The invention relates to a radiopaque glass having a refractive index n.sub.d of 1.480 to 1.561, this glass, apart from impurities at most, being free from SrO and PbO. The glass is based on the SiO.sub.2, Al.sub.2O.sub.3 and B.sub.2O.sub.3 system. The radiopacity can be adjusted using Cs.sub.2O in particular in combination with BaO and/or SnO.sub.2 optionally in conjunction with fluorine. The glass may be used in particular as dental glass or as optical glass.

The laminate of the present disclosure includes multiple glass ceramic layers each containing quartz and a glass that contains SiO.sub.2, B.sub.2O.sub.3, Al.sub.2O.sub.3, and M.sub.2O, where M is an alkali metal. The B concentration of a surface layer portion of the laminate is lower than the B concentration of an inner layer portion of the laminate.

ZrO.sub.2-toughened glass ceramics having high molar fractions of tetragonal ZrO.sub.2 and fracture toughness value of greater than 1.8 MPa.Math.m.sup.1/2. The glass ceramic may also include also contain other secondary phases, including lithium silicates, that may be beneficial for toughening or for strengthening through an ion exchange process. Additional second phases may also decrease the coefficient of thermal expansion of the glass ceramic. A method of making such glass ceramics is also provided.

ZrO.sub.2-toughened glass ceramics having high molar fractions of tetragonal ZrO.sub.2 and fracture toughness value of greater than 1.8 MPa.Math.m.sup.1/2. The glass ceramic may also include also contain other secondary phases, including lithium silicates, that may be beneficial for toughening or for strengthening through an ion exchange process. Additional second phases may also decrease the coefficient of thermal expansion of the glass ceramic. A method of making such glass ceramics is also provided.

The present disclosure provides a novel glass composition that has a low permittivity and is suitable for mass production. A glass composition provided satisfies, in wt %, for example, 40≤SiO.sub.2≤60, 25≤B.sub.2O.sub.3≤45, 0<Al.sub.2O.sub.3≤18, 0<R.sub.2O≤5, and 0≤RO≤12, and satisfies at least one of: i) SiO.sub.2+B.sub.2O.sub.3≥80 and SiO.sub.2+B.sub.2O.sub.3+Al.sub.2O.sub.3≤99.9; and ii) SiO.sub.2+B.sub.2O.sub.3≥78, SiO.sub.2+B.sub.2O.sub.3+Al.sub.2O.sub.3≤99.9, and 0<RO<10. Another glass composition provided includes SiO.sub.2, B.sub.2O.sub.3, Al.sub.2O.sub.3, R.sub.2O, and 3<RO<8 at the same contents as the above, and satisfies SiO.sub.2+B.sub.2O.sub.3≥75 and SiO.sub.2+B.sub.2O.sub.3+Al.sub.2O.sub.3<97, where R.sub.2O=Li.sub.2O+Na.sub.2O+K.sub.2O and RO=MgO+CaO+SrO.

The present disclosure provides a novel glass composition that has a low permittivity and is suitable for mass production. A glass composition provided satisfies, in wt %, for example, 40≤SiO.sub.2≤60, 25≤B.sub.2O.sub.3≤45, 0<Al.sub.2O.sub.3≤18, 0<R.sub.2O≤5, and 0≤RO≤12, and satisfies at least one of: i) SiO.sub.2+B.sub.2O.sub.3≥80 and SiO.sub.2+B.sub.2O.sub.3+Al.sub.2O.sub.3≤99.9; and ii) SiO.sub.2+B.sub.2O.sub.3≥78, SiO.sub.2+B.sub.2O.sub.3+Al.sub.2O.sub.3≤99.9, and 0<RO<10. Another glass composition provided includes SiO.sub.2, B.sub.2O.sub.3, Al.sub.2O.sub.3, R.sub.2O, and 3<RO<8 at the same contents as the above, and satisfies SiO.sub.2+B.sub.2O.sub.3≥75 and SiO.sub.2+B.sub.2O.sub.3+Al.sub.2O.sub.3<97, where R.sub.2O=Li.sub.2O+Na.sub.2O+K.sub.2O and RO=MgO+CaO+SrO.

A sealing glass is provided that includes SiO.sub.2, Al.sub.2O.sub.3 having a content of less than 2% by weight, is free of PbO except for unavoidable impurities, a coefficient of linear thermal expansion (∝.sub.20-300 of more than 10*10.sup.−6/K, a dielectric constant (ε.sub.r) in the range from at least 7.10 to not more than 7.80 at a measurement frequency of 1 MHz and a temperature of 25° C., and a glass transition temperature (T.sub.g) in a range from 400 to 550° C.

ZrO.sub.2-toughened glass ceramics having high molar fractions of tetragonal ZrO.sub.2 and fracture toughness value of greater than 1.8 MPa.Math.m.sup.1/2. The glass ceramic may also include also contain other secondary phases, including lithium silicates, that may be beneficial for toughening or for strengthening through an ion exchange process. Additional second phases may also decrease the coefficient of thermal expansion of the glass ceramic. A method of making such glass ceramics is also provided.

ZrO.sub.2-toughened glass ceramics having high molar fractions of tetragonal ZrO.sub.2 and fracture toughness value of greater than 1.8 MPa.Math.m.sup.1/2. The glass ceramic may also include also contain other secondary phases, including lithium silicates, that may be beneficial for toughening or for strengthening through an ion exchange process. Additional second phases may also decrease the coefficient of thermal expansion of the glass ceramic. A method of making such glass ceramics is also provided.

A glass substrate for high-frequency devices includes, in terms of molar percentage based on oxides: one or more alkaline-earth metal oxides in a total amount of 0.1 to 13%; Al.sub.2O.sub.3 and B.sub.2O.sub.3 in a total amount of 1 to 40%, in which a molar ratio of the contents represented by Al.sub.2O.sub.3/(Al.sub.2,O.sub.3+B.sub.2O.sub.3) is 0 to 0.45; at least one oxide selected from the group consisting of Sc.sub.2O.sub.3, TiO.sub.2, ZnO, Ga.sub.2O.sub.3, GeO.sub.2, Y.sub.2O.sub.3, ZrO.sub.2, Nb.sub.2O.sub.5, In.sub.2O.sub.3, TeO.sub.2, HfO.sub.2, Ta.sub.2O.sub.5, WO.sub.3, Bi.sub.2O.sub.3, La.sub.2O.sub.3, Gd.sub.2O.sub.3, Yb.sub.2O.sub.3, and Lu.sub.2O.sub.3, in a total amount of 0.1 to 1.0%; and SiO.sub.2 as a main component. The glass substrate has a dielectric dissipation factor at 35 GHz of 0.007 or less.