Fabrication and properties of La modified AZO powders via a gaseous penetration processing

A new kind of AZO powders were synthesized by co-precipitation method with the doping content of Al was 3.0 wt%. Further modification of La to the powders was done via a gaseous penetration processing. Changes in constitution, structure, and electrical conductivity caused by doping and penetration were characterized. The doping of Al lowered the resistivity of AZO powders from over 1×1014 (ZnO made domestically) to 4.24×107 Ω·cm. But more effective modification via gaseous penetration processing decreased the resistivity of La penetrated AZO powders to the lowest point of 2.45×105 Ω·cm. The optimal penetration conditions coordinated by orthogonal test were that La3+ content of the penetration solvent was 2.0 wt.%, and that the penetration processing lasted for 5 h at the temperature of 480 °C. XRD analysis demonstrated that the doping process of Al only leaded to the changes of the peak width and intensity without new phases appearing. Yet, new phases appeared after the processing of gaseous penetration of La, which indicated that La enter the AZO powders thus complex reactions occurred to form the extra compounds. EDAX analysis, coupling with XRD, provided the evidence that La did exist in the penetrated AZO powders and the potential sign of the generation of extra compounds. Through SEM images, it was illustrated that the gaseous penetration processing progressed the growth of grain size in the shape of rod and generated distinguishable phases of extra compounds.