XRD Line Profile Analysis for Calcite Produced by Precipitation Method at Different Pre-Cursor Concentration

Abstract

Abstract Calcium carbonate (CaCO3) nanocrystalline structural properties is rarely reported although it is critical for predictive behavior in a sensitive application. Calcite is the most thermodynamically stable phase, and its structures and lattice parameters are rarely reported. In this work, detailed structural studies were performed by X-ray diffraction line profile analysis. Single-phase crystalline calcite nanocrystals were synthesized by additives-free precipitation method to study the effect of different concentrations of precursors on the crystal structure. Titration was done for different concentrations (0.05-1.0) M of precursors at 25°C. The optimal titration technique at 25°C, 0.5M of precursor solution produced 85.71nm single-phase calcite in powder form. Analysis by X-ray diffraction confirmed that concentration limits at 0.5M, microstrain 5.34 x10-4 (lines-2/m4) produced the smallest single-phase calcite nanocrystals yet at 25°C by precipitation method. When concentration increases, distortion in the CaCO3 lattice occurs and the nucleation and growth decreases hence lattice constant decreases. The concentration limit is reached when the CaCO3 element is no more available to form hydrogen bonding for molecular recognition for CaCO3 crystalline and the formation of non-covalent bonding and interactions. Hence drastic bigger particles and agglomeration at concentrations above 0.5M. Agglomeration occurs due to attractive Van Der Waals forces from inadequate zeta potential for small particle suspension. It can be concluded that single-phase calcite nanocrystals were successfully synthesized by an additives-free precipitation method suitable for more sensitive applications like biosensor and medical devices.