The porous ceramic composition and method of preparation

A porous ceramic composition having improved thermal stability is comprised of ceramic grains bonded together by a grain boundary phase comprised of silica, rare earth element that is Eu, Gd, Nd or mixture thereof and oxygen and optionally yttrium, wherein the grain boundary phase has a amount of an alkali, an alkaline earth metal and a transition metal other than yttrium that is at most 2% by weight of the grain boundary phase.