Pressure-Induced Disordering and Anomalous Lattice Expansion inLa2Zr2O7Pyrochlore

Pressure-induced cation and anion disordering in ${\mathrm{La}}_{2}{\mathrm{Zr}}_{2}{\mathrm{O}}_{7}$ pyrochlore is quantitatively analyzed by Rietveld refinement of in situ x-ray diffraction patterns, Raman, and infrared measurements. An anomalous lattice expansion and obvious change of the pressure dependence of the vibrational modes occur at $\ensuremath{\sim}10\text{ }\text{ }\mathrm{GPa}$. The pressure-induced water incorporation in the ${\mathrm{La}}_{2}{\mathrm{Zr}}_{2}{\mathrm{O}}_{7}$ pyrochlore structure may be related to a previously noted photoelectrochemical effect.