Investigation of polycrystalline diamond films by electron paramagnetic resonance at 9.5 and 35 GHZ has revealed the presence of forbidden transitions resulting from a simultaneous microwave induced flipping of unpaired electron spins and environmental nuclear spins. The spacing of the resonance lines identifies hydrogen as the atom neighboring the paramagnetic active site.
Composite thick films of YBa2Cu3O7−x and silver have been prepared on alumina substrates using a paint-on method. It is found that thick films containing greater than about 10% silver by weight have greatly reduced normal resistivities for T>Tc (onset) and significantly enhanced Tc (R=0) as compared with undoped films processed under identical conditions. These results are interpreted in terms of enhanced grain growth and an improved coupling between grain boundaries because of proximity-induced electron pairing in the silver regions.
We show that semiconducting and insulating metal-oxide phases emit substantially greater luminescence when irradiated with 10–30 keV electrons than metallic, candidate high Tc superconducting phases. The use of a cathodoluminescence (CL) detector in a scanning electron microscope to form high-resolution CL images of Y2O3, BaCO3, Y2BaCuO5, oxygen-depleted YBa2Cu3O7−x(x>0.5), and oxygen-annealed YBa2Cu3O7−x(x∼0) is reported. The spatial resolution obtained in CL micrographs of YBa2Cu3O7−x is found to be about 0.1 μm when the electron beam current is 190 nA. The use of CL microscopy in combination with energy-dispersive x-ray analysis may be a promising technique for identifying candidate superconducting phases of novel stoichiometry in complex multiphase samples.
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