Revisiting the Sr–Cr(IV)–O system at high pressure and temperature with special reference to Sr3Cr2O7

High pressure and temperature are used to synthesise perovskite related phases in the Sr–Cr(IV)–O system. The n = 1, 2 and ∞ members of the Sr_n+1Cr_nO_3n+1 family have been obtained. Another new member, n = 3 as well as an hexagonal layered perovskite have also been observed by transmission electron microscopy and electron diffraction. The average structure of Sr₃Cr₂O₇ as determined by XRD has space group I4/mmm, whereas its microstructure includes a large amount of defects both in the layer stacking and within the layers. 2D magnetism and a large electrical resistance in Sr₃Cr₂O₇ are observed as opposed to the nonlocalized electronic behaviour of SrCrO₃.