Comparison of reidite formation between zircon bulk and nanoparticles

Although modifying high-pressure behavior through the particle-size of a material is well recognized, a clear mechanism, underlying the start and subsequent growth of a high-pressure phase, remains elusive. Here, we investigate the effects of particle-size on the formation of reidite (ZrSiO4, I41/a), a high-pressure phase of zircon (ZrSiO4, I41/amd), by comparing zircon nanoparticles with bulk. This is done by high pressure Raman scattering and synchrotron X-ray diffraction experiments on zircons pressurized in diamond anvil cells and subsequent transmission electron microscopy analysis of quenched samples. As compared to bulk, the larger surface energy of nanoparticles is the cause of a higher critical pressure required to start the transition to reidite. However, after passing the critical pressures, the similar growth trends between nanoparticles and bulk indicate that the reidite growth is dependent on the core, rather than the surface. These results are important to identify craters caused by meteorite impacts using reidite as a high-pressure indicator, as nanoparticles are formed in naturally-occurring, highly radiation-damaged zircon.