The structural changes and magnetoresistance (MR) properties of as-grown and post-annealed La0.7Ca0.3MnO3 films were investigated by transmission electron microscopy (TEM) and x-ray diffraction (XRD). The data for the films were compared to that for bulk La0.7Ca0.3MnO3 post-annealed under the same conditions. The main structure of the as-grown films was face-centered pseudo-cubic with a doubled perovskite unit cell, of size ∼2ap × ∼2ap × 2ap, where ap is the single perovskite parameter. The phase showed a cube-on-cube epitaxy with the underlying LaAlO3 substrate. Upon annealing to a saturation point, a minor primitive pseudo-tetragonal structure evolved, of cell parameters . A total of four possible orientations of the two structures was observed by TEM, comprised of one orientation of the ∼ 2ap × ∼ 2ap × ∼ 2ap cell, i.e., the cube-on-cube epitaxy, giving rise to (00l) peaks in x-ray, and three orientations of the cell, giving rise to a single (00l)/(hk0) peak in x-ray. The bulk La0.7Ca0.3MnO3 sample also contains the × structure. The difference between the bulk and the film and the effects of annealing on films can be ascribed to the influence of strain between the film and substate, induced by lattice mismatch.

The upper stability line for Bi2Sr2CaCu2O8+α (Bi‐2212) was determined over the temperature range 540°–800°C and the oxygen partial pressure range 1.5 ×101‐7.4× 10‐3 atm using coulometric titration and high oxygen pressure annealing. The decomposition products resulting from Bi‐2212 oxidation are CuO, two alkaline‐earth bismuthates, and the Raveau phase, Bi11Sr9Cu5Oy. The main alkaline‐earth bismuthate is a known phase of cation composition Bi:Sr:Ca = 2.00:2.48:1.19 (Bi:Sr:Ca 9:11:5). The other alkaline‐earth bismuthate is a minor phase of cation composition Bi:Sr:Ca = 2.00:0.53:0.39. The kinetics for Bi‐2212 decomposition are very slow; e.g., at 700°C in air, the reaction is incomplete after 7 days.

The growth process of a YBCO͞LaAlO 3 ͞YBCO trilayered film made by pulsed laser deposition has been studied by high resolution transmission electron microscopy (HRTEM). The high resolution images of the cross-section samples have shown that a 7 nm layer of LaAlO 3 has been grown epitaxially between c-axis oriented YBCO layers having the nominal thickness of 250 nm. A stacking fault in the LaAlO 3 layer may introduce a stacking fault into the YBCO layer, which may form nucleation sites for a-axis oriented grains. A second phase had been formed at the interface between the LaAlO 3 layer and the lower YBCO layer, which has been identified by image simulation and energy dispersive x-ray (EDX) analysis as a new tetragonal La-Al-Cu-O phase based on LaAlO 3 in which some of Al atoms have been replaced by Cu. The approximate lattice parameters of the new phase are a 0.38 nm and c 0.76 nm. However, no second phase was found at the interface between the lower YBCO layer and the LaAlO 3 substrate.

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