Anocha Munpakdee

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.

Ferroelectric Glass-Ceramics from the PbO-Bi2O3-GeO2 System

he glass ceramics from the PbO-Bi3O2-GeO2 system have been investigated. An excellent transparent glass can be obtained from the stoichiometric (S) composition, Pb3Bi2(GeO4)3, but only by rapid-quenching to give very thin samples. This glass could not therefore be used to make good glass-ceramic samples for measuring the dielectric properties. The A-composition (34.50%PbO :11.49%Bi2O3: 54.01%GeO2) and B-composition (25.90%PbO: 8.63%Bi2O3: 65.47%GeO2) have been prepared to form more stable glasses. These two compositions gave good transparent and thick glass samples. DTA analysis has been used to examine the crystallisation temperatures of all glasses. The controlled heat treatment process has been applied to all crystallisation temperatures and glass-ceramic samples were obtained. It was found that S glass-ceramic contained Pb3Bi2(GeO4)3 and Bi2GeO5 while A glass-ceramic contained only Pb3Bi2(GeO4)3 and was suitable for using in dielectric measurement. B glass-ceramic gave difficulty in identifying the phases. However, it was concluded that the glass-ceramic from this composition had three phases, which are PbGe4O9, PbGeO5 and Bi4(GeO4)3. Since this glass gave no PbO-Bi2O3-GeO2 ternary phase, the dielectric measurement concentrates only on the A glass-ceramic. The frequency dependence of eeee²²²² for the A glass-ceramic sample gave a loss peak at low frequency.

Preparation of Potassium Sodium Niobate in Tellurite Glass System Doped with Er2O3

In the present study, potassium sodium niobate (KNN) doped with Er2O3 in TeO2 glasses were successfully prepared using melting-quenching method. The glass composition of 70KNN-30TeO2 mol% doped with 1 mol% of Er2O3 has been chosen. A batch was subsequently melted at 800°C and 900°C for 30–60 min and heated at the temperature ranging between 300–530°C in order to form the glass ceramics with desired crystal phases. XRD results showed that KNN crystals distributed over the glass-ceramic samples. From SEM observation, it was found that nano-crystals of several phases were precipitated in all glass-ceramic matrices. Dielectric constant increased with increasing heat treatment temperature.

Fabrication of P2O5-CaO-Na2O Glasses Doped with Zinc Oxide for Artificial Bone Applications

The purpose of this work was to study the effect of ZnO on properties of P2O5-CaO-Na2O glass system for bone substituting applications. The glass formula used in this study is 45P2O5 - (30-x)CaO - 25Na2O - xZnO where x = 0, 1 , 3, and 5 mol%. The corresponding glasses were prepared by conventional glass melting technique at 1000 °C for 1 h. Thermal parameters of each glass were studied by differential thermal analysis (DTA). These glasses were investigated in terms of infrared spectra and in vitro bioactivity. DTA results gave the glass transition temperatures in a range 227-280°C and crystallization temperatures in the range 521-529°C. Form FTIR results, the infrared spectra of all glass samples showed vibrations of phosphate network and the transmittance intensity of glass systems decreased with increasing ZnO content. All glass samples were exhibited the growth of apatite cells at the surface after immersed in SBF for 7 days. The optimum composition was found for the glass samples containing 5 mol% ZnO which contained the most apatite layer formation.

Mechanical Properties and Microstructure of Li2O-SiO2-P2O5-Al2O3-K2O-CaO Glass-Ceramics

In this study, the mechanical properties and microstructure of lithium disilicate glass–ceramics in the Li2O-SiO2-Al2O3-K2O-P2O5-ZrO2-CaO glass system were investigated. The glass-ceramics were prepared from the glass melt by casting into mold on hotplate. After that the glass was heat treated at 650-800 °C for 2 h. The heat treatment temperatures were determined from the differential thermal analysis (DTA). The phase formation and microstructure of the glass–ceramics were characterized by X-ray diffraction (XRD) technique and the scanning electron microscopy (SEM). Moreover, the mechanical properties was investigated by Vickers hardness testing. The results indicated that the samples confirmed the occurrence of Li2SiO3, Li2Si2O5, Li3PO4, and LiAlSi2O6 phases in the prepared glass ceramics. The optimum heat treatment temperature results in the physical properties with a high Vickers hardness values in the range of 5.4-5.8 GPa.

Effects of BST on Optical and Dielectric Properties of Na2O-B2O3-SiO2 Glasses

In this research, the effects of Ba0.7Sr0.3TiO3 (BST) on optical and dielectric properties of Na2O-B2O3-SiO2 glasses were investigated. From the study, the optically transparent glass from BST system was successfully prepared by using melt-quench method. The composition of BST used in this study are ranging between 20-60 wt.% BST. It was found that the addition of BST enhanced conductivity, but in turn reduced the percentage of transmittance in the glasses. The dielectric constant (ɛr) of the BST/Na2O-B2O3-SiO2 glasses improved with increasing the content of BST, which in turn plays an important role in controlling the properties of the BST/Na2O-B2O3-SiO2 glasses.

Fabrication of SrFe12O19-P2O5-CaO-Na2O Bioactive Glass-Ceramics at Various Sintering Temperatures

The effects of sintering temperatures on the physical, and bioactivity of SrFe12O19 (SF)-P2O5-CaO-Na2O bioglass ceramics were investigated. XRD results confirmed the existence of the strontium ferrite and calcium phosphate phases. SEM images showed that grain size, and hardness were related to density and liquid phase present in the samples. A maximum coercivity value of 3138 Oe was obtained for the bioglass ceramic sintered at 600°C. The remanence (Mr) and saturation magnetization (Ms) of the bioglass ceramic sintered at 500°C possess the maximum value of 6.35 and 10.64 emu/g, respectively. Moreover, the apatite was formed on the surface layers of the bioglass ceramics confirming their biocompatibility.

Effects of thermal treatment on piezoelectric and dielectric properties of zirconium modified barium titanate ceramics

In this work, zirconium doped barium titanate ceramics were prepared via a solid state technique. After sintering at 1,450°C for 2h, the ceramics were annealed at 1,200°C for 4-16 h. Effects of the thermal treatment on the electrical properties of the ceramics were investigated. An improvement in strain level and piezoelectric coefficient were observed especially for the sample annealed for 8 h. Bipolar strain level and piezoelectric coefficients (d*33) of the 8 h sample were 0.26% and 326 pm/V, respectively. The dielectric constants of the annealed samples were also significantly improved. The piezoelectric and dielectric properties could be correlated with changes in densification and microstructure.

Characteristics of 45S5 Bioglass-Ceramics Using Natural Raw Materials

The aim of this work was to analyze the effect of using rice husk ash (RHA) and bovine bone as raw materials of glass-ceramics based on the SiO2-Na2O-CaO-P2O5 system on their physical, mechanical properties and bioactivity. All of the investigated compositions were prepared by melting the glass mixtures at 1300°C for 3 h. The resulting glass samples were heated at different temperatures ranging from 600 to 1000°C with fixed dwell-time for 2 h for crystallization. Phase identification of the prepared glass ceramics was carried out by X-Ray diffraction (XRD) and scanning electron microscope (SEM) techniques. In addition, in vitro test was carried out in stimulated body fluid (SBF). Differential thermal analysis (DTA) showed that the glass transition occurred at 505°C and crystallization at 700°C. The main crystalline phase form in most glass ceramics is a sodium calcium silicate. The optimum heat treatment temperature, at which the maximum mechanical value (620 HV) could be obtained, is around 1000°C. After incubation in SBF for 7 days, all of the samples show good bioactivity in vitro, as evident by the formation of bone like apatite phase.