IntroductionGlass scintillators are commonly utilized for the detection of high-energy rays in various applications such as nuclear medicine imaging, industrial non-destructive testing, high-energy nuclear physics, safety inspection, and environmental monitoring. The scintillation glass with a high density is critical for improving the absorption and interception capabilities of rays and particles, thereby favoring the enhancement of the detector efficiency. This review represented recent development on high-density scintillation glass doped with rare-earth ions like Ce³⁺, Tb³⁺, and Eu³⁺. The critical parameters such as density, decay time, light output, and radiation resistance affecting the performance of the scintillation glass were discussed.Overall, the research delves into the scintillation mechanism of scintillation glass and presents an overview of the preparation process for high-density variants. The research progress on rare-earth ion-doped high-density scintillation glasses containing Ce³⁺, Tb³⁺, and Eu³⁺ ions was summarized, highlighting characteristics like density, light yield efficiency (LY), and decay time (τ). Some factors affecting these properties (i.e., substrate selection, energy transfer among ions, and reduction atmosphere) were also discussed.Ce³⁺-doped glass exhibits a nanosecond-level decay time. At the present, the density of Ce³⁺ doped scintillation glass can reach up to 6 g/cm³, but the light yield of this component is significantly low. The luminescence efficiency of the glass can be improved via introducing Gd₂O₃, which enhances the energy transfer between Gd³⁺ and Ce³⁺, while increasing the glass density. Also, incorporating fluoride into the oxide glass can lower the phonon energy, decrease the chances of non-radiative transition, and enhance the light yield. Ce³⁺ is prone to oxidation to non-luminescent Ce⁴⁺ during high-temperature melting. This oxidation process can be effectively controlled by using a reducing atmosphere (CO, H₂) or adding reducing agents such as Si₃N₄, SiC, AlN, etc.The density of Tb³⁺-doped scintillation glass can reach 7.15 g/cm³, with a decay time in the millisecond range. Enhancing the luminescence efficiency of Tb³⁺ is achievable through the energy transfer between Gd³⁺-Tb³⁺, Ce³⁺-Tb³⁺, Dy³⁺-Tb³⁺, while the introduction of fluoride and reducing agents can effectively boost the light yield. Eu³⁺-doped scintillation glass can achieve a density of 6.60 g/cm³, and the addition of Gd³⁺ and Tb³⁺ can effectively enhance the emission intensity of Eu³⁺ ions.High density scintillating glasses doped with other rare-earth ions, such as Pr³⁺, Dy³⁺, Sm³⁺, and Er³⁺, can achieve a high density and exhibit distinct scintillation properties because of their unique energy level structures. However, the light yield of these glasses is too low to be used in practical applications.Summary and ProspectsA high-density and high-yield scintillation glass is needed. Despite the efforts of scientific research personnel, producing flashing glass with both a high density and a high yield remains a challenge. The main reason is that in high-density glass, although the introduction of heavy metal ions increases the density of the glass, it may lead to an increase in non-radiative transition channels, hindering the transfer of energy from the substrate to the luminescent center. Also, an increase in density can enhance the absorption and scattering of light, thereby reducing the effective amount of excitation light reaching the luminescent center. In addition, high density glass matrix may cause the local environment around rare-earth ions to become complex, affecting their energy level structure. To prepare scintillation glass that can meet both high-density and high light yield, several aspects can be considered. Firstly, the use of a reducing atmosphere such as H₂ or CO and the addition of reducing agents like carbon powder can effectively control the valence of luminescent ions (i.e., Ce³⁺, Tb³⁺) during the melting process, preventing the formation of high valence ions. Using fluoride instead of partial oxides can reduce the melting point of the material and improve the light output via altering the band gap structure of the glass. The smaller volume of fluoride ions simultaneously contributes to the increased density of the glass. The utilization of energy transfer between ions can significantly enhance the light yield of glass. Some impurities and defects in glass can be minimized via utilizing high-purity raw materials and optimizing process steps such as melting and annealing. This can enhance the transparency and uniformity of the matrix, leading to a reduction in non-radiative transitions and an improvement in luminescence performance. It is possible to induce the formation of microcrystalline structures in glass via controlling the cooling rate or subsequent heat treatment. This optimization can enhance the energy transfer path, minimize scattering losses, and ultimately improve the luminescence efficiency.