Synthesis of Nanosize Yttria-Stabilized Zirconia by a Molecular Decomposition Process

Effect of thermal treatment on the crystal structure and morphology of zirconia nanopowders produced by three different routes

“…Because of its phase transformation from tetragonal to monoclinic around the temperatures range from 1100 to 2370 • C, it is a challenging study with potentially practical applications to prepare stabilized tetragonal ZrO 2 powders at low temperatures. Stabilization of t-ZrO 2 phase is usually achieved by adding oxides of yttrium, magnesium, calcium, thorium, titanium, cerium and ytterbium (Piticescu et al, 2001;Jiang et al, 2001;Lascalea et al, 2004;Teterycz et al, 2003;Panda et al, 2003;Zhang et al, 2004;Ai and Kang, 2004;Bhattacharjee et al, 1991). According to the change in thermal treatment, c-ZrO 2 phase is stable at all temperature up to the melting point at 2680 • C. m-ZrO 2 phase is stable below 1170 • C and inverted to t-ZrO 2 phase by increasing temperature over 1200 • C. t-ZrO 2 phase is stable between 1170 and 2370 • C by adding stabilized oxides (Stefanc et al, 1999).…”

Synthesis of Nanosize Tin Dioxide by a Novel Liquid‐Phase Process

“…The latter mechanism involves molecular decomposition in which the fugitive constituent (here Na 2 O) is leached away from the solid precursor (Na 2 SnO 3 ) to form soluble products (either NaOH in the case of H 2 O or NaNO 3 in the case of HNO 3 ) and leaving behind an insoluble oxide (nanosize SnO 2 ). The formation of nanosize powders by molecular decomposition has been previously demonstrated in which nanosize ZrO 2 was formed by reacting Na 2 ZrO 3 with H 2 O 16 . The exact assignment ratio of these parallel reactions will depend on specific reaction conditions, such as the ratio of the precursor solid to the liquid, presence or absence of HNO 3 , reaction temperature and time, etc.…”

“…Assuming particles to be spherical for simplicity, the particle diameter ( D ) may be estimated from the following relation 16 : where ρ is the density of SnO 2 and S is the specific surface area. With ρ=6.95 g/cm 3 for SnO 2 , and the measured BET surface area of S =220 m 2 /g, the particle diameter is estimated to be ∼3.9 nm.…”

Powder synthesis, processing and characterization of lanthanum silicates for SOFC application

“…The patterns perfectly match JCPDF card 49-0443, which is the standard pattern for undoped lanthanum silicate (La 9.33 Si 6 O 26 ), indicating that the powder does not have any undesired secondary phases. The crystallite size is 32 nm, as calculated according to the Scherrer formula [11].…”