An optical glass comprising: by mass%, 20% or more and 55% or less of a content rate of P.sub.2O.sub.5; 10% or more and 40% or less of a content rate of TiO.sub.2; 0% or more and 30% or less of a content rate of Nb.sub.2O.sub.5; 0% or more and 2% or less of a content rate of Al.sub.2O.sub.3; 0% or more and 10% or less of a content rate of B.sub.2O.sub.3; 3% or more and 30% or less of a content rate of BaO; 0% or more and 30% or less of a content rate of Bi.sub.2O.sub.3; 0% or more and 20% or less of a content rate of Ta.sub.2O.sub.5; and 0% or more and 25% or less of a content rate of WO.sub.3, wherein a ratio of a total content rate of Li.sub.2O, Na.sub.2O and K.sub.2O (ΣA.sub.2O; where, A = Li, Na and K) to a content rate of TiO.sub.2 (ΣA.sub.2O/TiO.sub.2) is 0.10 or more and 0.65 or less, and a ratio of a content rate of TiO.sub.2 to a total content rate of P.sub.2O.sub.5, B.sub.2O.sub.3, and Al.sub.2O.sub.3 (TiO.sub.2/(P.sub.2O.sub.5 + B.sub.2O.sub.3 + Al.sub.2O.sub.3) ) is 0.25 or more and 0.85 or less.

An optical glass comprising: by mass%, 20% or more and 55% or less of a content rate of P.sub.2O.sub.5; 10% or more and 40% or less of a content rate of TiO.sub.2; 0% or more and 30% or less of a content rate of Nb.sub.2O.sub.5; 0% or more and 2% or less of a content rate of Al.sub.2O.sub.3; 0% or more and 10% or less of a content rate of B.sub.2O.sub.3; 3% or more and 30% or less of a content rate of BaO; 0% or more and 30% or less of a content rate of Bi.sub.2O.sub.3; 0% or more and 20% or less of a content rate of Ta.sub.2O.sub.5; and 0% or more and 25% or less of a content rate of WO.sub.3, wherein a ratio of a total content rate of Li.sub.2O, Na.sub.2O and K.sub.2O (ΣA.sub.2O; where, A = Li, Na and K) to a content rate of TiO.sub.2 (ΣA.sub.2O/TiO.sub.2) is 0.10 or more and 0.65 or less, and a ratio of a content rate of TiO.sub.2 to a total content rate of P.sub.2O.sub.5, B.sub.2O.sub.3, and Al.sub.2O.sub.3 (TiO.sub.2/(P.sub.2O.sub.5 + B.sub.2O.sub.3 + Al.sub.2O.sub.3) ) is 0.25 or more and 0.85 or less.

A filter glass contains >1.1 to 6.0 wt % Li.sub.2O and at least one further component selected from Na.sub.2O and K.sub.2O, and includes the following composition (in wt % based on oxide): 55.0-75.0 P.sub.2O.sub.5, 4.1-8.0 Al.sub.2O.sub.3, 8.0-18.0 CuO, 0-<0.8 V.sub.2O.sub.5, ≤2.0 SiO.sub.2, ≤2.0 F, 0-11.0 Total R′O (R′=Mg, Ca, Sr, Ba, Zn), and 3.0-17.0 Total R.sub.2O (R=Li, Na, K).

A filter glass contains >1.1 to 6.0 wt % Li.sub.2O and at least one further component selected from Na.sub.2O and K.sub.2O, and includes the following composition (in wt % based on oxide): 55.0-75.0 P.sub.2O.sub.5, 4.1-8.0 Al.sub.2O.sub.3, 8.0-18.0 CuO, 0-<0.8 V.sub.2O.sub.5, ≤2.0 SiO.sub.2, ≤2.0 F, 0-11.0 Total R′O (R′=Mg, Ca, Sr, Ba, Zn), and 3.0-17.0 Total R.sub.2O (R=Li, Na, K).

An optical glass comprising: by mass %, 20% or more and 50% or less of a content rate of P.sub.2O.sub.5; 12.66% or more and 35% or less of a content rate of TiO.sub.2; 0% or more and 20% or less of a content rate of Nb.sub.2O.sub.5; and 5% or more and 30% or less of a content rate of Bi.sub.2O.sub.3, wherein a ratio of a content rate of TiO.sub.2 to a content rate of P.sub.2O.sub.5 (TiO.sub.2/P.sub.2O.sub.5) is 0.30 or more and 0.75 or less.

Provided is optical glass in which a refractive index nd is 1.900 or more, an Abbe number vd is 25.0 or less, an amount of P.sub.2O.sub.5 is 5.0 mass % or more, an amount of Bi.sub.2O.sub.3 is 20.0 mass % or less, an amount of TiO.sub.2 is 0.1 mass % or more, a mass ratio [TiO.sub.2/(Li.sub.2O+Na.sub.2O+K.sub.2O)] between the amount of TiO.sub.2, and a total amount of Li.sub.2O, Na.sub.2O, and K.sub.2O [Li.sub.2O+Na.sub.2O+K.sub.2O] is 2.5 to 10.0, a mass ratio [TiO.sub.2/(MgO+CaO+ZnO+SrO+BaO)] between the amount of TiO.sub.2 and a total amount of MgO, CaO, ZnO, SrO, and BaO [MgO+CaO+ZnO+SrO+BaO] is 1.25 to 10.0, and a mass ratio [(Li.sub.2O+Na.sub.2O+MgO+CaO+ZnO+SrO)/(K.sub.2O+BaO)] between a total amount of Li.sub.2O, Na.sub.2O, MgO, CaO, ZnO, and SrO [Li.sub.2O+Na.sub.2O+MgO+CaO+ZnO+SrO] and a total amount of K.sub.2O and BaO [K.sub.2O+BaO] is 0.8 or less.

As a solid electrolyte used in a lithium ion secondary battery, it has not been possible to obtain a lithium ion conductor precursor glass and a lithium ion conductor in which crystallization progresses at low temperatures and which exhibit high ion conductivity. The present invention can obtain a lithium ion conductor precursor glass and a lithium ion conductor in which crystallization progresses even at low temperatures and which exhibit high ion conductivity by containing 10-35% of a Li.sub.2O component, 20-50% of a P.sub.2O.sub.5 component, greater than 0% to 15% of an Al.sub.2O.sub.3 component, 20-50% of a GeO.sub.2 component and greater than 0% to 15% of a Bi.sub.2O.sub.3 component and/or a TeO.sub.2 component.

An optical glass contains: a P.sub.2O.sub.5 component of 30 to 60 mass % (exclusive of 30); an Al.sub.2O.sub.3 component of 2 to 10 mass % (exclusive of 2); a TiO.sub.2 component of 10 to 36 mass % (exclusive of 36); an Nb.sub.2O.sub.5 component of 0 to 5 mass %; a Ta.sub.2O.sub.5 component of 0 to 15 mass %; a Bi.sub.2O.sub.3 component of 0 to 5 mass % (exclusive of 5); and an Sb.sub.2O.sub.3 component of 0 to 1 mass %; and a BaO component of 1 to 20 mass %.

An optical glass contains: a P.sub.2O.sub.5 component of 30 to 60 mass % (exclusive of 30); an Al.sub.2O.sub.3 component of 2 to 10 mass % (exclusive of 2); a TiO.sub.2 component of 10 to 36 mass % (exclusive of 36); an Nb.sub.2O.sub.5 component of 0 to 5 mass %; a Ta.sub.2O.sub.5 component of 0 to 15 mass %; a Bi.sub.2O.sub.3 component of 0 to 5 mass % (exclusive of 5); and an Sb.sub.2O.sub.3 component of 0 to 1 mass %; and a BaO component of 1 to 20 mass %.

Glass compositions include phosphorus oxide (P.sub.2O.sub.5), niobia (Nb.sub.2O.sub.5), barium oxide (BaO) and potassium oxide (K.sub.2O) as essential components and may optionally include titania (TiO.sub.2), calcium oxide (CaO), sodium oxide (Na.sub.2O), lithium oxide (Li.sub.2O), bismuth oxide (Bi.sub.2O.sub.3), strontium oxide (SrO), tungsten oxide (WO.sub.3) and other components. The glasses may be characterized by high refractive index at 587.56 nm at comparably low density at room temperature.