Anti-site disorder and physical properties in microwave synthesized RE₂Ti₂O₇ (RE = Gd, Ho) pyrochlores

Abstract

In this work we report on the microwave assisted synthesis of nano-sized Gd 2 Ti 2 O 7 (GTO) and Ho 2 Ti 2 O 7 (HTO) powders from the RE 2 Ti 2 O 7 pyrochlore family (RE = rare earth). Synchrotron X-ray powder diffraction was used to study RE-Ti cationic anti-site defects with concentrations that decrease in both samples with increasing temperature starting from 1100 ºC, and the defects disappear at 1400 ºC. SQUID magnetometry measurements revealed that GTO shows a predominantly anti-ferromagnetic structure, whereas HTO exhibits magnetic saturation and a ferromagnetic component at low temperature. Impedance spectroscopy data revealed strongly increased ionic oxygen vacancy conduction in HTO ceramic pellets as compared to GTO, which may be associated with a higher degree of oxygen vacancy disorder. This argument was supported by Raman spectroscopy data.

Multifunctional Gadolinium‐Doped Mesoporous TiO2 Nanobeads: Photoluminescence, Enhanced Spin Relaxation, and Reactive Oxygen Species Photogeneration, Beneficial for Cancer Diagnosis and Treatment

“…In the highest concentrations adopted here, TiO 2 @20%Gd, an outer crystalline structure is also formed ( Figure e) that likely can be attributed to the new crystalline phase apparent in the XRD pattern for this sample (Figure b). In the XRD pattern of TiO 2 @20%Gd NBs, the (105) and (213) peaks can be assigned to reflections from the anatase phase of TiO 2 , while the predominant phase for this structure is the pyrochlores phase, with (004) and (102) peaks that can be assigned to Gd 2 TiO 5 , and peak (551) assigned to Gd 2 Ti 2 O 7 (JCPDS number: 21‐1272) . In both figures, peaks named FTO (fluorine‐doped tin oxide conducting glass) are attributed to the sample substrate.…”

“…In the XRD pat tern of TiO 2 @20%Gd NBs, the (105) and (213) peaks can be assigned to reflections from the anatase phase of TiO 2 , while the predominant phase for this structure is the pyrochlores phase, with (004) and (102) peaks that can be assigned to Gd 2 TiO 5 , and peak (551) assigned to Gd 2 Ti 2 O 7 (JCPDS number: 211272). [38,39] In both figures, peaks named FTO (fluorinedoped tin oxide conducting glass) are attributed to the sample substrate.…”

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

“…The relationship between the urea concentration and the nal product can be explained by the pH variation. When the temperature of mixed solution increases, the hydrolysis reaction takes place and provides hydroxide ions described in eqn (1) and 2,…”

“…Gd 2 Zr 2 O 7 is one of the most important rare-earth-stabilized zirconia (RESZ) materials due to its potential application as a ceramic waste matrix for immobilizing actinides and ssion products. 1,2 This crystalline system has a general formula A 2 B 2 O 7 , with one eight-coordinated A site (16c) and one sixcoordinated B site (16d) that are capable of incorporating a large amount of radionuclides (e.g. Pu, U, Np, Hf, Th, Am and Cm).…”