Embodiments of a turbine nozzle having slip joints impregnated by an oxidation-resistant sealing material are provided, as are embodiments of methods for the manufacture of turbine nozzles. In one embodiment, the method includes providing a support ring, a slip joint ring substantially concentric with the support ring and radially spaced apart therefrom, and a plurality of vanes fixedly coupled to the support ring. The plurality of vanes extends radially from the support ring into a plurality of circumferentially-spaced slots provided in the slip joint ring to form a plurality of slip joints therewith. The plurality of slip joints are impregnated with a silicon-modified aluminide sealing material. The silicon-modified aluminide sealing material impedes gas flow into the radial slip joints during operation of the turbine nozzle, while also fracturing to permit relative radial movement between the plurality of vanes and the slip joint ring along the plurality of slip joints.