High-pressure behavior and equations of state of the cobaltates YBaCo4O7, image, YBaCoZn3O7 and image

The compressibilities of the cobaltates YBaCo4O7, YBaCo4O7+δYBaCo4O7+δ, YBaCoZn3O7 and BaCoO3−xBaCoO3−x were investigated by in situ powder X-ray diffraction experiments up to 30 GPa using diamond anvil cells. Pressure-induced phase transitions and amorphization were observed in all the samples. The onset of the pressure-induced phase transition and the onset of the amorphization were observed at ∼11.7∼11.7 and 12.2 GPa (YBaCo4O7), at ∼14.2∼14.2 and 16.1 GPa (YBaCo4O7+δYBaCo4O7+δ), and at ∼16.7∼16.7 and 18.7 GPa (YBaCoZn3O7), respectively. An attempt to laser anneal at high-pressure failed as it led to a decomposition of the YBaCo4O7 phase into a mixture of phases. Fits of second- and third-order Birch–Murnaghan equations-of-state to the p–Vp–V data result in B 0=109(3) GPa for YBaCo4O7; B 0=186(4) GPa and B′=1.5B′=1.5 for YBaCo4O7+δYBaCo4O7+δ; and B0=117(1) GPa for YBaCoZn3O7. The high-pressure behavior of the studied compounds was compared with isostructural compounds and it is shown that the oxygen-content has a very large effect on the high-pressure behavior of this class of materials.