| Summary: | 博士 === 國立中山大學 === 材料科學研究所 === 94 === Nanocrystalline α-Zr condensates deposited by ion beam sputtering on the NaCl (100) surfaces and then annealed at 100 ℃ to 750 ℃ in air. The phases present were identified by transmission electron microscopy to be nanometer-size α-Zr+ZrO、α-Zr+ZrO+c-ZrO2、c-ZrO2、c-+t-ZrO2、t-ZrO2、and t-+m-ZrO2 phase assemblages with increasing annealing temperature. The zirconia showed strong {100} preferred orientation due to parallel epitaxy with NaCl (100) when annealed between 150 ℃ and 500 ℃ in air. The c- and t-zirconia condensates also showed (111)-specific coalescence among themselves. The c- and/or t-ZrO2 formation can be accounted for by the small grain size, the presence of low-valence Zr cation and the lateral constraint of the neighboring grains. (Part 1)
Nanocrystalline α-Zr condensates were deposited on the NaCl (100) plane at 25 to 450 ℃ by radio frequency ion beam sputtering from a pure 99.9％ Zr disk. The nano condensates were identified by transmission electron microscopy to be quasiamorphous, α-Zr, α-Zr+ZrO and α-Zr+ZrO+c-ZrO2 phase assemblages with increasing substrate temperature. At 400 ℃ and under 1-20 sccm oxygen, c- and t-ZrO2 nanocondensates were assembled on NaCl (100) as monolayer nanocrystalline material and showed strong preferred orientation. The c- and/or t-ZrO2 were retained by small grain size, low-valence Zr cation and 2-D matrix constraint of the film. (Part 2)
Nanosized c- and t-ZrO2 were formed as monolayer nanocrystalline film on NaCl (100) plane by radio frequency ion beam sputtering. The microstructure and the epitaxy relationship with the NaCl (100) plane were studied by a high resolution transmission electron microscope. The epitaxy orientation was found to be [001]Z//[001]N, [100]Z//[1 0]N (group A), and [011]Z//[001]N, [100]Z//[100]N (group B) between zirconia (Z) and NaCl (N). Group B has two variants and is the dominant type. The possible causes for the epitaxy relationship are discussed. Crystallites within the same group can merge by rotation and coalesce into a single crystal, whereas crystallites in different groups can form high-angle grain boundaries. (Part 3)
Special interfaces were formed for the c- and/or t-ZrO2 (Z) nano-crystals when deposited on the NaCl (N) (100) cleavage plane by ion beam sputtering to follow the epitaxy relationships of [001]Z//[001]N, (100)Z//(1 0)N (group A); and [011]Z//[001]N, (100)Z//(100)N (group B1) or (100)Z//(010)N (group B2). The nanoparticles in group A and B were impinged and coalesced to form {220}A/{200}B and {200}A/{111}B interfaces; with anchored dislocation whereas those in group B1 and B2 form {220}B1/{200}B2 interface. The {220}A/{200}B interface is found to be of especially low energy due to good match O2– lattice sites, and smoothly joints {200} and {220} planes across the interfaces without mismatch strain and dislocations. The special interfaces may shed light on the epitaxial mechanism of nanocrystalline materials in general. (Part 4)
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