Effects of pH value on growth morphology of LaPO₄ nanocrystals: investigated from experiment and theoretical calculations

The morphologies of the materials have strong effects on their performance in particular applications. In our experiment, we synthesized LaPO₄ successfully by the typical hydrothermal method in acidic conditions. The morphologies, preferred orientation and crystal facets are characterized by scanning electron microscopy, selected-area electron diffraction and high-resolution transmission electron microscopy. Combining the experimental findings, the surface energies of two major surfaces, (110) and (031) planes, were calculated using density functional theory methods. The theoretical calculations on the slabs surface energies were performed to simulate the shape of nanoparticles by the Wulff construction. The experimental results indicate that LaPO₄ prepared in this work shows rodlike structure. The equilibrium shape of clava with large length-diameter ratio is achieved. With increasing hydrogen ion concentration in solutions, the morphologies present as sticks and their length-diameter ratios tend bigger, which is consistent with experimental results to a great extent. (orig.)