Solid solubility and charge compensation/exchange mechanisms in Ga- or Mn-Doped CeO2 thin films on 3D printed biomedical titanium alloy

CeO2 films doped with 0–9 mol% Ga/Mn were fabricated by spin coating on 3D-printed Ti6Al4V, calcined at 650 °C for 2 h, and characterised by TEM, FESEM, 3D laser scanning confocal microscopy, GAXRD, and XPS. The results depend on the roles of several factors: (1) Sol-gel precursor viscosity affected pore filling and surface coverage. (2) Lattice contraction and resultant intervalence charge transfer increased the Ce3+ concentration as a minority effect. (3) Substitutional solid solubility and associated redox charge compensation controlled the defect equilibria, which highlight the majority role of this solid solubility mechanism in decreasing the Ce3+ concentration. (4) Electronegativity played a negligible role in affecting the valences but was important in initiating intervalence charge transfer. (5) Multivalence charge transfer combined electron exchanges between film matrix, dopants, and Ti substrate. The present work provides a foundation to interpret the effects of extrinsic effects from both dopant and substrate on the properties of films.