Jerapong Tontrakoon

The study of dielectric diffuseness in the Ba(Mg1/3Nb2/3)O3?BaTiO3 ceramic system

The dielectric properties of Ba(Mg1/3Nb2/3)O3 (BMN)-substituted BaTiO3 (BT) (xBMN–(100−x)BT) ceramics, where x = 0–5 mol%, were prepared by a high-temperature solid-state reaction technique. It was found that the substitution of Mg2+ and Nb5+ at the Ti-site of the BMN–BT ceramics caused compositional inhomogeneity, leading to a diffuse phase transition (DPT). Discontinuous grain growth accompanied with excellent dielectric diffuseness was found in 3–5 mol% BMN specimens. The maximum solubility limit of Mg/Nb substitution was assumed to be between 3 2 mol%, the maximum dielectric constant decreased and the Curie temperature shifted downwards on the lower temperature side.

Dielectric properties and microstructure of CaCu3Ti4-xMnxO12 ceramics

In this work, we have reported the dielectric properties and microstructure of the Mn doped CaCu3Ti4O12 (CCTO) ceramics. The conventional solid-state reaction was employed. By the partial Mn -for Ti substitution, the dielectric loss was suppressed remarkably while the dielectric constant (¿r) still remains high. The sample CaCu3Ti3.76Mn0.24O12 exhibits a high ¿r over 1200 and a low dielectric loss below 0.06 at room temperature. Furthermore, the ¿r value of this sample shows rather independent with temperature. SEM micrographs show that the sample is dense (¿ 90% of theoretical density) and the grain size of the samples was gradually reduced with increasing x. This CaCu3Ti4-xMnxO12 system is believed to be a promising candidate for capacitor applications.

Dielectric Properties of CaCu3Ti4−xMnxO12 Ceramics

This paper reports the dielectric properties of the Mn doped CaCu3Ti4O12 (CCTO) ceramics synthesized by the conventional solid‐state reaction method. By partial Mn for Ti substitution, the dielectric loss was suppressed significantly while the dielectric constant (er) still remained high. The compound CaCu3Ti3.76Mn0.24O12 exhibits a high er (>1200) and a low dielectric loss (<0.06 at room temperature). Furthermore, the er value of this material is reasonably independent of temperature. SEM micrographs show no impurity in the Mn doped CCTO ceramics, which exhibit dense microstructures without abnormal grains. This CaCu3Ti4−xMnxO12 system appears to be a promising candidate for capacitor applications.

The Acoustic Impedance and other Properties of (1-3) Piezoceramics Polymer Composite

The work is focused on an attempt to develop a route for the fabrication of piezoceamic-polymer composites having (1-3) type connectivity. The process included the extrusion of rods of diameter approximately 200 mm. A commercial piezoelectric, PC-5 was modified by addition of a lithium/bismuth based glass former together with excess PbO to lower the sintering temperature to about 1000 °C. The fast firing sintering was employed. The rods were assembled and impregnated with an epoxy resin to form 1-3 composites containing approximately 50 and 20 vol% piezoceramic. The measurement values showed that, the piezoelectric constant, d33 = 232 pCN-1 and 215 pCN-1, thickness electromechanical coupling coefficient, kt = 0.51 and 0.5 and the mechanical quality factor, Qm = 14 and 5 for the composites containg PZT rods at 50 vol% and 20 vol% respectively. Their acoustic impedances were 5.1 and 3.6 for the 50 vol% and 20 vol% of PZT rods respectively. The results show that with lower volume% of PZT could result in lower acoustic impedance which can be further improved for biomedical imaging and hydrophone applications.

The Fabrication and Dielectric Constant of (1-3) Piezoceramic Polymer Composites

Piezoceramic-polymer composites having (1-3) type connectivity and of a scale size suitable for high frequency >1 MHz transducers was carried out in this study. The piezoceramics (PbZr0.52Ti0.48O3, PZT) were prepared by the conventional mixed oxide route. The starting powders of PbO, ZrO2 and TiO2 were mixed and calcined at 800oC. The calcined powder was mixed with excess PbO and a lithium/bismuth-based glass forming in order to lower the sintering temperature to approximately 1000oC. A method for extruding rods of approximately 400 m diameter was developed. The fast firing process was carried out to sinter the PZT rods. Then the rods were assembled and impregnated with epoxy resin to form 1-3 composites containing approximately 20 and 50 vol% piezoceramics. Both PZT rods and the composites were studied by a scanning electron microscope (SEM). The dielectric properties of the composites were measured. The equivalent capacitance model was employed to determine the dielectric for comparison.

The Effect of GeO2 and In2O3 Doping on the Dielectric Properties of CaCu3Ti4O12 Ceramics Prepared via Vibro-Milling Method

In this work, effects of GeO2 and In2O3 doping on the dielectric properties of CCTO were investigated. Doping levels range from 0.5 to 2.0 mol%. The vibro-milling method was employed for processing. The dopant addition produced a slightly smaller grain size. A reduction in dielectric constant was observed, but it is still high. The 2.0 mol% GeO2 and In2O3 doped samples exhibited high dielectric constant of about 25,000 and 23,000 and low dielectric loss with 0.06 and 0.05 respectively at room temperature and at 10 kHz. The dielectric measurements showed that the modified samples exhibited a strong dielectric independency of temperature and frequency. In addition, the loss tangent reduced after doping. From this results, it can be incurred that GeO2 and In2O3 doping, processed via vibro-mill are the suitable methods to achieve the stability of high ϵr and low loss ceramics.

Ferroelectricity of (1-x)(Bi0.5Na0.5)TiO3 – xBa(Ti0.95Zr0.05)O3 Solid Solution Ceramics

(1-x)(Bi0.5Na0.5TiO3)-xBa(Ti0.95Zr0.05)O3 ceramics were prepared by the mixed oxide technique and their dielectric, piezoelectric and ferroelectric properties determined in detail in the range x = 0.06 to 0.09. At x = 0.07 the maximum relative permittivity of 1338 and piezoelectric constant of 167 pC/N were obtained. It was concluded that 0.93(Bi0.5Na0.5TiO3)-0.07Ba(Ti0.95Zr0.05)O3 is the morphotropic phase boundary region for this system.

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.