Chatchai Kruea-In

Relaxor behaviour of K0.5Bi0.5TiO3-BiScO3 ceramics

Dielectric properties of (1 − x)K0.5Bi0.5TiO3 − xBiScO3 ceramics have been studied for compositions x ≤ 0.5. Single-phase solid solutions occurred for compositions x < 0.25. A frequency-dependent dielectric relaxation was observed, consistent with relaxor behaviour. This gave rise to a relatively stable dielectric permittivity at high temperatures, for example, ɛr = 2880% ± 3%, between temperatures of 500 and 700 K (1 kHz) for composition x = 0.15. This consistency in relative permittivity occurs at higher temperatures than for other lead-free dielectrics. Parameters from Vogel-Fulcher analysis are compared to other relaxors.

Properties of 0.94Bi0.5Na0.5TiO3–0.06BiAlO3 Ceramics Prepared by Two Steps Sintering Technique

In this research, 0.94Bi0.5Na0.5TiO3–0.06BiAlO3 ceramics were prepared by the conventional solid-state reaction and the two steps sintering. X-ray diffraction analysis revealed that both samples showed a pure perovskite phase. Scanning electron microscopy study revealed that both ceramics had similar microstructure. The two steps sintering affects the phase transition temperature of the ceramics. Dielectric and ferroelectric properties of the two steps sintering samples are better than that of the conventional sample. The results were related to the densification and the degree of crystallinity of the samples.

Effects of NiO nanoparticles on electrical and magnetoelectric properties of BNT based ceramics

The properties of 0.94BNT-0.06BT/xNiO lead-free nanocomposites were investigated. The NiO additive influenced dielectric properties as well as the phase transition behavior of the samples. Dielectric properties under applied magnetic fields were also measured. After addition of the additive, the loss tangent could be controlled by an applied magnetic field. Furthermore, the P-E hysteresis loop changed from a normal hysteresis loop for the unmodified sample to a constricted loop for the x = 0.5 and 1.0 vol. % samples, and then became a lossy capacitor hysteresis loop for the x = 2.0 vol. % sample. These results suggest that NiO nanoparticles have a strong influence on the properties of the composites.

Dielectric Characteristics and Tunability of Barium Zirconium Titanate Ceramics Prepared by Two-Step Sintering Method

Barium zirconium titanate ceramics with a composition of BaZr0.07Ti0.93O3 were synthesized using a modified two step sintering process and the dielectric and mechanical properties of the ceramics were investigated. The modified sintering helped to improve the sinterability of the samples resulting in a high ceramic density. Improvements in the dielectric constant, dielectric tunability and hardness values were also observed. The enhancements in dielectric and mechanical properties were directly related to the improvement in densification of the samples.

Fabrication of Sodium Potassium Niobate Ceramics by Two Step Sintering Assisted Molten Salts Synthesis

Potassium sodium niobate (KNN) powders were synthesized by a molten salt synthesis. The pure phase KNN was achieved for a calcination temperature of 500 °C which is lower than the conventional technique by 400°C. The KNN ceramics were then fabricated by a two steps sintering technique. Effects of dwell time at T 2 on the properties of the ceramics were investigated. Although there was unchanged in microstructure, the dielectric results indicate that a longer dwell time produced a higher value of peak dielectric constant. However, the 8 h sample exhibited the densest ceramic and showed a better ferroelectric performance.

Electrical behaviors of (1-x)BZT07-xBNWT lead free solid solution binary system

Solid solutions of the (1−x)Ba(Zr0.07Ti0.93)O3-xBa((Ni0.5W0.5)0.1Ti0.9)O3 system with 0.05 ≤ x ≤ 0.2, were fabricated via a solid-state reaction technique. All samples exhibited a pure phase perovskite structure. The x = 0.05 samples exhibited very high dielectric constants (>60,000) for temperatures over 400°C, while the x = 2.0 samples had a higher degree of dielectric constant stability over a wide temperature range. The ceramics also showed a dielectric relaxor behavior. The frequency dependence of the loss tangent peak was observed to follow an Arrhenius law where the activation energies increased with increasing Ba((Ni0.5W0.5)0.1Ti0.9)O3 content. The result suggests that the addition of Ba((Ni0.5W0.5)0.1Ti0.9)O3 has strong effects on the properties this ceramic system.

Effects of vibro-milling on relaxor ferroelectric behavior and phase transition of lead-free Ba(Zr0.25Ti0.75)O3 ceramics

Lead-free Ba(Zr0.25Ti0.75)O3 ceramics were synthesized from powders prepared by a conventional mixed oxide and vibro-milling method to investigate the phase transition, dielectric response, and ferroelectric properties of the prepared samples. Compared to a conventional sample, the samples prepared by the vibro-milling method showed a higher dielectric constant at the ferroelectric-to-paraelectric transition temperature. The vibro-milling method also produced a stronger frequency dependence on the dielectric constant. To confirm the dielectric properties and phase transition behavior, ferroelectric hysteresis measurements were carried out in the temperature range −40°C to 80°C. The microstructural properties of the samples were investigated and the results were then correlated with the characteristics of the milled and calcined powder as well as the grains of the ceramics.

Effects of NiO Nanoparticles on Physical and Mechanical Properties of BNKT Lead-Free Ceramics

In this research, The effects of NiO nanoparticles on the physical and mechanical properties of Bi0.5(Na0.81,K0.19)0.5TiO3 (BNKT) were investigated. The ceramics were synthesized by solid state reaction technique. The powder of BNKT was calcined at 850 °C for 4 h. The ceramics of BNKT/x NiO vol.% ( i.e. x= 0.0, 1.0, 2.0 and 3.0) were sintered at 1000-1150 °C for 2 h for optimize condition. Densification, phase formation, microstructure and micro hardness of samples were characterized via Archimedes method, X-ray diffraction techniques (XRD), scanning electron microscope (SEM) and Vickers micro hardness tester. The X-ray diffraction analysis of the ceramics suggests that all samples exhibited a perovskite structure. Densification of samples tended to increase with increasing amount of NiO content with minimun at 1.0 vol.% NiO additive. The NiO additive influenced densification as well as the mechanical properties of the samples. The results of this research suggest that NiO nanoparticles have influence on physical and mechanical properties of BNKT ceramics.

Influence of Processing Temperature on Properties of Sr(Fe0.5Nb0.5)O3 High Dielectric Ceramics

Influence of processing parameters, calcination and sintering temperatures, on the properties of Sr(Fe0.5Nb0.5)O3 samples were investigated The Sr(Fe0.5Nb0.5)O3 ceramics were fabricated by a solid-state reaction method. X-ray diffraction analysis revealed that pure perovskite phase of SFN powders was observed for the calcination temperatures ≥1000°C. However, all SFN ceramics showed the pure perovskite phase. Average grain size increased with increasing sintering temperature, where the hardness value was related with grain size. The dielectric properties examination indicated that increase of the sintering temperature is effective in improving dielectric constant of the SFN ceramics.

Effect of vibro-milling on dielectric properties of barium zirconium titanate ceramics

Barium zirconium titanate powders were prepared by conventional ball milling and vibro-milling methods. Barium zirconium titanate ceramics were fabricated from the obtained powders. Properties of the ceramics were investigated. The vibro-milling ceramics showed a better dielectric constant and relative tunability. It is proposed that the better densification and degree of crystallinity for the vibro-milling ceramics are responsible for better ceramics properties.