %, and 10 wt. % of Ba-PCH in the PVDF matrix, respectively.

Dielectric Properties Enhancement in Polybenzoxazine Composite at Multi-Frequency Range

This research proposed a novel nano barium strontium titanate (BST) powder- polybenzoxazine composite as a new dielectric material. In this work, the dielectric properties of a surface-treated BST powder-polybenzoxazine composite were studied. The surface of the BST powders were modified by using three different chemicals: 3-aminopropyl-trimethoxysilane, benzoxazine monomer and phthalocyanine. The distribution of the BST powders in the polybenzoxazine matrix was observed by SEM. The dielectric constants of the composites with a function of frequency (1 kHz–10 MHz) were investigated. It was found that the composites with modified BST powders showed good distribution in the polybenzoxazine matrix, and the dielectric constants were also much enhanced than those with untreated BST powders. In comparisons among the three modification methods, the composite with the silane coupling modified BST powder showed significantly in dielectric constant improvement while the composite with the benzoxazine and phthalocyanine modified BST powders displayed lower dielectric loss due to the modified powder dispersed well in the polybenzoxazine matrix.

Effect of Rice Husk Ash to Mechanical Properties of Clay Bricks

This research explored the effect of rice husk ash on the mechanical properties of clay bricks, for example, strength, density, and water absorption. Rice husk ash, varying 0 to 5% by weight, was added. The results showed that porosity increased when adding rice husk. Adding 3% rice husk ash by weight showed the best mechanical brick properties, with 13.50 MPa of compressive strength, 1.69 g/cm3 of density, and 11.50% of water absorption.

Surface-Modified Porous Clay Heterostructure Synthesized by Introduction of Cationic Ions: Effects on Dielectric Behavior

The dielectric enhancement of solid state materials was easily leading by adding the small amount of cationic ion in processing step. In this work, porous clay heterostructure (PCH) derived from bentonite was doped with various cationic solutions. The cationic-modified PCHs were characterized by SEM, BET and Zeta potential. The result suggested that metal ion was trapped into mesoporous structure of PCH, leading to the localized cationic charge along modified clay structure. Thus, the dielectric properties were enhanced. It can be noted that cationic-modified PCH would be one candidate material as excellent filler for dielectric properties enhancement in polymer based nanocomposite.

Induced internal bubble shapes affected piezoelectric behaviors of PVDF films

Poly (vinylidene fluoride), Piezoelectric, Dielectric constant, Microporous PVDF films, Bubble shapes.

Effect of Calcination Conditions on Phase Formation and Characterization of BiFeO3-BaTiO3 Powders Synthesized by a Solid-State Reaction

A perovskite-type phase of solid solution of BiFeO3-BaTiO3 powders were synthesized by a solid-state reaction via a rapid vibro-milling technique. The effect of calcination condition on the phase formation, and characterization of BiFeO3-BaTiO3 powders were investigated. The formation of the BiFeO3-BaTiO3 phase investigated as a function of calcination conditions by TG–DTA and XRD. Morphology, particle size and chemical composition have been determined via a combination of SEM and EDX techniques and vibrating sample magnetometer (VSM) was used to characterize the structures and magnetic properties of prepared samples. The rapid vibro-milling is employed for the first time in this work as a significant time-saving method to obtain single-phase BiFeO3-BaTiO3 powders.

Effects of Dopants on Phase Formation and Microstructure of Bismuth Sodium Titanate-Potassium Sodium Niobate Ceramics

In this work, the solid solution of (0.93)(Bi0.5Na0.5)TiO3-(0.07)(K0.5Na0.5)NbO3 ceramics were prepared by a conventional mixed-oxide method. The influence of 0.5 mol% MnO2, Sb2O5 and Li2O3 addition on phase formation, microstructure and dielectric properties of BNT-KNN has been investigated. It was found that the BNT-KNN ceramics exhibited the perovskite structure with pseudo-cubic symmetry. The microstructure showed grain shape depending additive; the pure BNT-KNN the round shape grains were seen, while with the oxide additive square or rectangular shape grains appeared. The oxide addition into BNT-KNN ceramics resulted in the difference dielectric properties and Curie temperatures.

Preparation of Lead Zirconate-Lead Nickel Niobate Ceramics by the Reaction Sintering Process

The perovskite structure of lead zirconate – lead nickel niobate ceramics, (1-x) PbZrO 3 –xPb(Ni 1/3 Nb 2/3 )O 3 (PZ – PNN) at x between 0.00–0.50, has been prepared by the reaction-sintering process. The specimens were prepared directly from a mixture of their constituent oxide without any calcination step. The PZ – PNN ceramics could be obtained after 6 h sintering at 1,100–1,250°C. Crystal structure and phase transition of PZ-PNN were investigated by x-ray diffraction (XRD). XRD indicated that the structure of PZ-PNN ceramics is orthorhombic for a composition where x = 0.00, rhombohedral for compositions where x = 0.10 ≤ x ≤ 0.40 and pseudo-cubic for a composition where x = 0.50. The dielectric properties of the ceramics were measured as functions of both temperature and frequency. The results indicated that the transition temperature decreases with increasing PNN concentration. Furthermore, morphology and grain size evolution have been determined via a scanning electron microscope (SEM)