Lead-free, tin phosphate glasses contain 25-50 mole percent P.sub.2 O.sub.5, 30-70% SnO, 0-15% ZnO, the mole ratio of SnO:ZnO being greater than 5:1, and an effective amount up to 25% total of at least one oxide in the indicated proportion selected from the group consisting of up to 25% R.sub.2 O, wherein R.sub.2 O consists of 0-25% Li.sub.2 O, 0-25% Na.sub.2 O, and 0-25% K.sub.2 O, up to 20% B.sub.2 O.sub.3, up to 5% Al.sub.2 O.sub.3, up to 5% SiO.sub.2, and up to 5% WO.sub.3. The glasses are particularly useful as sealing glass frits in sealing material to join component parts in electrical and electronic devices. The sealing glass material may contain mill additions to reduce the effective coefficient of thermal expansion in a seal, as well as a strength reinforcing additive having a coefficient of thermal expansion preferably below 120.times.10.sup.-7 /.degree.C.