As a kind of high-energy electromagnetic radiation, gamma rays can lead to radiation effect and environmental pollution. To ensure the reliability and safety utilization of gamma radiations in different areas, materials with reliable gamma shielding performances should be developed. The existing efforts are to use glasses as alternative for the conventional radiation shielding materials. As a typical window material, glass itself has attracted wide attention due to its unique chemical and physical advantages. Among them, lead-based radiation shielding materials are widely used in the field of ionizing radiation protection due to their reliable physical properties. In the nuclear industry and high energy physics laboratories, different materials can be used for temporary or permanent shielding. The lead-based glass doped with heavy metal oxide PbO is widely used in the field of radiation shielding for a long time with reliable light transmission properties, which facilitates the observation and monitoring of radiation areas. In this paper, three kinds of transparent silicate glass with different PbO contents were prepared by a high-temperature melting forming method. The gamma-rays protection abilities of the three kinds of glass were investigated through experimental and thermotical methods. The chemical and thermal stability of the glass were also analyzed. In addition, the influence mechanism of the structure and performance differences of the three kinds of glass was also discussed.

Analytical pure quartz sand (SiO₂, purity 99.5%, in mass, the same below), lead monoxide (PbO, purity 99.0%), potassium nitrate (KNO₃, purity 99.0%) and sodium nitrate (NaNO₃, purity 99.0%) were selected as raw materials for preparation of three kinds of gamma-rays shielding glass materials by a high-temperature melting method. An appropriate amount of raw materials was thoroughly mixed and added to 3 L quartz crucible and heated in air at 1 200 ℃. Then the raw materials were melted at 1 250 ℃ for 14 h. The uniform melt was quickly poured into the 150 mm×150 mm×50 mm stainless steel mold preheated at 750 ℃. Finally, the quenched glasses were annealed at 450 ℃ for 12 h and cooled naturally to room temperature.

The density of the three glass samples was tested based on the Archimedes principle. The thermal expansion coefficient of glass samples was measured by a model Netzsch DIL 402 expansion coefficient tester. The infrared spectra were measured by a model Perkinelmer Spectrum 100 FTIR Spectrometer. The Raman spectra were tested by a model HORIBA LabRAM HR800 high-resolution Raman spectrometer. The gamma ray shielding test was completed in China Academy of Engineering Physics. The chemical stability test was completed in Chengdu Guangming Glass Co., LTD. The acid stability and moisture stability of the glass samples were tested according to the national standards GB/T 7962.14-2010 and GB/T 7962.15-2010, respectively. The thermal stability of the galss was also determined.

Glass structure becomes more compact with the exchange of Pb alternatives of Si, K and Na. Increasing the density of glass is conducive to improving its shielding performance, but this leads to significant changes in the optical properties, thermal properties and chemical stability of glass due to the increase of heavy metal content. The preparation of high transmittance glass is more difficult. The coefficient of thermal expansion of glass samples gradually decreases from 103.6 × 10^-7 ℃^-1 to 89.2 ×10^-7 ℃^-1, and the values of T_g and T_f also decrease with the increase of mass fraction of PbO in glass components. The change of the thermal properties of the three glass samples is a result of the joint action of PbO, Na₂O and K₂O. The FTIR spectra show that the added PbO is transformed into [PbO₄] units with 4 coordination numbers into the network under the condition of sufficient free oxygen as PbO content in the glass increases. These [PbO₄] units participate in the formation of silicate networks. The Raman spectra indicate that the silicate network structure is de-polymerized as PbO content is increased, and the enhancement of the characteristic vibrational peaks corresponding to the Pb-Si-O indicates an increase in the degree of participation of the [PbO₄] units in the formation of silicate network. The ion packing density of the glass sample gradually increases with the increase of PbO content, which shows that the compressible free volume per unit volume of the glass sample becomes smaller. PbO with a high concentration (x = 0.50 and x = 0.66) is used as a glass-forming agent, and the [PbO₄] structural units can form a connection structure with the silicon oxide tetrahedron, which plays a role in repairing the glass network.

The permeability of the glass can be improved via strictly controlling the iron content of the introduced raw materials and making full use of the double alkali effect of the glass. The actual shielding performance of glass is not a result of simple addition of various components. This can be affected by the actual composition content of the glass, melting process and endoplasmic uniformity. The influence of glass expansion coefficient on the thermal stability is much greater than that on its chemical stability.

PbO with a high concentration (x = 0.50 and x = 0.66) was used as a glass-forming agent, and the [PbO₄] structural units could form a connection structure with the silicon oxide tetrahedron, playing a role in repairing the glass network. The measured shielding rate of ⁶⁰Co gamma-ray could be 50% and the glass with 50% PbO content (in mass fraction) exhibited a linear transmission rate of more than 85% in the range of 400-800 nm. In addition, the reliable thermal and chemical stabilities were also reflected in the glass.