Three general systems, tetrahedrally coordinated oxides, apatite oxides and brownmillerite type Ba\(_2\)Sc\(_2\)O\(_5\) systems have been investigated. Powder diffraction indicated the successful incorporation of aluminium and gallium into Ba\(_2\)GeO\(_4\) which led to an increase in ionic conductivity, with a further increase of an order of magnitude in wet atmospheres due to proton conductivity. Neutron diffraction and TGA studies indicated the successful incorporation of water and flourine in La\(_8\)Sr\(_2\)(Si/Ge)\(_6\)O\(_2\)\(_6\) apatites. The interstitial positions for flourine and water ions were different from each other and for germanium and silicon apatites suggesting that the interstitial positions are composition dependant rather than universal for apatite systems. Neutron diffraction, TGA and AC impedance spectroscopy indicated successful doping of Y/Yb into BaSc\(_0\)\(_.\)\(_6\)\(_5\)\(_-\)\(_x\)Ti\(_0\)\(_.\)\(_3\)O\(_2\)\(_.\)\(_6\)\(_5\) stabilising the oxygen deficient perovskite structure with increased stability of CO\(_2\) and good conductivity. Whilst neutron diffraction of 4K on hydrated BaSc\(_0\)\(_.\)\(_2\)\(_5\)Y\(_0\)\(_.\)\(_4\)\(_5\)Ti\(_0\)\(_.\)\(_3\)O\(_2\)\(_.\)\(_6\)\(_5\) has located the proton positions.