Oleshko Vladimir P, Howe James M, Shukla Satyajit, Seal Sudipta
Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904-4745, USA.
J Nanosci Nanotechnol. 2004 Sep;4(7):867-75. doi: 10.1166/jnn.2004.110.
Submicron and nano-sized nanocrystalline pure zirconia (ZrO2) powders having metastable tetragonal and tetragonal-plus-monoclinic crystal structures, respectively, were synthesized using the sol-gel technique. The as-precipitated and the calcinated ZrO2 powders were analyzed for their morphology, nanocrystallite size and structures, aggregation tendency, local electronic properties, and elemental compositions by conventional and high-resolution transmission electron microscopy and field-emission analytical electron microscopy, including energy-dispersive X-ray and electron energy-loss spectroscopies. The results from this study indicate that a combination of nanocrystallite size, strain-induced grain-growth confinement, and the simultaneous presence of the monoclinic phase can lead to stabilization of the metastable tetragonal-phase in undoped ZrO2. As a result, the tetragonal phase is stabilized within ZrO2 nanocrystallites up to 100 nm in size, which is 16 times larger than the previously reported critical size of 6 nm.
分别使用溶胶-凝胶技术合成了具有亚稳四方晶相和四方相加单斜晶相晶体结构的亚微米级和纳米级纳米晶纯氧化锆（ZrO₂）粉末。通过传统和高分辨率透射电子显微镜以及场发射分析电子显微镜，包括能量色散X射线和电子能量损失谱，对沉淀态和煅烧后的ZrO₂粉末的形态、纳米微晶尺寸和结构、聚集趋势、局部电子性质以及元素组成进行了分析。该研究结果表明，纳米微晶尺寸、应变诱导的晶粒生长限制以及单斜相的同时存在相结合，可导致未掺杂ZrO₂中亚稳四方相的稳定。结果，四方相在尺寸达100 nm的ZrO₂纳米微晶中得以稳定，这比先前报道的6 nm临界尺寸大16倍。
