Parkpoom Jarupoom

Lead-free ternary perovskite compounds with large electromechanical strains

Lead-free compounds based on perovskite solid solutions in the ternary system (Bi1/2Na1/2)TiO3–(Bi1/2K1/2)TiO3–Bi(X1/2Ti1/2)O3, where X = Ni and Mg have been shown to exhibit large electromechanical strains. While the perovskite end members Bi(Mg1/2Ti1/2)O3 and Bi(Ni1/2Ti1/2)O3 display limited stability in their pure state, both compounds were found to have solid solubilities of at least 50 mol. % with (Bi1/2Na1/2)TiO3 and (Bi1/2K1/2)TiO3. Most importantly, under relatively large applied fields, these materials exhibited large hysteretic electromechanical strains characterized by a parabolic shape. With effective piezoelectric coefficients (d33*) greater than 500 pm/V, these systems have excellent potential as a Pb-free piezoelectric materials.

Effects of NiO nanoparticles on the magnetic properties and diffuse phase transition of BZT/NiO composites

A new composite system, Ba(Zr0.07Ti0.93)O3 (BZT93) ceramic/NiO nanoparticles, was fabricated to investigate the effect of NiO nanoparticles on the properties of these composites. M-H hysteresis loops showed an improvement in the magnetic behavior for higher NiO content samples plus modified ferroelectric properties. However, the 1 vol.% samples showed the optimum ferroelectric and ferromagnetic properties. Examination of the dielectric spectra showed that the NiO additive promoted a diffuse phase transition, and the two phase transition temperatures, as observed for BZT93, merged into a single phase transition temperature for the composite samples.

Improvement in piezoelectric strain of annealed Ba(Zr0.07Ti0.93)O3 based ceramics

In the present work, effects of annealing time on strain behavior, densification, and microstructure of 2 wt. % B2O3 doped Ba(Zr0.07Ti0.93)O3 ceramics were investigated. The ceramics were initially sintered at 1150 to 1275 °C for 2 h. After sintering, the densest ceramics (1250 °C ceramics) were selected for annealing at 1000 °C for 4-16 h. An increase in strain level and piezoelectric coefficient was observed after some annealing. High bipolar strain level of 0 .48% and high piezoelectric coefficients (d*33) of 603 pm/V were obtained for the 8 h samples. Longer annealing times (>8 h) resulted in reduction of the strain level and piezoelectric value. The change in piezoelectric properties was correlated with the densification and microstructure of the studied samples.

Structures and Properties of Lead-Free NKN Piezoelectric Ceramics

In this work, the preparation of sodium potassium niobate (Na0.5K0.5)NbO3 (NKN) ceramics were carried out by the conventional method. The effect of calcination temperatures, dwell time and heating rate on phase formation was investigated. Earlier work reported that to achieve the density of NKN ceramic over 95% of its theoretical density is rather difficult. In this work, firing conditions and heating and cooling rates were carefully varied to fabricate the NKN ceramics. X-ray diffraction (XRD) techniques were used to investigate the phase evolution of the calcined powders and sintered bodies. Microstructures of sintered pellets were studied by the scanning electron microscopic (SEM) techniques. Dielectric and ferroelectric properties were also investigated and reported.

Effect of Particle Size on the Dielectric Properties of Sodium Potassium Niobate -Portland Cement Composites

In this research, the effect of sodium potassium niobate, (Na0.5K0.5)NbO3 (NKN) particle size on the dielectric properties of 0-3 non lead based piezoelectric cement based composites were investigated. NKN of various particle sizes (75, 225 and 450 μm) were used at 50% by volume to produce the composites. Dielectric properties at various frequencies (0.1–20 kHz) were investigated. The results showed that the dielectric values of NKN-PC composites increased with increasing NKN particle size where ϵ r at 1 kHz are 158.60 and 191.21 for composites with 75 μm and 450 μm NKN particle size respectively. The dielectric loss (tanδ) was found to reduce with increasing NKN particle size and the tan δ value was lowest at 0.39 for composite with 450 μm NKN particle size.

Effects of annealing time on ferroelectric and piezoelectric properties of B2O3 doped Ba(Zr0.07Ti0.93)O 3 ceramics

The method of thermal annealing was applied to B2O3 doped BaZr0.07Ti 0.93O3 ceramics. The modified ceramics were prepared via a solid state reaction method. The samples were sintered at 1250°C for 2 h, and then followed by the thermal annealing at 1000°C for 4–16 h to improve their electrical properties. The ferroelectric properties were slightly decreased. However, an enhancement of piezoelectric properties was observed after annealing, especially for 8 h annealing. The results were discussion in term of composition variation after annealing.

Improvement of Ferroelectric and Dielectric Properties of Annealed Pyrochlore Free PZT Based Ceramics

The method of thermal annealing was applied to 0.05PZN-0.15PNN-0.8PZT ceramics to improve its electrical properties. The ceramics were prepared via a columbite method: sintered at 1250°C for 2 h, followed by the thermal annealing at 900°C for 8–24 h. Improvements in many electrical properties such as dielectric and ferroelectric properties were observed. Annealing for 8 h was found to be the optimum annealing condition for the ceramics. The results were discussed in term of densification and composition variation after annealing.

High Dielectric and Piezoelectric Properties Observed in Annealed Pb0.88Sr0.12Zr0.54Ti0.44Sb0.02O3 Ceramics

The dielectric, ferroelectric, and piezoelectric properties of ceramics from the Pb0.88Sr0.12 Zr0.54Ti0.44Sb0.02O3 system were investigated as a function of annealing time after being prepared via the solid-state method. Following the annealing process, a shift in the ferroelectric to paraelectric transition temperature (Tm) was observed. In addition, a high relative permittivity >24300 at Tm was recorded for the 64 h annealed sample which was 52% higher than that of the as-sintered samples. The increased annealing time produced an enhancement in the ferroelectric properties and a high piezoelectric coefficient (d33) of 670 pC/N was also observed for the 64 h annealed sample.

Synthesis and Properties of 0.8PZT-0.10PZN-0.10PNN Ceramics

The 0.8PZT-0.10PZN-0.10PNN powders were synthesized via a columbite method. Pure perovskite phase was obtained at the calcinations temperature ≥ 900°C. Ceramics with the same composition were fabricated at various sintering temperatures. The densest ceramic with pure phase perovskite was obtained at the sintering temperature of 1250oC for 4 h. The ceramics showed two phase transition at ∼265°C and ∼291°C which correspond to orthorhombic to tetragonal and tetragonal to cubic phase transition, respectively. The obtained ceramics also showed a very high dielectric constant >40000. The ferroelectric properties were investigated and discussed.

Phase transition and dielectric properties of B2O3 doped BZT ceramics

In the present work, effects of B2O3 (a flux addition) on phase transition behaviour and dielectric properties of BZT ceramics were investigated. The ceramics were prepared by a solid state sintering method. Properties of the ceramics were characterized by X‐ray diffraction, electron microscopy, and dielectric measurement. The dielectric measurement showed that the ferroelectric phase transition of the ceramics became broader and phase transition temperatures increased as the amount of B2O3 increased. The results also suggested that boron ions were introduced into the lattice and altered the phase transition characteristics of the ceramics.In the present work, effects of B2O3 (a flux addition) on phase transition behaviour and dielectric properties of BZT ceramics were investigated. The ceramics were prepared by a solid state sintering method. Properties of the ceramics were characterized by X‐ray diffraction, electron microscopy, and dielectric measurement. The dielectric measurement showed that the ferroelectric phase transition of the ceramics became broader and phase transition temperatures increased as the amount of B2O3 increased. The results also suggested that boron ions were introduced into the lattice and altered the phase transition characteristics of the ceramics.