Rangson Muanghlua

Non-isothermal kinetics of the thermal decomposition of sodium oxalate Na2C2O4

The thermal transformation of Na2C2O4 was studied in N2 atmosphere using thermo gravimetric (TG) analysis and differential thermal analysis (DTA). Na2C2O4 and its decomposed product were characterized using a scanning electron microscope (SEM) and the X-ray diffraction technique (XRD). The non-isothermal kinetic of the decomposition was studied by the mean of Ozawa and Kissinger–Akahira–Sunose (KAS) methods. The activation energies (Eα) of Na2C2O4 decomposition were found to be consistent. Decreasing Eα at increased decomposition temperature indicated the multi-step nature of the process. The possible conversion function estimated through the Liqing–Donghua method was ‘cylindrical symmetry (R2 or F1/2)’ of the phase boundary mechanism. Thermodynamic functions (ΔH*, ΔG* and ΔS*), calculated by the Activated complex theory and kinetic parameters, indicated that the decomposition step is a high energy pathway and revealed a very hard mechanism.

Extraction of mobility degradation, effective channel length and total series resistance of NMOS at elevated temperature

This article describes the extraction of total series resistance, effective channel length and low field effective channel mobility degradation parameter at temperature in the range of 25°C–125°C of NMOS device. The relation of I<inf>DS</inf> and V<inf>GS</inf> in a linear region was used with a different of channel length. The procedure is based on the measurement of the transconductance characteristics of MOSFET in the linear region. The transconductance characteristics is determine for the several devices of difference drawn channel length. The results shows that, the effective channel length is increased in a range of 5×10⁻¹⁰ m/°C. The low field mobility degradation parameter is decreased by the factor of 0.733. The total series resistance is increased in the range of 1.4 Ω-µm/°C. The errors between the predicted model and measured of I<inf>DS</inf>&V<inf>GS</inf> in linear region is approximately 3 %

High Strain Response of the (1-x)(0.94Bi0.5Na0.5TiO3-0.06BaTiO3)-xBaSnO3 Lead Free Piezoelectric Ceramics System

The system of lead free piezoelectric ceramics, (1-x)(0.94Bi0.5Na0.5TiO3-0.06BaTiO3)-xBaSnO3 [abbreviated as BNT-BT-xBSn] with the compositions, x = 0.00, 0.02, 0.04, 0.06, 0.08 and 0.10 was synthesized via the conventional solid state reaction method. All the products from X-ray diffraction patterns showed diffraction peaks as a phase perovskite structure, with no secondary phases. Due to the composition-dependence of the ferroelectric, bipolar and unipolar strain properties were investigated in order to achieve a good new lead free piezoelectric ceramics system. It was noticeable that a large strain of around 0.4%, with a normalized strain value (d33*) of 669 pm/V at the x = 0.02composition, by applying an electric field of 60 kV/cm at room temperature. The results of this study showed that a new BNT-BT-xBSn ceramics system is a very promising candidate for creating a significantly large strain response, which is sufficiently effective for actuator material applications.

Effect of Pb(Y1/2Nb1/2)O3 Additions on Thermal and Electrical Properties of PbZrO3 Ceramics

The solid solution of a (1–x)PbZrO3 – xPb(Y1/2Nb1/2)O3 (PZ – PYN) system, with x = 0.00 – 0.08, was synthesized by the wolframite precursor method. The effects of PYN content on crystal structure, and electrical and thermal properties of PbZrO3 ceramic were investigated. The crystal structure of sintered ceramics was characterized by X-ray diffraction. The pure perovskite phase was obtained for all compositions. The transition temperatures of the AFE to PE phase become lower with PYN increase. The dielectric properties of PZ were improved by the addition of PYN.

Preparation and Properties of Lead Free Bismuth Sodium Titanate−Bismuth Zinc Titanate Ceramics

Lead-free piezoelectric ceramics based on (1–x)Bi 1/2 Na 1/2 TiO 3 – x Bi(Zn 1/2 Ti 1/2 )O 3 (x = 0.0, 0.02, 0.04, 0.06, 0.08, 0.10, 0.20, 0.30, 0.40, and 0.5) were obtained via solid-state processing techniques. The influence of BZT addition on BNT characteristics, sintering, microstructure and properties was investigated. A single perovskite phase with rhombohedral symmetry was obtained for Bi(Zn 1/2 Ti 1/2 )O 3 substitutions of up to 10 mole%. A small amount of BZT was effective for improving both sintering behavior and dielectric properties of BNT ceramics. Optimized dielectric properties were obtained for samples with a maximum density of ρ = 98.3% for the composition, x = 0.1.

Synthesis and Morphology Evolution of Lead-Free Piezoelectric K1/2Na1/2NbO3 Powder at Low Temperature

A synthetic route for modified solid state reaction has been developed for the synthesis of the perovskite phase of potassium sodium niobate, K1/2Na1/2NbO3 (KNN). Potassium oxalate monohydrate (K2C2O4.H2O) and sodium oxalate (Na2C2O4) were employed as a source of potassium and sodium, respectively. The formation of the K1/2Na1/2NbO3 phase was investigated as a function of calcination conditions by TG-DTA and XRD techniques. Morphology and particle size were determined via an SEM technique. It was found that the minor phases of Na2CO3 and K2CO3 tend to form together with K1/2Na1/2NbO3, depending on calcination conditions. The perovskite phase was successfully synthesized at a low temperature of 400°C. As calcination temperatures increased from 600° to 850°C, the KNN solid solution became more homogeneous, XRD peaks became narrower, and a pattern similar to that expected for orthorhombic K1/2Na1/2NbO3 was achieved after 600°C, as indicated by the separate peaks of 0 2 2 and 2 0 0.

Dielectric, Ferroelectric and Piezoelectric Properties of the Lead Free 0.9BaTiO3-(0.1-x)Bi0.5Na0.5TiO3-xBi(Mg0.5Ti0.5)O3 Solid Solution

Solid solution of 0.9BaTiO3-(0.1-x)Bi0.5Na0.5TiO3-xBi(Mg0.5Ti0.5)O3 (BT-BNT-xBMT) system, where x = 0.00, 0.02, 0.04, 0.06, 0.08, 0.10, was synthesized by the solid state reaction. Dense BT-BNT-xBMT ceramics were obtained by sintering at 1,150–1,250˚C for 4 h. The effect of BMT on crystal structure and electrical property of BT-BNT ceramics was investigated as a function of composition, x, using X-ray diffraction, dielectric spectroscopy, hysteresis and strain measurements. The crystal structure of solid solution BT-BNT-xBMT, where x = 0.00-0.10, successively transforms from tetragonal to pseudocubic symmetry, with increased BMT concentration. Temperature dependence of dielectric constant (ϵr) and dielectric loss (tanδ) for BT-BNT-xBMT at various frequencies showed that phase transition of ceramics changed from ferroelectric to relaxor-like behavior as BMT content increased. Furthermore, remanent polarization (Pr), coercive field (Ec) and the normalized strain (d33*) of BT-BNT-xBMT ceramics tend to decrease with increasing BMT concentration.

Fine Grain BaTiO3-Co0.5Ni0.5Fe2O4 Ceramics Prepared by the Two-Stage Sintering Technique

This work investigated the improvement of density and controllable grain size of multiferroic ceramics by using the system of (0.8)BaTiO3-(0.2)Co0.5Ni0.5Fe2O4 nanocomposites via the two-stage sintering technique. The sintering process was divided into two steps. Firstly, samples were fired at the optimized temperature of T1 to activate grain boundary migration in order to obtain an initial high density. Secondly, the samples were cooled immediately to the temperature of T2 and soaked at various times to enable dense ceramics without grain growth. All of the samples were characterized by an X-ray diffractometer, and the results confirmed that all samples were composite ceramics. Scanning electron microscopy showed the grain size of all the samples and proved that the two-stage sintering technique achieved fine grain ceramics when compared with traditional sintering. Electrical properties of all the samples were investigated using an LCR meter at room temperature to 200°C with various frequencies, and magnetic properties were characterized by a vibrating sample magnetometer.

Fabrication and Properties of BaTiO3-CoFe2O4 Nanocomposites

In this work, BaTiO3-xCoFe2O4, where x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5, nanocomposites were prepared by conventional mixing method and followed by normal sintering in air. The effect of processing condition on phase formation, microstructure, magnetic and electrical properties of the BaTiO3-CoFe2O4 nanocomposites was investigated. The phase development and microstructural evolution of this system have been determined via X-ray diffractometer and scanning electron microscope. From the results, it concludes that phase formation, microstructure, electrical and magnetic properties of the BaTiO3-xCoFe2O4 nanocomposites strongly depend on chemical composition.

The Influence of BMN Addition on the Phase Formation, Microstructure and Dielectric Property of BaTiO3 Ceramic

Solid solutions of the (1−x)BT-xBMN system were prepared successfully by the solid state reaction method followed by normal sintering in air. The phase formation, microstructure and dielectric property of BT-BMN ceramics were investigated as a function of compositions. XRD results showed a single perovskite phase for all compositions. Cubic-tetragonal transformation was found after adding BMN into the system. SEM micrographs revealed two very different grain sizes in the ceramics, with compositions of x = 0.02, 0.03, 0.04 and 0.05. Fine grains indicated a cubic structure, whereas large ones indicated a tetragonal structure. Regarding the dielectric property, Curie temperature decreased with increasing BMN content, whereas the ϵr value increased until the BMN content reached 3 mol% before dropping to a lower value.