INCOMMENSURATE MODULATED STRUCTURE AND PLANAR FAULTS OF A PHASE WITHIN Y2-XCAXCU2O5 MATERIAL WITH X=0.1, 0.2 AND 0.4

A phase with incommensurate modulated structure has been found within samples of Y2-xCaxCu2O5 where x=0.1, 0.2 and 0.4. This phase becomes t he main phase within the Y1.6Ca0.4CU2O5 sample. Using higher-dimension al space groups, the lattice parameters for this phase are a approxima te to 2.12 nm, b approximate to 1.24 nm and c approximate to 0.56 nm w ith superspace group A Ammm/111. The wave vector of the modulation is K = 1/2a* + 0.3958c*. In addition, the crystals intergrow as parallel lamellae such that certain of the electron diffraction patterns are c haracteristic of those from twin crystals.