Effect of Electrode Materials on Lead Lanthanum Zirconate Titanate with Heating under Reduced Atmosphere

Abstract

To understand the ferroelectricity degradation of ferroelectric random access memory (FeRAM) capacitor under hydrogen atmosphere, reactions between lead lanthanum zirconate titanate (PLZT) and the electrode materials, such as platinum (Pt) and iridium oxide (IrO2), were investigated by thermal analysis. The PLZT powder was decomposed by heating under Ar+3%H2 atmosphere at 1000°C with lead (Pb) metal, PbO, ZrTiO4 and TiO2. The decomposed PLZT with Pb metal exhibited perovskite phase after annealing under air atmosphere at 1000°C and no pyrochlore phase was observed. We found that Pt reacted with the Pb precipitated from PLZT by heating under Ar+3%H2 atmosphere. Consequently, a large amount of PbPt alloy and a small amount of PtPb4 alloy were formed. The formation temperature of the alloys was lower than the decomposition temperature of PLZT without Pt. Pt was directly involved in the decomposition of PLZT. However, no alloys of Ir and Pb were formed in the mixture of PLZT and IrO2 under Ar+3%H2 atmosphere. The heat treatment of the mixture of PLZT and the electrode powders indicated that Pt promoted the decomposition of PLZT under Ar+3%H2 atmosphere and IrO2 reduced the rate of the decomposition.