Synthesis and characterization of Gd₂Zr₂O₇ defect-fluorite oxide nanoparticles via a homogeneous precipitation-solvothermal method

Abstract

Defect-fluorite structured Gd2Zr2O7 nanoparticles were successfully synthesized via a homogeneous precipitation-solvothermal method using urea as a precipitant.

Uranium-Incorporated Pyrochlore La2(UxMgxZr1–2x)2O7 Nuclear Waste Form: Structure and Phase Stability

“…In the past decades, there have been many researches on the property, radiation resistance, and stability of pyrochlores as waste host materials. − It has been clear that actinides can be effectively incorporated into the A 2 B 2 O 7 matrix on both A and B sites. − However, the resulting compound can crystallize in the ordered pyrochlore structure (space group Fd 3̅ m ) or the defect fluorite structure (space group Fm 3̅ m ) depending on the cation radius ratio of VIII A 3+ / VI B 4+ . When the radius ratio is between 1.46 and 1.78, the preferred phase at ambient conditions is the ordered pyrochlore, ,− where there are two distinct crystallographic sites (16c and 16d), as shown in Figure . The trivalent cation, such as La 3+ , Y 3+ , or Gd 3+ , occupies the A site (16d) coordinated by 8 O atoms (6 on 48f sites and 2 on 8b sites), and Zr 4+ occupies the B site (16c) coordinated by 6 O atoms on 48f sites and 2 ordered vacancies on 8a sites. , The advantages of the ordered pyrochlore La 2 Zr 2 O 7 include high mechanical strength, low cost, and structural flexibility. , Because of such important physical and chemical properties, studying La 2 Zr 2 O 7 has a practical significance in the application of immobilizing actinides in this ceramic matrix.…”

Pyrochlore Rare-Earth Hafnate RE2Hf2O7 (RE = La and Pr) Nanoparticles Stabilized by Molten-Salt Synthesis at Low Temperature

“…There has been much effort on increasing surface area and decreasing grain size to the nanodomain in order to enhance sinterability and other optical, catalytic, and magnetic properties. 16,17 Along this line, the controlled morphology of NPs also influences the physical and chemical properties of materials and ultimately plays a major role in their applications. 17 To avoid problems associated with the common solid-state synthesis method, several wet-chemistry based synthetic routes have been reported for the preparation of this type of ternary oxide nanomaterials.…”

“…16,17 Along this line, the controlled morphology of NPs also influences the physical and chemical properties of materials and ultimately plays a major role in their applications. 17 To avoid problems associated with the common solid-state synthesis method, several wet-chemistry based synthetic routes have been reported for the preparation of this type of ternary oxide nanomaterials. Wet-chemistry methods involve mixing precursors at the molecular level, thus producing materials with high compositional homogeneity and stoichiometric control.…”

“…Furthermore, high surface area mixed metal oxide nanoparticles (NPs) exhibit superior physical and chemical properties compared to their bulk counterparts. There has been much effort on increasing surface area and decreasing grain size to the nanodomain in order to enhance sinterability and other optical, catalytic, and magnetic properties. , Along this line, the controlled morphology of NPs also influences the physical and chemical properties of materials and ultimately plays a major role in their applications …”

Rare-Earth Zirconate Ln2Zr2O7 (Ln: La, Nd, Gd, and Dy) Powders, Xerogels, and Aerogels: Preparation, Structure, and Properties

“…Some of these materials can undergo an order–disorder phase transformation from pyrochlore to fluorite at temperatures beyond 1500 °C. This temperature transition strongly depends on the nature of the rare-earth ion along with the sample processing; for example, Nd 2 Zr 2 O 7 , Sm 2 Zr 2 O 7 , and Gd 2 Zr 2 O 7 undergo transitions between 1530 and 2300 °C. − The lanthanide zirconate La 2 Zr 2 O 7 undergoes a structural transformation under high-pressure conditions. , Typically, these materials can be prepared by a variety of synthetic methodologies (e.g., co-precipitation, sol–gel, molten salts, and combustion techniques; see Table S1 in the Supporting Information) that eventually lead to different chemical homogeneity, phase composition, and crystallite size. − …”