The crystallized mullite composite has been synthesized via sol-gel technique in the presence of transition metal ions such as iron and copper. The electrical resistivity and activation energy of the composites have b...The crystallized mullite composite has been synthesized via sol-gel technique in the presence of transition metal ions such as iron and copper. The electrical resistivity and activation energy of the composites have been measured and their variation with concentration of the metal ion has been investigated. The resistivity of doped mullite decreases rapidly in the shorter temperature range and sharply in the higher temperature range. The decreasing resistivity is due to the 3d orbital electrons and the concentration of metal ions present. X-ray analysis confirms the presence of metal ions in mullite, which entered in the octahedral site. The Fe2+ and Cu2+ ions will substitute Al3+ ion in the octahedral site of mullite structure and most probably will be responsible for reducing the resistivity as well as the activation energy. Transition metal ion doped mullite-based ceramic can be considered as promising material as a substrate in the electronic industry, because of its reasonable atom density, its low activation characteristics, low thermal expansion coefficient and high mechanical strength. The present material we have developed has an activation energy of resistivity/band gap energy, Eg, 1.11 eV at 0.04 M concentration for Cu2+ ion.展开更多
Monophasic mullite （3Al2O3？2SiO2） samples doped with 0.002 M, 0.02 M, 0.1 M, 0.15 M and 0.2 M of cobalt were prepared by a sol-gel process. Prepared gels were then dried, grinded, pressed into pellets and sintered ...Monophasic mullite （3Al2O3？2SiO2） samples doped with 0.002 M, 0.02 M, 0.1 M, 0.15 M and 0.2 M of cobalt were prepared by a sol-gel process. Prepared gels were then dried, grinded, pressed into pellets and sintered at 1 000 °C and 1 300 °C for 4 h. Phase formation and densification behavior has been investigated as a function of the cobalt content and sintering temperature. Mullite densification behavior was analyzed .The density of the sintered ceramics was measured using Archimedes method. CoO and Co related compounds were detected by the analysis for G3, G4 and G5 doping levels. The mullite X-ray diffraction suggests predominant incorporation of Co in the glassy phase, whose quantity increased with the doping level.展开更多
文摘The crystallized mullite composite has been synthesized via sol-gel technique in the presence of transition metal ions such as iron and copper. The electrical resistivity and activation energy of the composites have been measured and their variation with concentration of the metal ion has been investigated. The resistivity of doped mullite decreases rapidly in the shorter temperature range and sharply in the higher temperature range. The decreasing resistivity is due to the 3d orbital electrons and the concentration of metal ions present. X-ray analysis confirms the presence of metal ions in mullite, which entered in the octahedral site. The Fe2+ and Cu2+ ions will substitute Al3+ ion in the octahedral site of mullite structure and most probably will be responsible for reducing the resistivity as well as the activation energy. Transition metal ion doped mullite-based ceramic can be considered as promising material as a substrate in the electronic industry, because of its reasonable atom density, its low activation characteristics, low thermal expansion coefficient and high mechanical strength. The present material we have developed has an activation energy of resistivity/band gap energy, Eg, 1.11 eV at 0.04 M concentration for Cu2+ ion.
文摘Monophasic mullite （3Al2O3？2SiO2） samples doped with 0.002 M, 0.02 M, 0.1 M, 0.15 M and 0.2 M of cobalt were prepared by a sol-gel process. Prepared gels were then dried, grinded, pressed into pellets and sintered at 1 000 °C and 1 300 °C for 4 h. Phase formation and densification behavior has been investigated as a function of the cobalt content and sintering temperature. Mullite densification behavior was analyzed .The density of the sintered ceramics was measured using Archimedes method. CoO and Co related compounds were detected by the analysis for G3, G4 and G5 doping levels. The mullite X-ray diffraction suggests predominant incorporation of Co in the glassy phase, whose quantity increased with the doping level.
