ISSN:
1573-4803
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract Polycrystalline zirconia fibres, doped with 2–8 mol% of oxides of trivalent lanthanum, praseodymium, neodymium, samarium, gadolinium, and dysprosium (in decreasing cation size), were prepared by spinning of acetate-derived sols and baking the gel fibres thus obtained at 900–1300 °C for 1 h. The larger sized dopants lanthanum, praseodymium and neodymium (Group A) gave rise to tetragonal zirconia, with or without cubic zirconia, at 900 °C which converted partly or fully to monoclinic zirconia, in certain cases accompanied by a cubic zirconate phase at higher temperatures. The smaller sized dopants samarium, gadolinium and dysprosium (Group B) generated only tetragonal or cubic, or both polymorphs of zirconia, depending on the cation type, concentration and temperature. This “stabilization” of higher symmetry polymorphs with Group B dopants was associated with relatively large crystallite size (especially when calcined at 1300 °C). The maximum tensile strength values of usable fibres calcined at 1300 °C were found to decrease with increasing size in dopant dysprosium 〉 gadolinium 〉 samarium 〉 neodymium, praseodymium, lanthanum=0). Although all the dopant cations were larger in size than Zr4+ (in the same oxygen coordination), the relative closeness in size of Group B cations with Zr4+ was considered to be the reason behind the obtained differences in properties.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00354448
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