A turbine nozzle assembly includes an inner circumferential support platform, an outer circumferential support platform, and a plurality of airfoil vanes disposed between the inner circumferential support platform and the outer circumferential support platform. The turbine nozzle assembly further includes a plurality of impingement plates disposed along a radially outer surface of the outer circumferential support platform or a radially inner surface of the inner circumferential support platform, and a plurality of gap-maintaining features disposed between the plurality of outer or inner circumferential support platforms and the plurality of impingement plates. Each gap-maintaining feature of the plurality of gap-maintaining features is provided at a height such that a cooling air flow space is maintained between the plurality of outer or inner circumferential support platforms and the plurality of impingement plates.