Papers by Keyword: Electroceramics

Abstract: Lead Zirconate Titanate (PZT) ceramics are of great technological interest because of their excellent piezoelectric and ferroelectric properties. In this research, an effort will be made to enhance the PZT properties by doping with other elements. The objective of this research is to enhance the dielectric, hence increase the efficiency and performance of piezofan. Properties that piezoelectric fan should have are high mechanical piezoelectric coupling factor, high dielectric constant, easily polarized and high piezoelectric charge constant. Soft and isovalent dopant was a very suitable candidate to fulfill this requirement. The samples will be prepared via high planetary mill and use optimum compaction pressure due to these processes can skip calcinations process, which can reduce a lot of cost. This process also can avoid PbO loss during firing process. The proposed elements are isovalent dopant which is Sr²⁺ and donor dopant which is La³⁺ to subtitude Pb²⁺ at the A-site of PZT. Dopant is beneficial to the enhancement of physical properties of PZT – based ceramics. It also effectively improved the dielectric properties of PZT ceramics due to the effect of average grain size.

Abstract: Results of fabrication and study of Ba_1-xLa_xTi_1-x/4O₃ (BLT) ceramics for x within the range 0.001≤x≤0.004 is reported in the present paper. BLT ceramics has a structure based on ABO₃–type perovskite, and its properties strongly depend on the chemical com_{Subscript text}position. The interrelated semiconductor and ferroelectric properties of La-doped BaTiO₃ ceramics were considered for describing its electrical properties. Dielectric properties were studied in frequency domain by impedance spectroscopy with a Quadtech 1920-type precision LCR meter at room temperature T=RT.

Abstract: A Ni-modified La0.6Sr0.4Fe0.8Co0.2O3 / Ce0.9Gd0.1O2 catalyst was prepared by incipient wetness. The product thus obtained was calcined at 1100°C for 2 h in static air. After thermal activation, Ni was mainly present as highly dispersed La2NiO4 on the surface of perovskite surface. The thermal reduction at 800 °C caused the occurrence of metallic Ni on the surface. Surface area was determined by BET measurement. The catalyst was used as anode in IT-SOFCs fed with methanol. Studies under steam reforming, partial oxidation and autothermal reforming of methanol were carried out at 800°C. A comparison was made between the performance of SOFCs fed with syngas or methanol. The results with methanol are promising both in terms of energy density as well as suitable performance for portable power sources.

Abstract: Many different types of ceramic materials are currently being studied as possible cathodes in Solid Oxide Fuel Cells (SOFC), in an attempt to reduce operating temperatures. Strontium-doped neodymium manganite (Nd1-xSrxMnO3±δ) was used as an intermediate temperature solid oxide fuel cell cathode. X-ray diffraction and electrical conductivity of the Nd1-xSrxMnO3±δ system with a perovskite structure were studied in function of x equal to 0.10, 0.30 and 0.50. An orthorhombic pseudo-perovskite structure was assigned to all powder compositions prepared by standard ceramic technique. Electrical conductivity was described by the small polaron hopping conductivity model, as well as, increases due to regular increments of Sr content for all compositions. Electrical conductivity was measured at 25.2, 26.4 and 37.1Scm-1 for x = 0.10, 0.30 and 0.50, respectively at 800°C.

Abstract: SrTiO3 is one of the most technologically important dielectric ceramics. In this paper, SrTiO3 nanoparticles were synthesized by a simple sol-gel route using NaOH to adjust the pH of the system. Three different strontium-containing starting precursors (Sr(NO3, SrCl2.6H2O and Sr(CH3COO)2.0.5H2O) were employed. Thermogravimetric analysis (TGA) showed complete decomposition of organics at approximately 800°C; this temperature was chosen as a calcination temperature. At 800°C, 6 hours, only the nitrate route with pH = 10 gives single-phase SrTiO3. Other conditions yield various impurities, most likely due to the incompletion of the reaction although they still contain very broad XRD peaks corresponding to SrTiO3, signifying the probable phase formation capability at these conditions. The obtained SrTiO3 powders are in the nanoscale range of 10 to 40 nm with isotropic morphology.

Abstract: A middle permittivity dielectrics with the tunable temperature coefficient of dielectric constant (τε) in the BaO-TiO2-Nb2O5 system, Ba3Ti5Nb6O28, has been synthesized and characterized. The dielectric properties of Ba3Ti5Nb6O28 measured at 1MHz are as follows: dielectric constant (εr) ~38, dielectric loss (tanδ)<0.0002, temperature coefficient of dielectric constant (τε)~-22ppm/°C. The Ba3Ti5Nb6O28 phase satisfies the requirements of NP0 (MLCC) dielectrics, but the sintering temperature of the Ba3Ti5Nb6O28 phase (1250~1300°C) is too high to be co-fired with Ag or Cu electrodes. To lower the sintering temperature, an appropriate amount of ZnO-B2O3 frit (5~7wt.%) was added to the Ba3Ti5Nb6O28 phase and dense ceramics were obtained at the sintering temperature lower than 1000°C. Furthermore, the CaNb2O6 phase with the positive τε of 65ppm/°C was incorporated into the Ba3Ti5Nb6O28 phase to adjust the temperature coefficient of dielectric constant from negative to positive(-22~30ppm/°C). Near zero τε ceramics with high εr (38) and low tanδ (0.0002) were obtained at the composition of Ba3Ti5Nb6O28/ CaNb2O6/ ZB frit=76:17:7 wt.%.