Structural Study on PbO–SiO ₂ Glasses by X‐Ray and Neutron Diffraction and ²⁹ Si MAS NMR Measurements

Abstract

Structure of x PbO–(100− x )SiO 2 ( x =25–89) glasses has been investigated by means of the X‐ray and neutron diffraction and 29 Si MAS NMR measurements. In the radial distribution functions of all the glasses, the Pb–O correlation was observed at 0.23 nm, indicating that the PbO 3 trigonal pyramids units do exist in the whole glass forming composition range. Furthermore the existence of the first Pb–Pb correlation at ∼0.385 nm in the whole composition range suggests that the basic structural unit is considered to be a Pb 2 O 4 unit, which consists of the edge‐shared PbO 3 trigonal pyramids. These results strongly imply that the Pb 2 O 4 units participate in the glass network constructed by SiO 4 tetrahedra even at low PbO content. Differing from other lead‐containing glass systems, these structural characteristics of Pb ions in the PbO–SiO 2 glass system are responsible for the extremely wide glass‐forming region.