Microwave-compatible nepheline glass-ceramics

Claim 2

A glass-ceramic body in which the primary crystal phase is composed of nepheline crystals less than 20 microns in diameter, the body has a microwave compatibility value of less than 150° C., and the composition of the body, in percent by weight as calculated on an oxide basis, consists essentially of 30-55% SiO 2 , 28-38% Al 2 O 3 , 5-12% TiO 2 as a nucleating agent, and 10-20% R 2 O (Na 2 O+K 2 O+Li 2 O), each mole of R 2 O being composed of 0.65-0.95 moles Na 2 O, 0.05-0.15 moles Li 2 O and 0-0.20 moles K 2 O.

Claim 3

A glass-ceramic body in accordance with claim 1 wherein the body has a microwave compatibility of less than 100° C. and each mole of R 2 O contains 0.65-0.90 moles Na 2 O and 0.10-0.15 moles Li 2 O.

Claim 4

A glass-ceramic body in which the primary crystal phase is composed of nepheline crystals less than 20 microns in diameter, the body has a microwave compatibility value of less than 150° C., and the composition of the body, is percent by weight as calculated on an oxide basis, consists essentially of 30-55% SiO 2 , 28-38% Al 2 O 3 , 5-12% TiO 2 as a nucleating agent, and 10-20% R 2 O (Na 2 O+K 2 O+Li 2 O), each mole of R 2 O being composed of 0.65-0.95 moles Na 2 O, up to 0.20 moles K 2 O and up to 0.15 moles Li 2 O, both K 2 O and Li 2 O being present and the total content being at least 0.05 moles.

Claim 5

A glass-ceramic body in which the primary crystal phase is composed of nepheline crystals less than 20 microns in diameter, the body has a microwave compatibility value of less than 150° C., and the composition of the body, is percent by weight as calculated on an oxide basis, consists essentially of 30-55% SiO 2 , 28-38% Al 2 O 3 , 5-12% TiO 2 as a nucleating agent, and 10-20% R 2 O (Na 2 O+K 2 O+Li 2 O), each mole of R 2 O being composed of 0.65-0.95 moles Na 2 O, up to 0.20 moles K 2 O and up to 0.15 moles Li 2 O, both K 2 O and Li 2 O being present and the total content being at least 0.05 moles.

Claim 6

A glass-ceramic body in accordance with claim 3 wherein the body has a microwave compatibility of less than 100° C. and each mole of R 2 O contains 0.65-0.90 moles Na 2 O and both K 2 O and Li 2 O, the total content being at least 0.10 moles.

Claim 7

A glass-ceramic body in which the primary crystal phase is composed of nepheline crystals and there is a secondary celsian-type crystal phase with the crystals being not over 20 microns in diameter, the body has a microwave compatibility value below 100° C., has a thermal expansion coefficient of 80-95×10 -7 /° C., and the composition of the body, in percent by weight as calculated on an oxide basis, consists essentially of 30-55% SiO 2 , 28-38% Al 2 O 3 , 5-12% TiO 2 as a nucleating agent, 1-10% BaO, 0-3% K 2 O, 0-1 1/2% Li 2 O, 10-18% Na 2 O, 10-30% R 2 O (Na 2 O+K 2 O+Li 2 O)+BaO, each mole of R 2 O+BaO being composed of 0.50-0.80 moles Na 2 O, 0-0.15 moles Li 2 O, 0-0.20 moles K 2 O, the total Li 2 O+K 2 O being at least 0.10 moles, and 0.02-0.20 moles BaO.

Claim 8

A glass-ceramic body in which the primary crystal phase is composed of nepheline crystals and there is a secondary celsian-type crystal phase with the crystals being not over 20 microns in diameter, the body has a microwave compatibility value below 100° C., has a thermal expansion coefficient of 80-95×10 -7 /° C., and the composition of the body, in percent by weight as calculated on an oxide basis, consists essentially of 30-55% SiO 2 , 28-38% Al 2 O 3 , 5-12% TiO 2 as a nucleating agent, 1-10% BaO, 0-3% K 2 O, 0-1 1/2% Li 2 O, 10-18% Na 2 O, 10-30% R 2 O (Na 2 O+K 2 O+Li 2 O)+BaO, each mole of R 2 O+BaO being composed of 0.50-0.80 moles Na 2 O, 0-0.15 moles Li 2 O, 0-0.20 moles K 2 O, the total Li 2 O+K 2 O being at least 0.10 moles, and 0.02-0.20 moles BaO.

Claim 9

A glass-ceramic body in accordance with claim 5 wherein the TiO 2 content is 5-7%.

Claim 10

A glass-ceramic body in accordance with claim 5 wherein the composition contains up to 5% CaO.

Claim 11

A glass-ceramic body in accordance with claim 5 wherein each mole of R 2 O+BaO contains at least 0.05 moles each of Li 2 O and K 2 O.

Claim 12

A glass-ceramic body in accordance with claim 8 wherein each mole of R 2 O+BaO contains at least 0.10 moles BaO.

Claim 13

A glass-ceramic body in accordance with claim 5 wherein the moles of Al 2 O 3 exceed unity with SiO 2 in the range of 2.4 to 2.7 moles.

Claim 14

A glass-ceramic body in accordance with claim 10 wherein the molar composition, exclusive of nucleant and fining agent, is 2.4-2.6 moles SiO 2 , 1.03-1.15 moles Al 2 O 3 , 0.65-0.73 moles Na 2 O, 0.13-0.20 moles BaO, 0.05-0.08 moles Li 2 O, and 0.06-0.10 moles K 2 O.