KINETIC DISSOCIATION OF NICKEL TITANATE AND NICKEL TUNGSTATE IN OXYGEN POTENTIAL GRADIENTS

Nickel titanate (NiTiO3) and nickel tungstate (NiWO4) were exposed to oxygen potential gradients at 1400 and 1100-degrees-C, and they were f ound to dissociate into their constituent oxides, namely, NiO and TiO2 , and WO3 and NiO, respectively. This is consistent with the non-equil ibrium phenomenon of kinetic decomposition. In the case of nickel tita nate, at the low-oxygen-potential side, TiO2 was formed as sharp needl e-like structures within the titanate matrix, while at the high-oxygen -potential side, NiO was formed. In contrast, NiO was formed at the lo wer-oxygen-potential side in the case of nickel tungstate, while WO3 v olatized off from the high-oxygen-potential side. This indicated that W diffuses faster than Ni in tungstates. In both cases, there were sig nificant macroscopic shifts of the oxide with respect to the original position, established with Pt markers, towards the high-oxygen-potenti al side.