Sintering of ZrO2 ‐ CeO2 Spherical Powders Prepared by a Water Extraction Variant of the Sol‐Gel Process

Abstract

Spherical powders (with diameters <I00 ~m) of zirconia-ceria hydroxide gels (stabilized with nitrates or chlorides) were fabricated by a water extraction variant of the sol-gel process. The resulting powders were calcined at 400, 600, and 800~ in order to obtain crystalline forms, subsequently pressed at various pressures, and then sintered for 8 h at 1700~ The sintered pellets had relatively high geometric density (in some cases >95% of the theoretical density) and showed both tetragonal and/or cubic x-ray phases. The bulk density values of these ceria-doped zirconia sintered pellets are much higher than those obtained for the CaO-or Y2Oa-doped zirconia samples prepared by the same process.Fully and partially stabilized ZrO2 solid solutions are one of the most extensively studied solid oxide electrolyte systems due to the many practical applications of these materials. In order to stabilize the high temperature, high conductive tetragonal, and/or cubic phases, CaO, Y20~, or MgO have been extensively utilized as dopants. Recently, the addition of CeO2, as a stabilizer of ZrO2, has demonstrated the capability for producing a fairly large-grained (20-40 p~m) pure tetragonal solid solution with high flexure strength and fracture toughness.

New Directions in Inorganic and Metal-Organic Coordination Chemistry in Supercritical Fluids

“…Coprecipitation techniques , can also be employed to access such materials, but they require strict control of several variables (e.g., pH, temperature, and stirring rate) and there is no guarantee that homogeneous mixtures will be obtained. By comparison, sol−gel processes − and high energy mechanical ball-alloying methods can produce relatively homogeneous mixtures. Nevertheless, sol−gel materials still require some postannealing to obtain crystalline products, while ball-milling involves prolonged mixing times.…”

Continuous hydrothermal synthesis of inorganic materials in a near-critical water flow reactor; the one-step synthesis of nano-particulate Ce1 − xZrxO2 (x = 0–1) solid solutions

“…6 Furthermore, supported noble metal/ceria±zirconia catalysts have been also reported as having higher OSCs and can be reduced at signi®cantly lower temperatures than CeO 2 ± ZrO 2 materials alone. 6 Conventionally, solid solutions of Ce 12x Zr x O 2 can be prepared using methods such as high temperature solid state synthesis, 11,12 high energy ball milling, 9 sol±gel, 8,11 microemulsion methods 13 and co-precipitation with ageing of solutions. 14 However, many of these techniques are time consuming (multi-step syntheses or ageing), energy intensive and environmentally unfriendly.…”

Preparation of ceria-zirconia solid solution with enhanced oxygen storage capacity and redox performance

“…Several methods have been used to synthesize ceriazirconia solid solutions, such as coprecipitation [7], solgels [8], microwave-hydrothermal [9], high-energy ball milling [10], etc. However, these methods tolerate high costs or low productivity for practical application.…”