Preparation and characterization of a novel luminescence nano-sillenite (Bi 12 SiO 20 ) glass ceramic within Bi 2 O 3 –ZnO–SiO 2 system

Bismuth silicate with sillenite structure (Bi 12 SiO 20 ) nanophase was prepared via melt–quenching technique in the Bi 2 O 3 –ZnO–SiO 2 glass system. The effect of replacement ZnO by Bi 2 O 3 was studied. Their thermal behavior showed the change of glass transition temperature (Tg) from 577 °C in the Bi 2 O 3 -free glass to 438 °C in ZnO-free glass. In addition, the crystallization temperatures were not only changed from two to one peak, but also decreased from 927 to 476 °C in the same order. According to the heat treatment regimes, willemite, sillenite, tetragonal Bi 2 O 3 , cubic Bi 2 O 3 and traces of ZnO were crystallized with different ratios depending on the change in composition and temperature. Sillenite was enhanced with increase heat treatment temperature and/or Bi 2 O 3 additions. Heat treatment at 650 °C/10 h revealed the best regime, where higher degree of crystallization was achieved. The microstructure at 700 ℃/30 min showed nano-scale oriented parallel rod crystals with hexagonal making at their end, whereas clusters of irregular nano-size crystals was appeared at 650 °C/10 h. Transmission spectra of the glasses in UV–Vis–midIR region were increased with Bi 2 O 3 addition reaching 74% in 100B. Photoluminescence properties of both glasses and their corresponding glass–ceramics showed luminescence nature since the blue and green colors were clearly appeared. Calculation of optical bandgap (E opt ) revealed 3.2–2.19 eV with increasing Bi 2 O 3 ; these values are located in the semiconducting range. The prepared samples can be utilized in electro-optical instruments, also the high transmission in mid-IR nominate it for IR transmitting windows.