Xiao-Dong Sun

A combinatorial approach to materials discovery

A method that combines thin film deposition and physical masking techniques has been used for the parallel synthesis of spatially addressable libraries of solid-state materials. Arrays containing different combinations, stoichiometries, and deposition sequences of BaCO3, Bi2O3, CaO, CuO, PbO, SrCO3, and Y2O3 were generated with a series of binary masks. The arrays were sintered and BiSrCaCuO and YBaCuO superconducting films were identified. Samples as small as 200 micrometers by 200 micrometers in size were generated, corresponding to library densities of 10,000 sites per square inch. The ability to generate and screen combinatorial libraries of solid-state compounds, when coupled with theory and empirical observations, may significantly increase the rate at which novel electronic, magnetic, and optical materials are discovered and theoretical predictions tested.

A Class of Cobalt Oxide Magnetoresistance Materials Discovered with Combinatorial Synthesis

The recent development of methods for generating libraries of solid-state compounds has made it possible to apply combinatorial approaches to the discovery of materials. A library of 128 members containing different compositions and stoichiometries of LnxMyCoOδ, where Ln = Y or La and M = Pb, Ca, Sr, or Ba, was synthesized by a combination of thin-film deposition and physical masking techniques. Large magnetoresistance has been found in Lax(Ba,Sr,Ca)y-CoOδ samples, whereas Y-based samples exhibit much smaller magnetoresistive effects. The magnetoresistance of the Co-containing compounds increases as the size of the alkaline earth ion increases, in sharp contrast to Mn-containing compounds, in which the magnetoresistance effect increases as the size of the alkaline earth ion decreases.

Identification and optimization of advanced phosphors using combinatorial libraries

A combination of thin-film deposition and physical masking steps were used to generate libraries of the rare earth activated refractory metal oxides, Gd(La,Sr)AlOx. Systematic variation of composition and processing conditions afforded tricolor phosphors with the following nominal compositions, (Gd0.46Sr0.31)Al1.23OxF1.38:Eu0.062+ (green), La0.5Al1.5Ox:Eu0.042+ (blue), and Gd0.77Al1.23Ox:Eu0.063+ (red), which had quantum efficiencies of ⩾94%, ≃60%, and ⩾93%, respectively at λmaxex. The high quenching temperatures (250–350 °C), good chromaticities and refractory nature of these phosphors are desirable features for display applications.

Synchrotron x-ray microbeam diagnostics of combinatorial synthesis

X-ray microbeam techniques (spot size=3×20 μm2) have been applied to characterize the composition and structure of rare earth activated Gd(La, Sr)AlO3 phosphor thin films grown by combinatorial synthesis. Using x-ray fluorescence, x-ray diffraction and near-edge x-ray absorption spectroscopy, we have measured the chemical composition, crystallographic structure, and valence state of the rare earth activator atom Eu. These measurements represent the direct application of x-ray techniques to solid-state materials prepared by combinatorial synthesis and demonstrate the power of x-ray microbeam analysis to nondestructively characterize as-grown combinatorial libraries.

New phosphor (Gd2−xZnx)O3−δ:Eu3+ with high luminescent efficiency and superior chromaticity

A new phosphor, (Gd{sub 1.54}Zn{sub 0.46})O{sub 3{minus}{delta}}:Eu{sub 0.06}{sup 3+}, with a photoluminescent quantum efficiency of {approx}86{percent} and a superior color chromaticity (x=0.656, y=0.344) compared to the state of art red phosphor Y{sub 2}O{sub 3}:Eu{sup 3+} was identified using the combinatorial thin film synthesis method. This phosphor may replace Y{sub 2}O{sub 3}:Eu{sup 3+} in display applications where a more saturated red phosphor is preferred. {copyright} {ital 1998 American Institute of Physics.}