Crystal Interface Control at Low Thermal Gradient and Investigation of the Effect of Cr on the Crystal Structure and Optical Properties of Bismuth Silicate

Abstract

Single crystals of bismuth silicate (Bi12SiO20) doped with chromium (0.05, 0.25, 0.5, and 1.0 at%) have been grown along ⟨110⟩ by Czochralski technique. The effect of growth parameters like low axial thermal gradient and crystal rotation rate on the crystal−melt interface is investigated by varying these parameters. Further, the effect of Cr incorporation on the lattice parameter, optical bandgap, emission characteristics, and refractive index is studied. It is observed that as the concentration of Cr increases, the lattice parameter increases, because the size of Cr ion is higher than that of Si ion which it replaces. The bandgap is found to decrease with the increase in the concentration of Cr in the lattice of Bi12SiO20. The estimated bandgap energy of all the samples lies between 2.16 and 3.12 eV. The estimated Urbach energy is ≈115 meV for undoped BSO and it is slightly higher (≈200 meV) for Cr‐doped crystals. Further, 0.05 and 0.25 at% Cr‐doped samples exhibit emission peak at around 470 nm on excitation at 420 nm. The refractive index is found to decrease with the increase in Cr concentration in the lattice.