The present work reports the results of a reinvestigation of the ␥ liquidus and solidus temperatures of the Ni-Al system and the ␥ /Ni 5 Zr eutectic reaction temperatures in the Ni-Al-Zr system. In the Ni-Al binary system, it is found that the stability of the Ni-rich ␥ solid solution phase is enhanced by small additions of Al with the melting temperature of the ␥ phase and that the melting temperature reaches a congruent maximum at a few at.% Al. The temperature of the eutectic reaction L → ␥ ؉ Ni 5 Zr in the Ni-Zr binary edge is confirmed to be 1196 ؇C by differential thermal analysis (DTA), rather higher than the value reported previously. The reaction temperature increases with Al addition to reach or exceed 1206 ؇C, forming a "saddle point," then decreasing to reach 1187 ؇C or below by flowing into a ternary invariant reaction. These findings can be explained by ␥ /liquid equilibrium in the Ni-Al binary system. addition on the temperature of the eutectic reaction L → ␥ ϩ Seiji Miura, Hiroto Unno, Tetsuro Yamazaki, Satoshi Takizawa, and between melting points can be measured directly.
Microstructures of TiO(2)-doped alpha-Al(2)O(3) ceramics used as electrostatic chucks (ESC) were investigated by transmission electron microscopy including energy-dispersive spectrometry (EDS) and electron energy loss spectroscopy (EELS) analyses in connection with their electrical properties. The lattice parameters of sintered Al(2)O(3) grains are almost independent of TiO(2) content as well as the sintering temperature, indicating immiscibility of the additive with Al(2)O(3). Scanning transmission electron microscopy (STEM)-EDS revealed that the grain boundaries of alpha-Al(2)O(3) are slightly enriched with Ti. It was shown in EELS that the segregated Ti is in a partially reduced state. The Ti-enriched grain boundaries, therefore, play a role as a conductive network, which is responsible for considerable improvement of electronic conductivity with TiO(2) doping. STEM-EDS and electron diffraction analyses confirmed that micrometre-sized TiO(2) particles are dispersed in the alpha-Al(2)O(3) when sintering is operated at 1300 degrees C or lower, while the particles transform into Al(2)TiO(5) at higher temperature. EELS revealed that the TiO(2) grains are partially reduced into non-stoichiometric TiO(2-y), while Al(2)TiO(5) grains are in the fully oxidized state. The TiO(2-y)-dispersed alpha-Al(2)O(3) shows no dielectric relaxation and quite smooth dissipation of the electrostatic condensed charges. In contrast, alpha-Al(2)O(3) with Al(2)TiO(5) grains possesses pronounced dielectric relaxation, and the electrostatic dissipation takes such a longer time as 30 s. The former is preferable to application to ESC in terms of quick response.
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