Elastic Modulus and Fracture Toughness of Ternary PbO‐ZnO‐B 2 O 3 Glasses

The elastic moduli and fracture toughnesses of a series of PbO‐ZnO‐B 2 O 3 glasses were measured for different PbO/ZnO ratios and for B 2 O 3 contents from 30 to 70 mol%. Substituting ZnO for PbO increased both the elastic modulus and fracture toughness at all B 2 O 3 levels with the fracture toughness being related to the elastic modulus. Structural effects on these properties are discussed.