  Using 4-circle x-ray diffraction and transmission electron microscopy we have
studied the microstructure and in-plane orientation of the phases present in
thin film composite mixtures of YBa(2)Cu(3)O(7) and Y(2)O(3). We see a high
degree of in-plane orientation and have verified a previous prediction for the
in-plane order of Y(2)BaCuO(5) on (110) MgO. Transmission electron microscopy
shows the composite films to be a mixture of two phases, with YBCO grain sizes
of 1 micron. We have also compared our observations of the in-plane order to
the predictions of a modified near coincidence site lattice model.
