Sol-Gel-Syntheses and Structural as well as Electrical Characterizations of Anatase- and Rutile-Type Solid Solutions...

This paper describes solid solutions in the quasibinary oxide system iridium-titanium IrO₂ -TiO₂ with rutile and anatase crystal structures. Based on X-ray diffraction evaluations using Rietveld refinements, changes of lattice parameters were determined within the composition series of 0-100 mol % iridium. These changes prove the existence of a complete solid solution series in the rutile structure type. The solubility limit for iridium in the anatase lattice was found to be 6.0(8) mol % iridium for the underlying sol-gel process. In addition, iridium is a promoter for the conversion from anatase to rutile type. Furthermore, the X-ray diffraction results of a calcination temperature series for the composition with 5 mol % iridium are shown, which confirm the findings of the composition series and allow conclusions on the phase segregation behavior. The results are complemented by 2-point conductivity measurements at different pressures in a piston press to investigate the question of the conductivity mechanism.