Surface and Bulk Crystallization of Glass-Ceramic in the Na2O–CaO–ZnO–PbO–Fe2O3–Al2O3–SiO2 System Derived from a Goethite Waste

Abstract

A goethite waste from zinc hydrometallurgical processes has been used to produce a glass-ceramic in the Na2O–CaO–ZnO–PbO–Fe2O3–Al2O3–SiO2 system. The surface and bulk microstructure of this glass-ceramic have been studied by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The surface was comprised of crystalline and glassy areas. Two different types of crystalline growth and two morphologies were observed in the crystallized and glassy zones, respectively. The bulk microstructure was composed of a homogeneously distributed dendritic network comprised of small crystallites of magnetite. A glassy matrix was observed surrounding the magnetite network. Further heat treatment produced the precipitation of a non-stoechiometric zinc ferrite with magnetite crystals, being the nucleating agents of the secondary phase.