Determination of Quartz in Inorganic Mixtures by TGA/DSC and DSC

In the building materials industry, inorganic mixtures (natural products) are often used whose exact composition can vary but must nevertheless be known for further processing. In this article, we show how the quartz content of inorganic mixtures can be quickly and easily determined by TGA/DSC and DSC.

Introduction

Quartz is a crystalline mineral and consists of SiO₂. It is used as an additive in the manufacture of porcelain, as a filling material in various products, as a gemstone, or for the manufacture of glass [1]. TGA/DSC instruments can be used to analyze the quartz content of inorganic powders (for example mixtures of talc and quartz). Quartz exists in different modifications. When quartz is heated, dif ferent solid–solid transitions occur. The reversible phase change from α-quartz to β-quartz that occurs at about 570 °C is very useful for detecting quartz in materials. On a DSC curve, the phase change is observed as an endothermic or exothermic peak (on heating or cooling). If inorganic samples undergo decomposition in this temperature range, they should first be heated to 1000 °C and the quartz transition evaluated on cooling. Otherwise, the quartz transition is overlapped by other effects and cannot be evaluated. To quantify the quartz content, it is necessary to measure a reference material consisting of the same type of quartz used as the additive.

_{Determination of quartz in inorganic mixtures | Thermal Analysis Application No. UC 593 | Application published in METTLER TOLEDO Thermal Analysis UserCom 59}