PURPOSE: To obtain a vitreous compsn. having superior uniformness and moldability and exhibiting high conductivity for Na+ ion by mixing Na2O, ZrO2, P2O5, and SiO2.

CONSTITUTION: A vitreous compsn. contains 15W30mol% Na2O, 15W25mol% ZrO2, 10W20mol% P2O5, and 20W60mol% SiO2, wherein the vitreous compsn. means an opaque glass or glass ceramic. The compsn. is very easily soluble and vitrifiable, and the glass obtd. therefrom has good conductivity for Na+ ion. Further, a strong glass ceramic is obtd. easily by the heat treatment,and the conductivity for Na+ ion is higher by 101W102 order (Scm-1) than the original glass. oxides or their precursors of each component, pref. SiO2, ZrSiO4, NaH2PO4, H3PO4, Na2CO3, NaOH, etc., are used for the compsn.