Zirconates of the rare earth elements and their physicochemical properties Communication 3. Some principles of the formation, physicochemical and technical properties of zirconates

Conclusions

• 1. The mechanism of the formation of zirconates during coprecipitation from salt solutions is the same for all the rare earth oxides that we investigated. The height of the peaks of the first exothermic effect, due to the crystallization of the rare earth zirconate from an amorphous coprecipitation product, decreases in the series La₂O₃→ (CeO₂) → Pr₂O₃ → Nd₂O₃ → Sm₂O₃ → Y₂O₃ → Yb₂O₃. This corresponds to a decrease in the reactivity of the indicated oxides with respect to zirconium dioxide.

• 2. Zirconium dioxide apparently forms compounds Ln₂Zr₂O₇ (where Ln is a rare earth element), with pyrochlore structure, with all the oxides of the trivalent rare earth elements.

• 3. The investigated zirconates, with the exception of Ce₂Zr₂O₇, are stable to heating in air.

• 4. The physicochemical properties of the rare earth zirconates: lattice parameter, x-ray density, specific gravity, index of refraction, and melting point, are closely dependent upon the atomic number and upon the ionic radius of the rare earth element.