  Solution precursor thermal spray can become a breakthrough technology for the
deposition of coatings with novel chemistries; however, the understanding of
the process that the feedstock material undergoes is still poorly understood
when compared to more traditional presentations (i.e. powder and suspension).
In this paper, niobium-doped TiO2 coatings were deposited by solution precursor
high velocity oxy-fuel spraying, studying its microstructure and phase. It was
reported that a lower flame temperature produced a highly porous coating, while
the porosity was reduced at higher flame temperature. Investigation of the
phase content showed that, contrary to our current understanding, a higher
flame power implied an increase of the anatase phase content for solution
precursor spray. Three methods were used: Rietveld refinement, peak height and
peak area of the x-ray diffraction patterns. Additionally, single splats were
analysed, showing that as the precursor travels through the flame, pyrolysis
and sintering takes place to form the solid material. These results were used
to derive a model of the physico-chemical transformation of the solution
precursor. This work proves that solution precursor thermal spray is a
promising technique for the deposition of doped ceramic coatings, being the
microstructure and phase content controllable through the spraying parameters
