Influences of Na on sintering of Cu(In,Ga)Se2 quaternary ceramic targets

• A high quality Na-doping CIGS target was fabricated by hot pressing sintering.
• The action mechanism of additional Na in CIGS target was investigated.
• Na segregates on the grain boundaries of CIGS in the form of Na2Sex after sintering process.

Cu(In,Ga)Se2 (CIGS) quaternary ceramic targets for sputtering use were fabricated by sintering from Cu2Se, In2Se3, Ga2Se3 and NaF mixed powders. The influences of Na concentration and sintering temperature on microstructure, crystal growth, fracture, and density were examined. And Na action mechanisms were analyzed. SEM, EDX, XRD and XPS were employed to characterize the morphologies, compositions, microstructure, and chemical states, respectively. The targets sintered by pressureless sintering are porous and brittle and the additional Na induces the delamination of the target. As for hot pressing sintering, the results show that the targets possess of chalcopyrite structure with (1 1 2) preferred orientation. They have higher densities and finer grain sizes than the targets sintered by pressureless sintering. The additional sodium facilitates the crystallization of CIGS targets. Sodium distributes mainly on the grain boundary in the form of Na2Sex, which can induce the disintegration of CIGS targets. The delamination of CIGS targets appears when the content of NaF is over 1.0 mol%.