Archives of Metallurgy and Materials

Abstract

The aim of the work was to obtain thin bismuth oxide films containing, at room temperature, the Bi 1,5 Er 0,5 O 3 phase. This phase corresponds to the structure of the high-temperature δ-Bi 2 O 3 phase, in pure bismuth oxide, characterized by the highest ionic conductivity of all known solid state ionic conductors. The high-temperature δ-Bi 2 O 3 phase with the face centered cubic structure, in pure bismuth oxide, occurs only at temperature above 730°C.Stabilization of the δ-Bi 2 O 3 phase at room temperature was achieved by an addition of the erbium together with the employment of the Pulsed Laser Deposition (PLD) technique. The influence of an amount of Er alloying and the film thickness on surface morphology, microstructure, phase composition of thin films were investigated. The velocity of deposition of thin layers of bismuth stabilized with erbium in the PLD process using the Nd: YAG laser was about 0.5 nm/s.The investigation results of erbium doped bismuth oxide thin films deposited onto (0001) oriented Al 2 O 3 monocrystalline substrate are presented.Thin films of uniform thickness, without cracks, and porosity were obtained. All deposited thin films (regardless of the film thickness or erbia (Er 2 O 3 ) content) exhibited a columnar structure. In films stabilized with erbium, up to approx. 250 nm thickness, the columns have a diameter at the base from 25 to 75 nm. The columns densely and tightly fill the entire volume of the films. With increasing of the film thickness increases, porosity also significantly increases. In thin layers containing from 20 to 30 mole % Er 2 O 3 the main identified phase at room temperature is Bi 1.5 Er 0.5 O 3 . It is similar to the defective fluorite-type structure, and belongs to the Fm-3m space group. This phase corresponds to the structure of the high-temperature δ-Bi 2 O 3 phase in pure bismuth oxide.