Piyalak Ngernchuklin

Preparation and Properties of PSZTM Ceramics with Different Methods

The PSZTM ceramics from Pb0.94Sr0.06(Zr0.52Ti0.48)O3 doped with 0.1 mol% Mn were prepared by a solid state reaction and. Two different methods were used to calculate the amount of Mn-dopant into PSZT powder. One was calculated rely on B-site precursor represented by B method. The other was computed based on the amount of calcined PSZT called C method. This study was to investigate the effect of the two different calculating formulations of Mn doped PSZT ceramics by B and C methods on phase formation, microstructure, physical and electrical properties. The results were observed that phase identification showed the formation of perovskite structure in both cases. Besides, the mechanical quality factor (Qm) of the PSZTM ceramics derived from B method was two times higher than those from C method. Nevertheless, the dielectric constant (K), piezoelectric coefficient (d33) and planar coupling coefficient (kp) of the PSZTM ceramics from B method were slightly lower than those of derived from C method. This could be drawn the conclusion that PSZTM with 0.1 mol% Mn prepared by B method can be used as hard-type piezoelectric material.

Comparison of actuator performance in lead-based and lead-free piezoelectric cymbals

Class V flextensional actuator named “cymbal” is composed of a ceramic disk that is sandwiched between two truncated conical metal endcaps. It has received considerable attention for sensor and actuator applications due to their high displacement and moderate generative force. It is well known that the strain/displacement of the piezoelectric ceramic correlated to the piezoelectric coefficient and external electric field applied (S = dE). According to the piezoelectric coefficient (d33) of KNN-LT-LS lead-free piezoelectric ceramic was comparable to PZT-8. Therefore, the purpose of this study was to investigate the effect of different ceramic driving elements (hard PZT and KNN-LT-LS ceramics) in the flextensional cymbal actuator on the strain amplification as well as the characteristic in strain-electric field loop response. The results showed that displacement of KNN-LT-LS cymbal (11.9±0.28 μm) were two times higher than that of PZT-8 cymbal (5.65±0.07 μm) at 10 kV/cm. Moreover, bi-polar S-E loop characteristic was larger in KNN-LT-LS cymbal compared to PZT-8 cymbal. This was due to easily domain reorientation in KNN-LT-LS ceramic observed by P-E loop. Under 10 kV/cm, Pr and Ec of KNN-LT-LS ceramic were 4.9 μC/cm2 and 3.9 kV/cm whereas Pr and Ec of PZT-8 ceramic were 0.22 μC/cm2 and 1.5 kV/cm, respectively.

Preparation of Near-Infrared (NIR) Reflective Pigment by Solid State Reaction between Fe2O3 and Al2O3

Reflective pigment was prepared by using Fe2O3 and Al2O3 as starting materials. Fe2O3 and Al2O3 powders were mixed at 0.8:2, 1:2 and 1.2:2 mole ratio using ball milling. The mixed powders were dried and calcined at temperature of 1500°C, 1600°C and 1700°C for various soaking time at 2, 8 and 20 h. Phase data were analyzed by x-ray diffractometry. It was found that (Al1-x, Fex)2O3 presented as a new phase in calcined powders at temperature of 1500°C to 1700°C for 2 h. The other new phase such as FeAl2O4 was detected in calcined powders at temperature of 1700°C for 8 and 20 h. From the experimental results indicated that complete reaction was occurred when higher calcination temperature and longer soaking time were used, resulting in spinel structure (FeAl2O4) generated. Then, the synthesized powders were mixed with exterior paint by mass ratio of 0:100, 10:90, 20:80, 30:70 and 40:60, respectively. The mixed paints were sprayed on metal sheets. Then the coated metal sheets were exposed under 200 watts lamb and measured the temperature difference between the exposed side and opposite side. The result showed that at the ratio of 30:70 exhibited the highest temperature difference of 14°C approximately. From the result, we concluded that spinel structure (FeAl2O4) is a candidate for near-infrared (NIR) reflective pigment of exterior paint.

Upgrading of Waste Gypsum for Building Materials

In this research, waste gypsum (CaSO4·2H2O), a by-product material from industrial factory, was upgraded and then used as raw material for building materials. The by-product gypsum possessed a high acidic value of 3-point pH scale and moisture content of 40 %. The two properties had an impact on setting reaction and hardening of gypsum. Therefore, the studies of gypsum phase transformation to calcium sulfate hemihydrate (CaSO4·0.5H2O) were focused on washing process and amount of calcium carbonate (CaCO3) added at 0, 1, 3 and 5 % wt. After washing, waste gypsum and washed water were reduced from high acidic value to neutralization (pH = 7) as a result of CaCO3. Next, the neutralized gypsum was heated to the optimal temperature at 160 °C for 2 hours and transformed to hemihydrate gypsum phase observed by XRD. Finally, the relationship of amount of CaCO3-mechanical property such as bending strength will be investigated.

Effect of Milling Time on the Properties of BYF Doped PZT Energy Harvesting Ceramics by High-Energy Ball Milling

Recently, Lead Zirconate Titanate (PZT) has been attracted for energy harvesting (EH) devices because of their excellent piezoelectric properties at the morphotropic phase boundary (MPB). The EH devices require high energy density related to high figure of merit (FOM: g33 x d33). As a result, the improvement of piezoelectric voltage coefficient (g33) and piezoelectric charge coefficient (d33) to better energy density property obtained should be searching for. Therefore, PZT-BYF system was chosen for piezoelectric energy harvester by focusing to study on the composition of 0.99PZT-0.01BYF (0.99Pb(Zr0.53Ti0.47)O3-0.01Bi(Y0.7Fe0.3)O3). In this study, PZT and BYF systems were calcined separately and then 0.99PZT-0.01BYF powders were prepared by solid state method and mixed via high-energy ball milling in various milling time (2, 4, 10 and 16 hrs). The effect of milling time on the physical and electrical properties, figure of merit and microstructure were investigated.

Comparison of Milling Techniques to Figure of Merit of 0.98PZT-0.02BYF Piezoelectric Ceramic Energy Harvester

Nowadays, the concept of harvesting energy from the environment, for example, thermal, wind, sun, vibration and human activities is much of interest. PZT is one of the materials which show an ability to harness vibration energy and then change to electrical energy. Therefore, the PZT (Pb(Zr0.53Ti0.47)O3) doped with 0.02 mol% BYF (Bi(Y0.7Fe0.3)O3) piezoelectric ceramics has been studied to improve the figure of merit (d33*g33). The PZT and BYF powder systems were prepared by solid state reaction with calcination temperature of 800 and 850 °C for 2 h, respectively. XRD results showed that both powders exhibited pure perovskite phase for PZT and single phase of BYF without pyrochlore phase. Then, the two calcined powders (PZT and BYF) were mixed according to the composition of 0.02 mol% BYF doped PZT by two different milling techniques called conventional ball-milling (CBM) and high energy ball-milling (HBM) for 10 h. The result showed that average particle size obtain from HBM was 1 µm which was smaller than from CBM shown up to a few microns in bimodal mode. The PZT-BYF-HBM ceramics showed higher physical and electrical properties but lower K value. Thus promoting to higher g33 which was equal to 36.89 * 10-3(Vm/N) and FOM was 11,632*10-15(m2/N), while PZT-BYF-CBM had g33 of 26.86* 10-3(Vm/N) and FOM at 8,016*10-15(m2/N), respectively.

Electromechanical Displacement of Soft/Hard PZT Bi-Layer Composite Actuator

PZTs can be classified into two types, i.e., soft and hard PZTs, which are categorized by the piezoelectric and ferroelectric properties such as coercive field, piezoelectric strain, mechanical quality factor etc. It is known that the combination effect of the soft/hard PZT composites can generate large strain/actuation compared to monolithic PZT ceramics. In this study, soft and hard PZT powders were co-pressed into bi-layer disks with various ratios between soft and hard PZT powders, ranging from 0:100~100:0 vol. % (with 10 % increments) and then they were co-sintered. Due to the difference in the planar shrinkage of the two layers and thermal expansion coefficient mismatch, dome-shaped bi-layer composites with various dome heights were obtained. It was shown that the constrained layer either soft PZT or hard PZT affected various properties including the dome geometry, the strain-E-field response, and the displacement hysteresis loop. The electromechanical properties and actuation performance of such bi-layer composite actuators have been investigated and compared to the soft and hard PZT single layer counterparts.

Effect of MnCO3 Doping on Microstructure and Electrical Properties of PSZT Ceramics

The effect of manganese doping on microstructure, piezoelectric and electromechanical properties of Pb0.94Sr0.06(Zr0.52Ti0.48)O3 (PSZT) ceramics has studied. The PSZT ceramics doped MnCO3 concentration in the region of 0-1.0 mol% were prepared by a solid-state reaction and conventional sintering process. Phase identification showed the formation of single phase perovskite structure in all compositions. Microstructure and fracture behavior were observed by scanning electron microscopy (SEM). The fracture behavior demonstrated the change of fracture type from trangranular to mix of trans-and inter-granular type with increasing the amount of MnCO3. Dielectric constant (K), d33 and kp were increased when higher amount of MnCO3 was doped. In addition, the mechanical quality factor (Qm) was highest at 0.1 mol% MnCO3 doping in PSZT ceramics.

The Effect of Metallic Plate on the Displacement in Bilayer Piezoelectric/Electrostrictive Dome Unimorph

A dome piezoelectric-electrostrictive monolithic bilayer composite (PE-MBLC) actuator is attached to a thin metallic plate by insulating epoxy resin to form a flextensional actuator. Such flextensional actuator is called bilayer piezoelectric/electrostrictive dome unimorph (BIPEDU). Under the application of an electric field, the force generated from radial contraction of PE-MBLC was transferred through the bonding area to deform the metallic plate, generating more displacement in BIPEDU actuator. In this study, a PE-MBLC with the P:E volume ratio of 8:2 was used as the active driving element and a metallic plate served as a flextensional structure. Different type of metallic plates showed different in the flexibility which will effect to strain amplification in BIPEDU. Therefore, the investigation of various metallic plates including stainless steel, brass, and aluminum with their thicknesses of 76 μm on the displacement of BIPEDU has studied. To examine the displacement, all PE-MBLCs and BIPEDUs were subjected to an E-field of 10 kV/cm. The results showed that displacement of all BIPEDUs with stainless steel, brass, and aluminum yielded higher displacement compared to PE-MBLCs. In addition, the experimental results of displacement in BIPEDUs with three different types of metallic plates indicated that the BIPEDU fabricated by using 76 μm thickness stainless steel yielded the highest displacement of ≈65 μm while BIPEDUs with brass and aluminum showed 45 and 32 μm, respectively.