Zero photoelastic zinc tin phosphate glass without lead oxide.

The photoelastic constant (PEC) is evaluated for 15 zinc tin phosphate glasses in a series of xZnO-(67-x)SnO-33P(2)O(5) where x is 0-30 mol. % at 0.5-7 mol. % intervals. The phase retardation of polarized light, passing through a disk sample with applying various uniaxial loads, was measured for PEC determinations by using a frequency stabilized transverse Zeeman He-Ne laser as a polarized light source. The substitution of ZnO for SnO results in the increase of PEC from negative to positive values in the range of -1.43 and +1.45×10(-12) Pa(-1). The minimum PEC value of 0.04±0.02×10(-12) Pa(-1) was experimentally obtained in the 18.5 mol. % ZnO-48.5 mol. % SnO-33 mol. % P(2)O(5) glass.