We report the observation of periodic 180 degrees stripe domains below the ferroelectric transition in thin films. Epitaxial PbTiO3 films of thickness d=1.6 to 42 nm on SrTiO3 substrates were studied using x-ray scattering. Upon cooling below T(C), satellites appeared around Bragg peaks indicating the presence of 180 degrees stripe domains of period Lambda=3.7 to 24 nm. The dependence of Lambda on d agrees well with theory including epitaxial strain effects, while the suppression of T(C) for thinner films is significantly larger than that expected solely from stripe domains.

Possible domain patterns are developed for (001) oriented (pseudocubic indexing) epitaxial rhombohedral perovskite ferroelectric (FR) films. We assume that the films are grown above their Curie temperature (TC) in a cubic paraelectric (PC) state. The rhombohedral distortion consists of a “stretch” along one of the four 〈111〉 crystallographic directions of the cubic perovskite unit cell. Domain pattern formation is concurrent with the PC→FR transformation on cooling from the growth temperature. The domain patterns form to minimize elastic energy in the film, at the energetic expense of both forming domain boundaries and developing local stresses in the substrate. Eight possible domains may form, half of which are related by inversion, thus leading to four mechanically distinct variants. The possible domain walls are determined by mechanical and charge compatibility and follow closely from the analysis of Fousek and Janovec [J. Appl. Phys. 40, 135 (1969)]. Domain patterns may develop with either {100} or {101} boundaries. In both cases, the individual domains in the patterns are energetically degenerate and thus equal width lamellar patterns are predicted. When polarization is included in the analysis, the {100} boundary patterns have no normal component of the net polarization, whereas the {101} boundary patterns correspond to the fully poled state. We report on experimental observation of {100} domain patterns in epitaxial PbZr0.80Ti0.20O3 and PbZr0.65Ti0.35O3 films.

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Single-crystal thin films of Pb(ZrxTi1−x)O3 (PZT) covering the full compositional range (0⩽x⩽1) were deposited by metal-organic chemical vapor deposition. Epitaxial SrRuO3(001) thin films grown on SrTiO3(001) substrates by rf-magnetron sputter deposition served as template electrode layers to promote the epitaxial growth of PZT. X-ray diffraction, energy-dispersive x-ray spectroscopy, atomic force microscopy, transmission electron microscopy, and optical waveguiding were used to characterize the crystalline structure, composition, surface morphology, microstructure, refractive index, and film thickness of the deposited films. The PZT films were single crystalline for all compositions exhibiting cube-on-cube growth epitaxy with the substrate and showed very high degrees of crystallinity and orientation. The films exhibited typical root mean square surface roughness of ∼1.0–2.5 nm. For tetragonal films, the surface morphology was dominated by grain tilting resulting from ferroelectric domain formation. We report the systematic compositional variation of the optical, dielectric, polarization, and electronic transport properties of these single-crystalline PZT thin films. We show that the solid-solution phase diagram of the PZT system for thin films differs from the bulk due to epitaxy-induced strains and interfacial defect formation. High values of remanant polarization (30–55 μC/cm2) were observed for ferroelectric compositions in the range of 0.8⩽x⩽0.2. Unlike previous studies, the dielectric constant exhibited a clear dependence on composition with values ranging from 225 to 650. The coercive fields decreased with increasing Zr concentration to a minimum of 20 kV/cm for x=0.8. The undoped films exhibited both high resistivity and dielectric-breakdown strength (1013–1014 Ω cm at 100 kV/cm and 300–700 kV/cm, respectively).

A grain-size-dependent reduction in the room-temperature thermal conductivity of nanocrystalline yttria-stabilized zirconia is reported for the first time. Films were grown by metal-organic chemical vapor deposition with controlled grain sizes from 10 to 100 nm. For grain sizes smaller than approximately 30 nm, a substantial reduction in thermal conductivity was observed, reaching a value of less than one-third the bulk value at the smallest grain sizes measured. The observed behavior is consistent with expectations based on an estimation of the phonon mean-free path in zirconia. © 2000 American Institute of Physics. ͓S0003-6951͑00͒05034-8͔The efficiency of gas turbine engines is dictated by the maximum sustained operating temperature of their typically Ni-or Co-based alloy turbine rotors. The development of new, higher temperature, high-strength, lightweight alloys is desirable. 1 However, recent studies have concluded that significant near-term progress in increasing turbine engine operating temperatures is more likely to come from the development of improved thermal barrier coatings ͑TBCs͒, typically yttria-stabilized zirconia ͑YSZ͒, than from the design of new alloys. 2 New processing techniques that result in TBC microstructures with lower thermal conductivity could lead either to higher operating temperatures of turbine engines, resulting in greater efficiency, or thinner coatings for the same operating temperature, which would reduce overall weight. Nanocrystalline YSZ coatings are of interest because they offer the possibility of lowering thermal conductivity, and may also provide additional benefits for TBC applications because of the possibility of improved toughness and ductility compared to that of coarser-grained ceramics. 3,4 The low thermal conductivity of YSZ ͑ϳ2.3 W/mK for high-density, polycrystalline material with a yttria-content of 10 mol. % at 20°C 5 ͒ is due primarily to phonon scattering by vacancies on the material's highly defective oxygen sublattice. 6 The potential for reduced thermal conductivity in nanocrystalline coatings arises from the predicted enhanced phonon scattering due to the presence of numerous closely spaced grain boundaries. For example, Klemens and Gell 6 have theoretically predicted that the room temperature thermal conductivity of 10 nm grain-sized YSZ containing 7 wt. % Y 2 O 3 will be decreased more than 50% compared to 1 m grain-sized YSZ of the same composition. The goal of the present study was to experimentally determine the effect of grain size on the room-temperature thermal conductivity of YSZ, thus contributing to the fundamental understanding of grain-size-dependent phonon scattering processes.Nanocrystalline YSZ films were grown by metal-organic chemical vapor deposition ͑MOCVD͒ using a low-pressure, horizontal, cold-walled deposition system. Yttrium b-diketonate ͓Y͑thd͒ 3 ͔ and zirconium t-butoxide ͓ZrOC͑CH 3 ͒ 4 ͔ 7 were chosen as precursor materials. Highpurity nitrogen was used as the precursor carrier gas. The precursors were mixed with high-purity ...