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Rare-Earth Zirconate Ln2Zr2O7 (Ln: La, Nd, Gd, and Dy) Powders, Xerogels, and Aerogels: Preparation, Structure, and Properties
journal contribution
posted on 2019-10-15, 15:45 authored by Jorge Torres-Rodriguez, Vanessa Gutierrez-Cano, Melita Menelaou, Jaroslav Kaštyl, Jaroslav Cihlář, Serhii Tkachenko, Jesús A. González, József Kalmár, István Fábián, István Lázár, Ladislav Čelko, Jozef KaiserThe physicochemical
properties of rare-earth zirconates can be
tuned by the rational modification of their structures and phase compositions.
In the present work, La3+-, Nd3+-, Gd3+-, and Dy3+-zirconate nanostructured materials were prepared
by different synthetic protocols, leading to powders, xerogels, and,
for the first time, monolithic aerogels. Powders were synthesized
by the co-precipitation method, while xerogels and aerogels were synthesized
by the sol–gel technique, followed by ambient and supercritical
drying, respectively. Their microstructures, thermogravimetric profiles,
textural properties, and crystallographic structures are reported.
The co-precipitation method led to dense powders (SBET < 1 m2 g–1), while
the sol–gel technique resulted in large surface area xerogels
(SBET = 144 m2 g–1) and aerogels (SBET = 168 m2 g–1). In addition, the incorporation of lanthanide
ions into the zirconia lattice altered the crystal structures of the
powders, xerogels, and aerogels. Single-phase pyrochlores were obtained
for La2Zr2O7 and Nd2Zr2O7 powders and xerogels, while defect fluorite
structures formed in the case of Gd2Zr2O7 and Dy2Zr2O7. All aerogels
contain a mixture of cubic and tetragonal ZrO2 phases.
Thus, a direct effect is shown between the drying conditions and the
resulting crystalline phases of the nanostructured rare-earth zirconates.