Structural stability of the robust GdYTi2O7 pyrochlore under high pressure

Complex ceramics with pyrochlore (A(2)B(2)O(7)) and defect-fluorite ((A, B)(4)O-7) type structures experience structural modifications under high pressure. Here, we used mechanical milling and sintering followed by compression in diamond anvil cell to determine the high-pressure behavior using in-situ synchrotron diffraction. Raman spectroscopy and X-ray diffraction at ambient pressure confirm the pyrochlore phase of as-prepared GdYTi2O7 ceramic. In-situ high-pressure experiments reveal no structural phase transition in GdYTi2O7 pyrochlore up to approximately 50 GPa. The variation in the x positional coordinate of O-48f oxygen and cation-anion bond lengths shows that disordering occurs at high pressure above similar to 43 GPa. The Rietveld refinement results indicate the pyrochlore phase of GdYTi2O7 ceramic at the highest pressure of similar to 50 GPa. Compared to Y2Ti2O7, the equal substitution of Y3+ and Gd3+ at the A-site increases phase stability at high pressures. The experimental results indicate that mainly cation disordering occurs with increasing pressure, and lower compressibility of < Ti-O-48f > bonds should play a significant role in the robustness of GdYTi2O7 pyrochlore to sustain pyrochlore structure up to very high pressures. DFT-derived cation-anion bond lengths and bulk modulus value agree with the experimental results in supporting the robustness of the GdYTi2O7 pyrochlore.