Lanthanum calcium chromate ceramics are composed of chromium oxide, lanthanum oxide and calcium oxide, lead lanthanum zirconate titanate (PLZT) ceramics are composed of zirconium oxide, titanium oxide, lead oxide, and lanthanum oxide. In addition, there is a large class of cermets formed by adding metals to ceramics, such as oxide-based cermets, carbide-based cermets, boride-based cermets, etc., which are also important varieties in modern ceramics.