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diffractometer with a Rigaku x-ray generator. A copper x-ray tube in conjunction with a Ni filter was used at a power setting of 2OmA and 45KV. The sample was placed in a hot stage constructed with a beryllium dome. Temperature was controlled using a Eurotherm 818S controller with a heating rate of 50°C/hour. Initially the PT film was heated to 510 °C and then cooled at a rate of 50°C/hour. (200). and (002), reflections were monitored by performing 0-20 scans as a function of temperature. Rocking curves (w-scans) were also performed on the (200). reflection at various temperatures. After detailed analysis of the initial cycle, the sample was repeatedly cycled 6 times; cycles 1-3 were heated below 400'C and cycles 4-6 were above 520°C, under similar conditions in order to compare domain structures as a function of temperature cycling. Data collected from the cycling experiments consisted primarily of domain size measurements of a and c domains using 020 scans of the (202). and (202). reflections. Rocking curves were also performed for the (200). reflection at each temperature. After temperature cycling, the domain structure was examined using high resolution transmission electron microscopy (HRTEM), and selected area diffraction pattern (SADP). Both planar and cross sectional views were taken. RESULTS AND DISCUSSION Figure 1(a) shows a cross-section HRTEM lattice image of the PT/MgO interface. This appears to be quite continuous indicating true epitaxial growth of PT on MgO(001). Three SADP inserts are included, each corresponds to a particular area of the overall picture. The pattern located in the upper right corner indicates the existence of both a and

Figure 1. (a)Cross-section HRTEM image of the PT/MgO interface (b) Planar view TEM image of the PT film, showing a and c domains.

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c domains due to the splitting of the (101) diffraction spots. The SADP of the actual interface shows alignment in high symmetry directions of the film and substrate. The lower insert is of the substrate alone aligned in the [001] direction. A planar view TEM image is shown in Figure 1(b) which clearly shows the 900 domains. Domain structures were further investigated by the XRD co scan, also known as the rocking curve, of the (200). peak. Three peaks were observed as shown in Figure 2, indicating a 2.2 degree separation between a-domain and c-domain at 27°C, which is consistent with the work by Gao et all. Figure 2 also shows the evolution of grain tilting (opposing grains) for the (200). reflections. As the temperature increases, the c/a ratio decreases, thereby reducing grain tilting. This tilting is thought to be due primarily to transformation strain, however some discrepancy between predicted values [(2tanl(c/a)900)] and experimental values may merit further study. 90 80

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Figure 2. Consecutive (200). co scans performed during heating. Figures 3(a) and 3(b) show lattice parameter measurements taken as a function of temperature (heating and co