Colorless, transparent SnO–P 2 O 5 (SP) glasses with 60–70 mol% SnO compositions were prepared by melting at 880–1000 °C in Ar atmosphere using commercial SnO and P 2 O 5 powders as raw materials and vitreous carbon crucibles. SP glasses are characterized by glass transition temperature, onset of crystallization, thermal expansion coefficient and weight loss after immersion test. The viscosity of 67SnO–33P 2 O 5 glass was measured by a penetration method in the range of 10 7.9 –10 10.5 Pa s at 267–290 °C. The results of optical properties show that the transparent SP glasses have high refractive indexes over 1.75 and high transmission over 80% in the visible and IR region of 380 and 2700 nm.
