Structure and composition peculiarities and spectral-luminescent properties of colorless and pink Bi4Ge3O12 scintillation crystals

Abstract Czochralski-grown colorless and pink Bi 4 Ge 3 O 12 (BGO) single crystals have been characterized by the X-ray diffraction, X-ray absorption, and luminescence and optical spectroscopy. Additional high-temperature vacuum annealing of the as-grown colorless crystal at 900–950 °C using a special reducing agent leds to the appearance of pink coloration and modification of its properties. The refinement of actual compositions of both BGO crystals showed the distribution of the Bi 3+ ions over two, tetrahedral and octahedral, sites, the Bi content in the colorless crystal being greater and lower in the octahedral and tetrahedral sites, respectively, compared with the colored crystal. A small amount of Bi 5+ ions was revealed in the tetrahedral sites of the colorless crystal. Oxygen vacancies, as a part of the color center responsible for the crystal coloration, were found in the structure of pink sample. The pink BGO crystal is characterized by photoluminescence in the near infra-red spectral range.