Room temperature stabilization of the cubic phase of CuCr2O4 and CuFe2O4 in composites

Composites of spinel oxides, CuCr2O4 and CuFe2O4, with the polymer poly-aryl-ether-ether-ketone (PEEK) were prepared and the phase transitions of the high temperature cubic forms were studied. Characterization of the quenched CuCr2O4 composite samples by X-ray diffraction (XRD) indicates that cubic CuCr2O4 is obtained by quenching the composite samples from temperatures above 853 K, due to hindrance of the cubic → tetragonal fast phase transition by the polymer matrix present in the composite. The XRD results of the quenched CuFe2O4 composite samples show that cubic CuFe2O4 was obtained by quenching the composite samples from lower temperatures (∼733 K). This is due to the process of lower-temperature quenching-in of both Cu2+oct/Cu2+tet and oxygen vacancies necessary for the formation of the cubic phase.