Upconversion Luminescence in Barium Titanate Xerogel Doped with Erbium and Ytterbium in Porous Anodic Aluminum Oxide

In this work, sol-gel synthesis and luminescence properties of erbium and ytterbium doped BaTiO3 (BaTiO3:Er,Yb) in porous anodic alumina are reported. Porous anodic alumina with its well-known tailor-made honeycomb structure was chosen as a template for the sol-gel synthesis of BaTiO3:Er,Yb. Porous anodic alumina was fabricated either on silicon wafer or aluminum foil. The sol corresponding to xerogel content of Ba0,76Er0,04Yb0,20TiO3 was deposited on porous anodic alumina by spinning, which was followed by drying and heat treatment at a relatively low temperature 450 °C on aluminum foil or 800 °C on silicon. Porous anodic alumina known also as an optically anisotropic structure differed in the experiments by diameter of the pores and thickness. Evidently, all fabricated samples demonstrated a roomtemperature erbium upconversion luminescence under excitation in the continuous-wave (CW) mode with a focused 980 nm laser beam of a 200 mW diode module. Erbium upconversion luminescence is characterized by the bands at 410, 523, 546, and 658 nm, corresponding to the 2H9/2 → 4I15/2, 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2.