Papers by Keyword: Dielectric

Abstract: The annealing temperature of 250nm PVDF-TrFE (70:30 mol%) spin coated thin films were optimized. The annealing temperature were varies starting from solvent evaporation (T_s), Curies transition (T_c), up to melting temperature (T_m). The result shows that the dielectric constant increases with the increasing of annealing temperature. Supported with the XRD observation indicating there were an improvement in crystallinity consistently with the increasing of the annealing temperature. Morphological properties of the annealed PVDF-TrFE thin films were observed by utilizing Field Emission Scanning Electron Microscope (FESEM) at 100k magnification. It can be found that, the annealing temperature promotes the development of elongated crystallite structure which known as ferroelectric crystal. However, the presence of nanoscale cracks on the thin film annealed at 160°C (AN160, over T_m) suggesting high possibility to posed defects while in device applications.

Abstract: The conducting polymer electrolyte films composed of polyacrylonitrile (PAN) as the host polymer, LiCF₃SO₃ and NaCF₃SO₃ as inorganic salts and ethylene carbonate (EC) as plasticizer were prepared by the solution cast technique. The conductivities of the films were characterized by impedance spectroscopy. On addition of more than 14 wt% of salt, the NaCF₃SO₃-containing PAN films exhibited higher ionic conductivity than the LiCF₃SO₃-containing PAN films. The values of the dielectric constant, ε_r and dielectric loss, ε_i increase as frequency decreases at room temperature. The temperature dependence of the conductivity obeys Arrhenius relation in the temperature range of 303 K to 353 K.

Abstract: Bi_3.25Gd_0.75Ti_2.97V_0.03O₁₂ (BGTV) ceramics were prepared by solid state reaction. These samples had polycrystalline Bi-layered perovskite structure without preferred orientation, and consisted of well developed plate-like grains with random orientation. The remanent polarization and the coercive field of the BGTV were 24μC/cm² and 65kV/cm at an electric field of 100kV/cm, respectively. These ferroelectric properties of BGTV are superior to V-doped Bi₄Ti₃O₁₂ (~20μC/cm² and 80kV/cm) and (Sr, Ta)-doped Bi₄Ti₃O₁₂ (~12μC/cm² and 71kV/cm) ceramics. In addition, the dense ceramics of BGTV could be obtained by sintering at temperatures 100─200°C lower than those of the SrBi₂Ta₂O₉ system.

Abstract: Bi_2.9Pr_0.9Ti_2.97V_0.03O₁₂ (BPTV) ceramics were prepared by solid state reaction. These samples had polycrystalline Bi-layered perovskite structure without preferred orientation, and consisted of well developed plate-like grains with random orientation. BPTV caused a large shift of the Curie temperature ( TC ) of Bi₄Ti₃O₁₂ (BIT) from 675°C to 385°C. The remanent polarization and the coercive field of the BLTV were 31μC/cm² and 60kV/cm at an electric field of 100kV/cm, respectively. Furthermore, the dielectric permittivity and dissipation factor were 300 and 3.3×10-3 at 1MHz, at 1V and at room temperature, respectively. These ferroelectric properties of BPTV are superior to V-doped Bi₄Ti₃O₁₂ (~20μC/cm² and 80kV/cm) and (Sr, Ta)-doped Bi₄Ti₃O₁₂ (~12μC/cm² and 71kV/cm) ceramics. In addition, the dense ceramics of BPTV could be obtained by sintering at temperatures 100─200°C lower than those of the SrBi₂Ta₂O₉ system.

Abstract: Bi_3.25Er_0.75Ti₃O₁₂(BET) and Bi_3.25Er_0.75Ti_2.97V_0.03O₁₂(BETV) thin films with random orientation were fabricated on Pt/Ti/SiO₂/Si substrates by rf magnetron sputtering technique. These samples had polycrystalline Bi-layered perovskite structure without preferred orientation, and consisted of well developed rod-like grains with random orientation. The experimental results indicated that Er doping into Bi₄Ti₃O₁₂ (BIT) also result in a remarkable improvement in ferroelectric property. The remanent polarization (Pr) and coercive field (Ec) of the BET film were 17 μC/cm² and 80 kV/cm, respectively. Furthermore, V substitution improves the Er value of the BETV films up to 28 μC/cm², which is much larger than that of the BET film.

Abstract: The ferroelectricity of Bi_3.2Er_0.8Ti₃O₁₂ (BET), and Bi_3.2Er_0.8Ti_2.97V_0.03O₁₂ (BETV) ceramics prepared at 1100°C by a conventional ceramic technique was investigated. These ceramics possess random-oriented polycrystalline structure. The remanent polarization (Pr) and coercive field (Ec) of the BET ceramics are 18 µC/cm² and 64kV/cm, respectively. Furthermore, V substitution improves the Pr value of the BETV ceramics up to 30 μC/cm², which is much larger than that of the BET ceramics. Therefore, co-sustitution of Er and V in Bi₄Ti₃O₁₂ (BIT) ceramic is effective for the improvement of its ferroelectricity.

Abstract: The ferroelectricity of Bi_3.25Nd_0.75Ti₃O₁₂ (BNT), and Bi_3.25Nd_0.75Ti_2.97V_0.03O₁₂ (BNTV) ceramics prepared at 1100°C by a conventional ceramic technique was investigated. These ceramics possess random-oriented polycrystalline structure. The remanent polarization (Pr) and coercive field (Ec) of the BNT ceramics are 16 µC/cm² and 65kV/cm, respectively. Furthermore, V substitution improves the Pr value of the BNTV ceramics up to 23 μC/cm², which is much larger than that of the BNT ceramics. Therefore, co-sustitution of Nd and V in Bi₄Ti₃O₁₂ ceramic is effective for the improvement of its ferroelectricity.

Abstract: The Ferroelectric properties and Microstructures of Bi_3.3Tb_0.6Ti₃O₁₂ (BTT) and Bi_3.3Tb_0.6Ti_2.97V_0.03O₁₂ (BTTV) ceramics prepared at 1100°C by a conventional ceramic technique were investigated. These ceramics possess random-oriented polycrystalline structure. The remanent polarization (Pr) and coercive field (Ec) of the BTT ceramics are 23µC/cm2 and 80kV/cm, respectively. Furthermore, V substitution improves the Pr value of the BTTV ceramics up to 35μC/cm², which is larger than that of the BTT ceramics. Therefore, co-sustitution of Tb and V in Bi₄Ti₃O₁₂ (BIT) ceramic is effective for the improvement of its ferroelectricity.

Abstract: Electrical Discharge Machining (EDM) in Malaysia is widely used in mould making industries. Parts for automotive, defence and telecommunication industries are also other examples of the products produced. The process is based on removing material from a part by a series of repeated electrical discharges between a tool called electrode and the work piece with the presence of dielectric. The dielectric serves as transportation of removed particles, remains electrically non-conducting until the breakdown voltage is reached, reconditions the dielectric strength, increases the energy density in plasma channel and cools the electrode. This paper presents the machining of ASSAB 718HH work pieces with copper tool using EDM die sinking method. Three commercial EDM dielectrics; Kerosene, Novis and Amoil were tested and comparison between material removal rate (MRR), tool wear ratio (TWR) and surface finish (SF) are given. Through Pugh Method, result shows that ASSAB 718HH is best machined with Novis.

Abstract: Piezoelectric materials have wide applications in today’s advanced technologies. However, most commercially used piezoelectric material PZT (PbZr1-xTixO3) is now strictly restricted worldwide due to hazardous nature of Pb. Research for the development of new lead free materials with properties comparable to that of PZT is in progress in recent years. In the present work, an effort has been made to synthesize low amount of rare earth gadolinium modified (Bi1-xGdx)0.5Na0.5TiO3 (BGNT) with compositions (x) = 0, 0.02, 0.03 and 0.04 by a novel Semi–Wet Technique. The structural, microstructure, phase transition and dielectric properties have been investigated. The XRD patterns have shown single phase formation for all the samples with a rhombohedral symmetry at RT. Gd3+ doping has shown a significant effect on the grain growth. The dielectric measurement has been carried out over the temperature range from RT to 400 oC at 1, 10 and 100 kHz frequency. It has been observed from the εr vs T plots that two phase transitions (i) ferroelectric to anti-ferroelectric and (ii) anti ferroelectric to paraelectric occur in all the samples. The composition with x = 0.02 has shown significantly high value of dielectric constant (εr ~ 1567) and low value of dielectric loss (Tan δ ~ 0.043) at room temperature.