Er³⁺ and Yb³⁺ doped BaTiO₃ powders and films prepared by sol-gel method

In this work, BaTiO₃:Er³⁺ (0.5 and 5 mol%) and BaTiO₃:Yb³⁺ (0.05 and 6 mol%) powders and films were prepared by the sol-gel method. The powders and films were characterized by means of FT-IR, XRD, Raman, SEM, and UV analyses. The evolution from xerogel to a BaTiO₃ crystalline structure was monitored by FT-IR and XRD analyses. At 700 °C, the BaTiO₃:Er³⁺ and BaTiO₃:Yb³⁺ powders and films, synthesized by the sol-gel method in the presence or absence of PVP, crystallized in the cubic phase. The formation process of BaTiO₃ under different synthesis conditions is discussed, based on the XRD, FT-IR, and Raman results. BaTiO₃:Er³⁺ and BaTiO₃:Yb³⁺ films were elaborated using the dip-coating technique. The thin films presented a good homogeneity. An optimal concentration of polyvinylpyrrolidone (PVP) allows to yield the BaTiO₃ films with high thickness. PVP, which was used during the deposition to prepare BaTiO₃ films, changes the rheological properties of “sol” PVP which significantly reduced the deposition steps and avoided film cracking. The powder’s morphology is characterized by particle agglomeration, with a faceted and irregular shape.