The synthesis and spectroscopy of doped zircon and other lattices

The purpose of this project was to study the nature of two important ceramic pigments, vanadium-doped ZrSiO4 (zircon) which is blue and praesodymium-doped ZrSiO4 which is yellow. The investigation involved the synthesis of the pigments as powders as well as single crystals, and the study of the defect structure of the lattice sites using model potentials, the preferred doping sites by X-ray diffractrometry, the vibrational structure by Raman, resonance Raman and f.t.i.r. spectroscopy, and the electronic structures by e.s.r. spectroscopy. The solid-state syntheses of a series of host materials (ZrSiO4, HfSiO4, ZrGeO4 and HfGeO4) and the procedures appropriate to the inclusion of dopant ions V4+, Cr3+, Pr4+ and Tb4+ were examined. The effects of the various components on the synthesis of the host materials was determined and a mechanism for vanadium doping into ZrSiO4 was suggested. Single crystals of ZrSiO4 doped with V4+, Cr3+, Pr4+ or Tb4+, HfSiO4 doped with , ZrGeO4 doped with V4+ and Tb4+ and HfGeO4 doped with were grown using the flux growth technique. New fluxes were derived to grow better quality crystals of ZrGeO4 and enable the doping levels in ZrGeO4 and ZrSiO4 to be controlled. The composition of all the crystals grown was analysed by electron probe analysis. The defect energies for vanadium substitution into Zr4+ and Si4+ sites in ZrSiO4 were calculated using the CASCADE computer code and potential models for the Zr-O, Si-O, O-O, and V-O interactions. The doping sites for V4+ doped into ZrSiO4 ZrGeO4 as well as Tb4+ doped into ZrGeO4 were examined by single crystal X-ray diffraction. It was found that vanadium doped into both Zr4+ and Si4+ sites in ZrSiO4, into the Ge4+ site in ZrGeO4 and that Tb4+ dopes into the Zr4+ site in ZrGeO4. The vibrational structure of ZrSiO4 doped with different levels of V4+ was investigated by Raman and f.t.i.r. spectroscopy. The electronic structure of V4+ doped into ZrGeO4 and HfGeO4 was examined using e.s.r. spectroscopy