Synthesis of Er2Ir2O7 pyrochlore iridate by solid-state-reaction and CsCl flux method

The solid-state reaction, hydrothermal synthesis and CsCl flux methods were employed preparing Er2Ir2O7 pyrochlore iridate. A mixture of initial Er2O3 and IrO2 oxides was thermally treated, following the temperature evolution of individual phases by means of x-ray diffraction and energy dispersive x-ray spectroscopy. Reactions by hydrothermal synthesis, using various commonly used mineralising agents, showed negligible increase in the pyrochlore phase fraction. The solid-state reaction method allowed a preparation of Er2Ir2O7, however the reacted mixture contained a high percentage (60%) of initial unreacted Er2O3. Adding an excess of IrO2 to the initial content improved the composition of the reacted sample (50% of Er2Ir2O7 for initial Er2O3:IrO2 ratio 0.9:2.1). Nevertheless, a secondary Er-Ir-O phase with slightly larger crystallographic unit cell was also created as an additional product. An optimised flux synthesis, consisting of repeated heating and regrinding cycles at 800 degrees C and using CsCl as a flux, provided the best conditions for single phase pyrochlore preparation. A sample with 94% Er2Ir2O7 was further improved by repeated reaction with additional excess IrO2 oxide. A successful preparation route for (at least) the heavy-rare earth pyrochlore iridates is established.

Automated summary

The solid-state reaction, hydrothermal synthesis, and CsCl flux methods were employed to prepare Er2Ir2O7 pyrochlore iridate, with the flux method providing the best conditions for single phase pyrochlore preparation. The purity of the sample reached 94% after repeated reaction with additional excess IrO2 oxide. A successful preparation route for heavy-rare earth pyrochlore iridates is established.