Band-gap correlations in Bi4Ge3O12 amorphous and glass–ceramic materials

Bonding Scheme and Optical Properties in BiM2O2(PO4) (M=Cd, Mg, Zn); Experimental and Theoretical Analysis

“…Based on this observation, the ratios between the excitation and band gap energies for M=Mg, Zn, and Cd read E ex / E g =4.68/3.75, 4.56/3.2, and 4.05/2.5 eV, respectively). This behavior was also observed for other compounds with Bi 3+ ions in literature, for example, Bi 4 Ge 3 O 12 , Bi 2 Al 4 O 9 , or a previous report on BiMg 2 PO 6 ( E ex / E g =4.54/3.6, 4.28/3.65, 4.51/3.58 eV, respectively). We recently suggested reasons for this odd behavior also observed in Sillen series: the lowest excited level 3 P 0 of Bi 3+ does not allow radiative emission and the shift of excited states with respect to the ground state along the M‐L axis in a configurational coordinate space accentuates this phenomenon.…”

Structural changes during the crystallization of the Bi4Ge3O12 glasses

“…3, curve c). Transmission electron microscopy (TEM) and the corresponding Selected Area Electron Diffraction (SAED) on glass ceramic annealed at 560°C have confirmed the presence of a uniform distribution of BGO nano-crystallites [19]. The XRD patterns have shown a substantial increase of the BGO crystalline fraction in the devitrified glass compared to the glass ceramic, and the mean size of the nano-crystals remains the same (about 50 nm).…”

Investigations of the non-isothermal crystallization of Bi4Ge3O12 (2:3) glasses

“…(10) and (11) with χ e = 0.1 (as resulted from XRD measurements), S = 4·10 − 4 μm − 2 and d 0 = 0.02 μm. The number of nuclei per unit volume, N 0 , is given by the ratio between the volume fraction of the crystalline phase and the maximum volume of crystallites which yields at N 0 = 3.56·10 4 μm − 3 .…”

“…The red-brown color of the obtained samples, due to the turbidity effects of the light scattering processes (Mie or Rayleigh) on the BGO clusters [10], leading to one broad peak centered at 500 nm. After the annealing at 833 K for 200 min with 10 K/min, the sample become transparent (is reduced with 20%) and the broad peak disappears, suggesting the rearranging of GeO 4 tetrahedra.…”