Rare-earth doped zirconia fibres by sol-gel processing

• Published in: Journal of materials science 1996-12, Vol.31 (23), p.6263-6267
• Main Authors: NASKAR, M. K, GANGULI, D
• Format: Article
• Language: English
• Subjects: Applied sciences; Building materials. Ceramics. Glasses; Ceramic and carbon fibers; Ceramic industries; Chemical industry and chemicals; Exact sciences and technology; Technical ceramics
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/BF00354448

Polycrystalline zirconia fibers, 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 fibers thus obtained at 900-1300 deg 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 deg 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 deg C). The maximum tensile strength values of usable fibers calcined at 1300 deg 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 Zr exp 4+ (in the same oxygen coordination), the relative closeness in size of Group B cations with Zr exp 4+ was considered to be the reason behind the obtained differences in properties.