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New high-performance ferroelectric materials based on Pb(Zr{sub 1-x}Ti{sub x})O{sub 3} (PZT) that are doped with cryolite-type strontium niobate (SNO, Sr{sub 4}(Sr{sub 2-2y/3}Nb{sub 2+2y/3})O{sub 11+y}V{sub 0,1-y} with 0 {le} y {le} 1), hence denoted PZT:SNO, and their microscopic structure are described. The combination of exceptional piezoelectric properties, i.e. a piezoelectric strain constant of d{sub 33} {approx} 760 pm/V, with excellent stability and degradation resistance makes ferroelectric PZT:SNO solid solutions very attractive for use in novel and innovative piezoelectric actuator and transducer applications. Extended X-ray absorption fine-structure (EXAFS) analyses of PZT:SNO samples revealed that {approx}10 % of the Sr cations occupy the nominal B-sites of the perovskite-type PZT host lattice. This result was supported by EXAFS analyses of both a canonical SrTiO{sub 3} perovskite and two SNO model and reference compounds. Fit models that do not account for Sr cations on B-sites were ruled out. A clear Sr-Pb peak in Fourier transformed EXAFS data visually confirmed this structural model. The generation of temporary oxygen vacancies and the intricate defect chemistry induced by SNO-doping of PZT are crucial for the exceptional materials properties exhibited by PZT:SNO materials.

We present K-edge x-ray absorption fine structure (XAFS) data for and the local structure of several Y 1− x Pr x Ba 2 Cu 3 O 7 alloys. Most of the Pr substitutes onto well ordered Y sites. The amplitude of the first Pr-O peak is greatly reduced when compared to the first Y-O peak. Fits to standards suggest that some oxygen atoms around the Pr become disordered. Most of the Pr-O distances are about 2.45 A, but 15−40% of them are in a somewhat broadened peak at about 2.27 A. The existence and the size of these two bond lengths is consistent with a hybridization of Pr 3+ , Pr 4+ , and (Pr 3+ — hole-in-the-ligand) bonds and a formal valence of about 3.33+ for the Pr ion.

The effect of some systematic errors for high-precision time-series spaceborne photometry and astrometry has been investigated with a CCD as the detector. The 'pixelization' of the images causes systematic error in astrometric measurements. It is shown that this pixelization noise scales as image radius r exp -3/2. Subpixel response gradients, not correctable by the 'flat field', and in conjunction with telescope pointing jitter, introduce further photometric and astrometric errors. Subpixel gradients are modeled using observed properties of real flat fields. These errors can be controlled by having an image span enough pixels. Large images are also favored by CCD dynamic range considerations. However, magnified stellar images can overlap, thus introducing another source of systematic error. An optimum image size is therefore a compromise between these competing factors.

The coordination environments of Pt impurities in a ternary K-aluminophosphate (KAP) glass and commercial K,Mg-aluminophosphate (KMAP) laser glasses have been investigated by Pt L{sub III}-edge X-ray absorption fine structure (XAFS) spectroscopy. Pt valence in the KAP glass depends on the melt preparation atmosphere. Pt{sup 4+} ions form in melts that are bubbled with oxygen, whereas metallic Pt particles form when these same samples are remelted in air. Residual chlorine in KMAP glasses has an effect on Pt bonding. In chlorine-free samples, Pt{sup 4+} ions are coordinated with {approx}5.4 (8) oxygen atoms with an average distance of 2.02 (1) {angstrom}. For glasses with low chlorine contents ( 5, only Cl nearest neighbors are observed. Pt{sup 4+} ions in these latter glasses are coordinated by {approx}5.5 (8) Cl atoms at an average distance of 2.27 (2) {angstrom}.