A high thermal emittance coating for an x-ray tube anode target which permits broad application parameters and a stable and smooth coating. The coating is composed of ZrO.sub.2 present in an amount of 8% to 20% by weight and Al.sub.2 O.sub.3 and TiO.sub.2 present in an amount of 92% to 80% by weight with the Al.sub.2 O.sub.3 and TiO.sub.2 being present in a ratio in the range of 4 to 1. A preferable coating is composed of about 10% by weight of ZrO.sub.2 and 90% by weight of Al.sub.2 O.sub.3 and TiO.sub.2.