Crystal growth, structure and thermal properties of anhydrous zinc carbonate (ZnCO3).

• High P-T method is proved to be the simplest for ZnCO 3 synthesis. • The crystal structure of impurity-free ZnCO3 was determined by single crystal X-ray diffraction. • Accurate thermal expansion of ZnCO 3 was quantified by single crystal X-ray diffraction at different temperatures. Carbonate materials have been increasingly favoured in terms of the development of flame retardants because of the eternal subject of inorganic carbon sequestration. In this regard, anhydrous zinc carbonate (ZnCO 3) has been deemed as suitable candidate thanks to its excellent flame retardancy compared to traditional hydroxid flame retardant. However, the single crystals growth, accurate characterizations of structural and thermal properties are still not entirely clear from previous studies. With this in mind, ZnCO 3 single crystals were synthesized under high-pressure-temperature conditions (high P-T; 3 GPa and 973 K). The crystal structure of impurity-free ZnCO 3 was determined by means of single crystal X-ray diffraction (XRD). The symmetry was identified as R 3 ¯ c , while the unit cell parameters were a= 4.6463(3) Å and c= 15.0015(11) Å with a final R value of 0.0229. The quantitative analyses of Raman spectrum and infrared absorption indicate that the as-synthesized ZnCO 3 is anhydrous phase. Using Thermogravimetric (TG) / Differential Scanning Calorimeter (DSC) measurements, ZnCO 3 was decomposed in the temperature range of 593–773 K, whereas the heat capacity and the endothermic peak were determined. According to the single crystal XRD from 150 K to 383 K, the thermal expansion coefficients were quantified as α a = 7.90 × 10−6 K−1 and α c = 22.8 × 10–6 K−1, as well as α Vunit cell = 38.8 × 10–6 K−1. These findings provide a precise characterisation and obtain important thermal parameters for the evaluation of its flame retardant properties. [ABSTRACT FROM AUTHOR]