Authors: Ning Zhang Wang, Sha Sha, Yu Tian Ma
Abstract: MnCO3, CuO, NiO and Fe2O3 doped SrTiO3 multifunction ceramics were fabricated firstly. The microstructure and electrical properties were investigated. The results show that MnCO3 doped ceramic and CuO doped ceramic possess relative higher resistivity (ρ),nonlinear coefficient (α), varistor voltage (V1mA) and relative lower dielectric constant (ε),dielectric loss (tgδ) in contrast with NiO doped ceramic and Fe2O3 doped ceramic with the same contents under the same sintering conditions. The electrical properties among the ceramics doped are different due to the different behaviors of Mn,Cu,Ni and Fe acceptor dopants during the sintering course.
1603
Authors: Cheng Hua Zhang, Bin Jiang, Ke Zhang, Lei Jiao, Ren Hong Yu, Dong Xu
Abstract: Sc2O3-doped zinc oxide varistor ceramics were prepared by a solid reaction route. The microstructure and the electrical properties was analyzed by scanning electron microscope and X-ray diffraction. Sintering time influences on the microstructure and the electrical properties of Sc2O3-doped zinc oxide varistor ceramics are studied. The results show that the electrical properties of Sc2O3-doped zinc oxide varistor ceramics sintered at 1000 and sintered for 1 h was better: the voltage gradient was 653 V/mm; the leakage current was 0.18 μA and the nonlinear coefficient was 57.1.
126
Authors: Tan Guan Kui, Mohd Fariz Ab Rahman, Zainal Arifin Ahmad, Julie Juliewatty Mohamed
Abstract: The Ni1-xCuxO was prepared from raw materials of NiO and CuO via solid state reaction. This study was focuses on undoped and CuO doped NiO properties. CuO was used as dopant with five different concentrations. The powders were mix for 24 hours and followed by calcinations at 900°C for 2 hours. The calcined powders were compacted to a 5 mm diameter pellet form, by applying 200 MPa pressure. Then, the pellets were sintered at temperature 1200°C for 12 hours. After that, the samples were analyzed by using XRay diffraction (XRD) in order to identify the phase formation, scanning electron microscopy (SEM) for the microstructure and surface topography observation, density measurement by Archimedes principle and impedance analyzer in order to measure the dielectric properties. XRD results show that all sintered pellets produce a single phase of Ni1-xCuxO. In addition, increase of Cu dopant concentration causes the lattice parameter getting larger. Apart from that, SEM shows that more addition of Cu dopant increase the grain size. The density is also improved, due to formation of bigger grain size lead to an increasing in density. Impedance analyzer results show the dielectric behaviour of the samples was improved with increasing of CuO content. The 0.10 mol% CuO obtained optimum dielectric properties with lowest dielectric loss measured at 1 GHz (0.008).
3
Authors: Mariah Oliveira Juliani, Carolyne Davi Oliveria, Rosa Maria Rocha
Abstract: Zirconium diboride (ZrB2) is a covalent compound that leads the category of ultra high temperature ceramics materials owing to its unique properties. In this work, the effect of addition of beta-silicon carbide (β-SiC) in pressureless sintering of ZrB2 was investigated. Four compositions were prepared with 0, 10, 20 e 30 vol% of SiC. ZrB2 powder and mixtures were prepared in by planetary milling with SiC spheres at 4 h. Two sintering temperatures were used, one at 2050 oC/1h and other at 2150 °C/1h. The addition of SiC has promoted an increasing in densification with the increasing of SiC content. The total densification of sample sintered at 2050 oC was 90% of theoretical density for sample with 30 vol% of SiC, while the maximum densification for temperature of 2150 oC was 91,0 %TD.
250
