Lanthanum zirconate formation

Thermodynamic calculations by Yokokawa et al. [12] showed that LSM may react with YSZ to form La2Zr207 or SrZrOs if the activity of La or Sr become high even though they are in their stability region. The formation of lanthanum zirconate pyrochlore phase at the LSMA SZ interface is detrimental to the electrochemical activity and performance of the electrode because the conductivity of this phase is about 2.5 orders of magnitude lower than that of YSZ [1],... 

Reaction of Perovskites with the Zirconia Component in YSZ The L3203 component in perovskite can react with the zirconia component in YSZ to form lanthanum zirconate, La2Zr207. On reaction, the valence state of the transition metal ions, may change as a result of the formation of other transition metal binary oxides ... 

Pressure sintering techniques have also been used to fabricate transparent lanthanum-doped lead zirconate titanate (PLZT) ceramics in air and in oxygen-gas atmosphere [31]. The microstructure of the sintered body was not uniform it was completely dense near the surface, but it was porous at the center. The thickness of the dense layer increased with sintering time and oxygen-gas pressure in the sintering atmosphere. Vaporization of PbO from the specimen surface and resultant formation of lattice vacancies were attributed to this microstructural evolution. Diffusion of the gas trapped in the pores was also important in determining the thickness of the dense layer. When the PLZT specimen was sintered in air at 1200 °C for 8 h, the thickness of the dense layer was 0.25 mm. Therefore, if the specimen thickness was 0.5 mm, the whole specimen was dense and transparent. When the specimen was sintered in an oxygen-gas atmosphere under the same conditions, the specimen thickness increased markedly. 

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