Niobium and niobium-titanium nitrides for RF applications

The application of niobium and niobium-titanium nitrides in RF devices is studied. Nitride samples, prepared by diffusion of nitrogen in bulk niobium and alloy, have been characterized by X-ray diffraction, SEM and AC magnetic measurements. Several phases of niobium nitride have been observed: the phase with higher nitrogen content, at the sample surface, has critical temperature about 15 K but inclusions of both lower T/sub c/ and nonsuperconducting phases enhance the RF surface resistance. The niobium-titanium nitride surface is composed by a phase having critical temperature up to 17 K and unwanted phases were not observed.<
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