Deterioration and film forming abilities of the slurries used for preparing La0.8Sr0.2MnO3 films through composite sol–gel method

The slurries, used for preparing La1−xSrxMnO3 (LSM) films through composite sol–gel method with citric acid, were made up of LSM particles and precursor sol with different pH values. The reasons and key factors for the deterioration of the acidic slurry were analyzed by XRD, SEM and TG/DSC. Furthermore, the LSM films were fabricated with different slurries for studying their film forming abilities. It has been found that the deterioration of the acidic slurry is determined by the abundant H+ ions, generated from ionization of the citric acid. Discoloration of the alkaline sol and slurry is considered as a result of complicated complexes of Mn2+ ions, which have a good effect on the film forming ability of the alkaline slurry, together with the complexes of La3+ and Sr2+ ions. The alkaline slurry has better long-term stability than the acidic slurry, and the films made from it are more homogeneous, thicker and have lower sheet resistance.

► H+ ions generated from ionization of citrate acid induce deterioration of the acidic slurry.
► Complicated complexes of Mn2+ ions bring on discoloration of the alkaline sol and slurry.
► The alkaline slurry has better long-term stability than the acidic slurry.