Surface impedance measurements in ${\mathrm{La}}_{1.8}$${\mathrm{Ba}}_{0.2}$${\mathrm{CuO}}_{4\mathrm{-}\mathrm{y}}$

Surface impedance measurements at 102 GHz are reported for the high-$T_c$ superconductor ${\mathrm{La}}_{1.8}$ ${\mathrm{Ba}}_{0.2}$ ${\mathrm{CuO}}_{4\mathrm{-}\mathrm{y}}$. In the superconducting state the temperature dependence of the surface resistance $R_s$ is in agreement with a Bardeen-Cooper-Schrieffer form and magnitude of the gap Δ(T). A distribution of gap values was found which is consistent with the smeared transition in the dc resistivity.