Synthesis of large Rare Earth Element Germanate Pyrochlore Single Crystals at High-Pressure

We report the successful synthesis of up to millimeter-size single crystals of the pyrochlore rare earth element (RE) germanates Dy2Ge2O7 and Ho2Ge2O7. Crystals were grown from oxide starting materials with the addition of 0.2 to 0.9 wt % H2O in sealed AuPd capsules at 7.7 GPa and 1200-1400 degrees C with a Belt-type high-pressure apparatus. With the use of seed crystals, regular, octahedrally-shaped crystals up to a size of 0.9 mm edge-length could be recovered.