Crystal material and method of manufacturing the same

A crystal material manufacturing method comprising:

• a first step of preparing a raw material mixture by mixing a carbonate or oxide of an alkaline-earth metal, an oxide of Nb or Ta or a mixture of an Nb oxide and a Ta oxide, an oxide of Ga, a carbonate or oxide of RE, and Si or an oxide thereof, so as to obtain each cation ratio indicated by any desired congruent composition of AE3ME1+a(Ga1−xREx)3+bSi2+cO14 (AE is an alkaline-earth metal, ME is Nb or Ta, RE is at least one of Y, Sc, and lanthanoide, 0≤x≤1, −0.5<a<0.5, −0.5<b<0.5, and −0.5<c<0.5);
• a second step of melting the raw material mixture;
• and
• a third step of forming a crystal material made of a langasite-based oxide having the desired congruent composition by cooling the melted raw material mixture, and
• wherein AE=Ca, ME=Ta, and RE=Sc, and a≠0.0, b≠0.0, and c≠0.0.