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

In this work we report on the microwave assisted synthesis of nano-sized Gd2Ti2O7 (GTO) and Ho2Ti2O7 (HTO) powders from the RE2Ti2O7 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 °C, and the defects disappear at 1400 °C. 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.