Order–Disorder Phenomena in the Perovskite-Related Oxyborocarbonates SrMn1-y(B, C)yO3-

The electron diffraction and high-resolution electron microscopy investigation of the oxyborocarbonate SrMn1-y(C, B)yO3shows that the carbonate and borate groups substitute for the MnO6 octahedra in the perovskite matrix, according to a mechanism based on the intergrowth and microtwinning of two basic mother structures, Sr5Mn4CO3O10 (S5M4C) and Sr4Mn3BO3O7 (S4M3B). The two structures, S5M4C and S4M3B, coexist in the same matrix in the form of intergrowths, whose coherent boundaries are parallel to the {210}P planes of the perovskite structure. It results in the formation of {210}P antiphase boundaries and diamond-shaped domains are formed by combining twinning and intergrowth phenomena. These structural phenomena are compared to the microdomain and concentration wave models observed in alloys. These oxides are antiferromagnetic with TN=250 K, but weak ferromagnetic couplings are detected below 100 K.