Doping by diffusion and implantation of V, Cr, Mn and Fe ions in uncoloured beryl crystals

Colouration in a natural single crystal of uncoloured beryl was carried out using doping by diffusion and ion implantation with ion species of V, Cr, Mn or Fe. The experimental results obtained for the diffused samples using optical absorption, electron paramagnetic resonance and inductively coupled plasma-laser ablation-mass spectroscopy techniques revealed that these ions could be doped and diffused in the crystal. It was impossible to ascertain experimentally whether implanted ions were introduced into the samples because of a low dose used (2 x 1016 ions/cm2). It was found that two ions existent in the natural sample, that is, Mn2+ ions in octahedral coordination and Fe3+ ions in the structural channels characteristic of beryl, were converted into Mn3+ and Fe2+ ions, respectively, during the ion implantation process. In diffusion processes, Fe-diffused samples showed low activation energy and high diffusion coefficient than the other diffused samples. This is in accordance of a finding of Batra et al. that Fe3+ ions have the spherically symmetric coordination d5. Difference in the energy activation and diffusion coefficient was also found in samples diffused along and perpendicular to c-axis