Synchrotron X-ray diffraction study of the tetragonal–cubic phase boundary of nanocrystalline ZrO₂–CeO₂synthesized by a gel-combustion process

Abstract

The crystal structures of a number of nanocrystalline ZrO 2 -CeO 2 solid solutions, synthesized by a pH-controlled nitrate-glycine gel-combustion process, were studied. By using a synchrotron X-ray diffractometer, small peaks of the tetragonal phase, which correspond to forbidden reflections in the case of a perfect cubic fluorite structure, were clearly detected. By monitoring the most intense of these reflections, 112, as a function of the CeO 2 content, the tetragonal-cubic phase boundary was found to be at 85 (5) mol% CeO 2 . For a CeO 2 content up to 68 mol%, a tetragonal phase with c/a > 1 (known as the t 0 form) was detected, whereas, between 68 and 85 mol% CeO 2 , the existence of a tetragonal phase with c/a = 1 and oxygen anions displaced from their ideal positions in the cubic phase (the t 00 form) was verified. Finally, solid solutions with higher CeO 2 contents exhibit the cubic fluorite-type phase.

Humidity Related Low Temperature Conductivity Hysteresis of Ce1–xZrxO2 (0 ≤ x ≤ 1) Ceramics. Structural Disorder Relationship

“…These anodes were prepared as porous metal-ceramic composites, using optimized Ni charges and high surface Ce/Zr supports prepared at relative low temperatures, T ≤ 1,273 K. However, the crystal structure of low temperature prepared samples could differ considerably from that of high temperature phases prepared in this work, where Ce and Zr dilution is favored at high temperatures in intermediate compositions, improving the OSC behavior. The segregation of tetragonal Zr-rich and cubic Ce-rich phases, produced at low temperatures [31,32], could severely affect the reforming performances of electrodes used in SOFC's devices.…”

Local structures surrounding Zr in nanostructurally stabilized cubic zirconia: Structural origin of phase stability

“…However, if the tetragonal phase exists in the sample, the ͑112͒ peak of tetragonal ZrO 2 at around 43°, as well as splitting of the ͑400͒ line of the fluoritelike ZrO 2 structure into ͑004͒ and ͑400͒ lines with more than one degree of separation, should be observed in the XRD data. 12 As we can see from Fig. 2, none of these important evidences for tetragonal zirconia were observed in samples studied by EXAFS here.…”

Thermodynamic Control of Product Formation During the Reaction Between CH4 and Pt Promoted Ceria-zirconia Solid Solutions

“…In Fig. 1 the pseudo-cubic lattice parameter, defined for the tetragonal phases as [29]. The unit cell volume variation obeys the Vegard's law which indicates incorporation of ZrO 2 into the CeO 2 phase without major additional interactions.…”

“…The distinction between these phases, especially between the t and t 0 , and between t 00 and cubic is quite subtle and can hardly be settled by laboratory scale powder X-ray diffraction. By using synchrotron radiation powder XRD, Lamas et al studied the crystal structure of the CeO 2 -ZrO 2 solid solutions and distinguished between tetragonal and cubic phase [29]. In Fig.…”