PURPOSE: To increase fluorine ion conductivity, improve decrease of ion conductivity and thermal instability in air atmosphere to provide high ion conductivity by containing lithium fluoride in lead fluoride.

CONSTITUTION: Lithium fluoride is contained in lead fluoride. For example, 0.1∼50mol%, preferably 1∼30mol% LiF powder having a purity of 99.9% or more is mixed to PbF powder having a purity of 99.9% or more to obtain a raw material powder. When LiF powder less than 0.1mol% is used, mixing effect of LiF is decreased and LiF exceeding 50mol% decrease ion conductivity. The sintering method requires the raw material powder having a particle size of 50∼500 mesh. When a particle size is larger than 50 mesh, sintering effect is insufficient, and mixing effect of LiF is decreased. When a particle size is smaller than 500 mesh, uniform mixing is difficult and mixing of LiF is adversely affected.