Influence of the concentration and lanthanoide type on the phase transitions in Ln(2)O(3)-MO2 system (Ln = La, Gd, Y; M = Zr, Hf)

Influence of the concentration and type of rare-earth oxide on the chemical composition and structure of the compounds formed in the "Ln(2)O(3)-MO2" system has been investigated by X-ray powder diffraction and Raman spectroscopy. It was found that crystallization temperature of synthesized powders rises with an increase in the concentration of Ln(2)O(3). Besides, it was revealed that the efficiency of stabilization of high-temperature phases (tetragonal and cubic) in Ln(2)O(3)-ZrO2 systems increases with the introduction of RE cations in the La3+ -> Gd3+ -> Y3+ series in accordance with the increase in the solubility of Ln(2)O(3) in ZrO2. A similar behavior was also observed for the Ln(2)O(3)-HfO2 systems. Finally, we established that the compounds formed in Ln(2)O(3)-HfO2 systems have a greater ability to crystallize in the monoclinic phase.