ZnO–PbO–B2O3 glassesas gamma-ray shielding materials Harvinder Singh a, Kulwant Singh a, Leif Gerward b, * , Kanwarjit Singh c, Hari Singh Sahota d , Rohila Nathuram e a Department of Physics, Guru Nanak Dev University, Amritsar-143005, Punjab, India b Department of Physics, Technical University of Denmark, Building 307, DK-2800 Kgs. Lyngby, Denmark c Department of Applied Physics, Guru Nanak Dev