title: Nanocrystallization in Oxyfluoride Glasses Controlled by Amorphous Phase Separation.
abstract: Transparent bulk glass-ceramics containing ZnF2, K2SiF6, and KZnF3 nanocrystals are successfully obtained from xKF-xZnF2-(100 - 2x)SiO2 oxyfluoride glasses for the first time to the best of our knowledge. The glass transition temperatures of heat-treated samples increase with time and approach values that resemble the temperatures chosen for thermal treatment. During nucleation and crystal growth, the residual glass around the crystals is depleted in fluoride which as glass component usually leads to a decrease in viscosity. The crystallization behavior notably depends on the glass composition and changes within a small range from x = 20 to 22.5 mol %. The occurrence of liquid/liquid phase separation in dependence of the composition is responsible for the physicochemical changes. Two different microstructures of droplet and interpenetrating phase separation and their compositional evolution are observed by replica transmission electron microscopy technique in the multicomponent glassy system. This study suggests that the size and crystal phase of precipitated crystallites can be controlled by the initial phase separation.
authors: Otto-Schott-Institut für Materialforschung, Jena University , Fraunhoferstraβe 6, 07743 Jena, Germany.|Laboratory of Infrared Materials and Devices, Research Institute of Advanced Technology, Ningbo University , Ningbo 315211, China.
authors: Changgui
authors: C
authors: Lin
authors: Otto-Schott-Institut für Materialforschung, Jena University , Fraunhoferstraβe 6, 07743 Jena, Germany.
authors: Christian
authors: C
authors: Bocker
authors: Otto-Schott-Institut für Materialforschung, Jena University , Fraunhoferstraβe 6, 07743 Jena, Germany.
authors: Christian
authors: C
authors: Rüssel
keywords: K2SiF6; KZnF3; Nanocrystallization; glass-ceramic; oxyfluoride glass; phase separation