The invention relates to a metal-ceramic substrate and to a method for the production thereof, the substrate including at least one ceramic layer having first and second surface sides, at least one of the surface sides of which is provided with a metallization, wherein the ceramic material forming the ceramic layer contains aluminum oxide, zirconium dioxide and yttrium oxide. The ceramic layer contains aluminum oxide, zirconium dioxide and yttrium oxide in the following proportions, in each case in relation to the total weight thereof: zirconium dioxide between 2 and 15 percent by weight; yttrium oxide between 0.01 and 1 percent by weight; and aluminum oxide between 84 and 97 percent by weight, wherein the average grain size of the aluminum oxide used is between 2 and 8 micrometers and the ratio of the length of the grain boundaries of the aluminum oxide grains to the total length of all the grain boundaries is greater than 0.6.