New pressure induced phase transitions in mullite-type Bi2(Fe4-xMnx)O10-δ complex oxides

Single phased mullite-type Bi2Fe4–xMnxO10–δ mixed crystals (0.25 ≤ x ≤ 3.125) and the end-member Bi2Fe4O9, synthesized from the oxides by reaction sintering up to 825°C, were studied at high-pressures in order to probe their high-pressure behavior and any possible structural phase transitions. In-situ synchrotron radiation-based powder X-ray diffraction was carried out in a diamond anvil cell, under quasi-hydrostatic conditions, up to a pressure of about 20 GPa at room temperature for each sample. A pressure-induced phase transition was found in all samples. The transition appeared spread over a pressure range and was not completed at the top investigated pressure. This is the first report of a pressure-induced phase transition in Bi2Fe4–xMnxO10–δ mixed crystals.