Micro-crystals of bismuth orthosilicate (Bi₄Si₃O₁₂) were synthesized by a sol–gel method, using stoichiometric Si(OC₂H₅)₄, Bi(NO₃)₃·5H₂O as the precursors and acetic acid as the solvent. The calcining process of the as-dried gel was studied by total gravity/differential scanning calory (TG/DSC), X-ray diffraction (XRD) and infrared (IR) spectra. Experiments showed that single phase of Bi₄Si₃O₁₂ could be obtained by sol–gel method at a calcining temperature of 900 °C. Phase separation in the sol–gel process was found during the calcination.

Phase relation of Bi₂O₃SiO₂ system was evaluated experimentally from DTA and XRD measurements and its stable and metastable phase diagrams were proposed. Although BSO melts near-congruently at 1025°C in the stable phase equilibrium, its melt crystallizes to form metastable phase Bi₂SiO₅ in accordance with the metastable phase diagram while cooling. Therefore, BSO couldn't nucleate and crystallize spontaneously without crystal seed and only Bi₂SiO₅ crystallized at about 850°C with significant supercooling during Bridgman growth. BSO single crystal with 20×20×100mm³ was grown in a vertical Bridgman furnace with a BSO seed according to its phase diagram. The measuring results of scintillation properties of BSO specimen show that its decay constant is 91 ns (about 1/3 of BGO) and light output is 23% of BGO.

Colorless and crack-free single crystals of bismuth silicate (Bi₄Si₃O₁₂, BSO) scintillators have been grown by the vertical Bridgman method. Some segregation phases have been found to form on the surface and at the top of the crystals grown from both stoichiometric and off-stoichiometric melt compositions. The excitation and emission spectra are similar to BGO. The light output is 20% of BGO, giving energy resolution of 32% for 662 keV γ-rays (¹³⁷Cs). The decay constants are 2.4 ns (for 6% of intensity), 26 ns (12%) and 99 ns (82%). The radiation hardness against⁶⁰Co γ-rays was found about 10⁵–10⁶ rad at the emission peak of 480 nm for undoped and it was almost negligible up to 10⁷ rad for 0.2 at.% Ce doped crystals. We have also achieved a considerable improvement in the growth of large size crystals, offering the possible application in γ-ray detectors at high energies. Clear blocks with transverse/longitudinal dimensions as large as 25 mm/200 mm were produced with good reproducibility. The pulse height uniformity along the longitudinal axis is within ±2%. The scintillation characteristics are similar to those of small crystals.

Bi₂O₃–SiO₂–Al₂O₃ based glasses of good transparency with high Bi₂O₃ content (~ 36 mol%) have been obtained by using melting method. Glass transition, crystallization and phase reaction temperatures of as-synthesized glass have been characterized by differential scanning calorimetry (DSC). The X-ray diffraction (XRD) analysis confirms the amorphous structure of the glass samples before and after the annealing. Ultraviolet and visible transmittance spectra show that the transmittance of as-synthesized glasses (0.6 mm thickness) can reach up to 80.1% in the visible region (above 550 nm), with the cutoff wavelength at 386 nm. The linear absorption coefficient (α), optical mobility gap (E_opt) as well as Urbach energy (ΔE) are calculated from optical transmittance. After annealing at 550 °C, the transmittance increases slightly near the absorption edge which shifts itself towards shorter wavelength. The roles of composition, heating and annealing profile on the transmittance of glasses have been discussed. For Bi₂O₃–SiO₂–Al₂O₃ glasses with high Bi₂O₃ content, the Hruby factor is about 0.26, suggesting good stability.

Bismuth ortho-germanate (BGO) and bismuth ortho-silicate (BSO) crystals are described within an atomic cluster model. Electronic ground and first excited state for both crystal structures are calculated through unrestricted Hartree–Fock and configuration interaction methods, where the associated cluster geometries are optimized. The theoretical transition energies corresponding to the absorption and emission processes are very revealing. The displacement of one of the oxygen ions away from the bismuth in the excited state, together with the distributed spin density clearly shows that the excitation process cannot be understood as a deformed bismuth ion excitation. Instead, a molecular-like excitation is proposed.

A performance test has been made for an electro-magnetic calorimeter prototype comprised four identical BSO crystals arranged in a 2×2 matrix by utilizing a positron beam in the energy range from 100 to 800 MeV. The size of each crystal is 40×40×210 mm³. This is the world's largest BSO single crystal ever used as a photon detector. The obtained energy resolution is$({\sigma }_E/E{)}^2=((1.71\%\pm 0.03\%)/\sqrt{E}{)}^2+(1.12\%\pm 0.08\%{)}^2$ at room temperature, whereE is the incident positron energy given in GeV. A BGO calorimeter having the same geometry has been employed in the performance test for comparison. The basic scintillation characteristics of BSO crystals measured without the beam are also presented.

A beam test has been performed on a prototype electromagnetic calorimeter of bismuth silicate BSO crystals for the first time using electrons of 0.5–3.0 GeV. The calorimeter consists of nine BSO crystals,$22\mathrm{mm}\times 22\mathrm{mm}\times 180\mathrm{mm}$ (15.6 radiation lengths), arranged in a3×3$3\times 3$ array. Each crystal is coupled to a small photomultiplier tube of 20 mm in diameter. The obtained energy resolution is${\sigma }_E/E=(0.023\pm 0.003)/\sqrt{E(\mathrm{GeV})}\oplus (0.017\pm 0.002)$ for incident electrons of the energyE in GeV. The position information for an electron injected onto the center crystal of the calorimeter array is given with energy deposit signals from nine BSO crystals. The RMS position resolutionσ_x${\sigma }_x$ is parameterized as${\sigma }_x=[(3.2\pm 0.1)/\sqrt{E(\mathrm{GeV})}\oplus (1.3\pm 0.1)]\mathrm{mm}$ at the center of the crystal. Misidentification probability of pions to electrons is found to be∼10^-3$\sim {10}^{-3}$ for the pion momentum ranging from 1.0 to 3.0 GeV/c.