Ceramic composite coating material

An internal combustion engine including a cylinder with a top side and a bottom side;

• a piston disposed in the cylinder such that the piston is free to move in the cylinder, wherein the piston has a piston crown that faces the top side of the cylinder;
• and a piston head firedeck that closes the top side of the cylinder, wherein the piston crown and piston head firedeck together define a variable volume combustion chamber in the cylinder;
• wherein the improvement comprises a thermal barrier coating on the piston crown comprising:
• (a) a metallic bond coat deposited on the piston crown,
• (b) at least one MCrAlY/ceramic layer deposited on the bond coat, wherein M is Fe, Ni, Co, or a mixture of Ni and Co, and the ceramic in the MCrAlY/ceramic layer comprises mullite, alumina, zircon, sillimanite, sodium zirconium phosphate, fused silica, cordierite, or aluminum titanate, and
• (c) a ceramic composite top layer deposited on the MCrAlY/ceramic layer, wherein the ceramic composite top layer comprises a ceramic with a coefficient of thermal expansion less than about 5.4.times.10.sup.-6 .degree.C..sup.-1 and a thermal conductivity between about 1 J sec.sup.-1 m.sup.-1 .degree.C..sup.-1 and about 1.7 J sec.sup.-1 m.sup.-1 .degree.C..sup.-1 and at least one secondary phase dispersed in the matrix such that the secondary phase inhibits crack propagation in the ceramic composite top layer.