Borosilicate glass compound for producing glass tubes and use of same for the production of glass tubes and as sleeve for lamps

摘要

Borosilicate glass comprises (in mole%, based on oxide) silicon dioxide (74-81), boron trioxide (8.5-14.5), aluminum oxide (0.5-3.5), sodium oxide (1.5-3.5), potassium oxide (1-2), lithium oxide (0-10), magnesium oxide (0.5-1.5), calcium oxide (0.5-1.5), barium oxide (0.0.6), titanium dioxide (2-3.5), zirconium dioxide (0-1), and refining agents containing antimony trioxide (0-0.15), cerium dioxide (0-0.5) and tin oxide (0-0.5). The molar ratio of sodium oxide and sum of sodium- and potassium oxide is greater than 0.4-= 0.72.