Melt growth, structure and properties of (ZrO2)1−(Sc2O3) solid solution crystals (x=0.035−0.11)

Crystals of (ZrO 2 ) 1− x (Sc 2 O 3 ) x solid solutions with x =0.035, 0.06, 0.09 and 0.11 have been grown for the first time using the directional crystallization technique. Analysis of the scandium distribution along the crystal showed that the composition of all specimens is homogeneous, and the Sc 2 O 3 concentration is almost identical to its content in the charge. All specimens exhibit a little decline in the scandium concentration along the crystal, this indicating that the effective distribution coefficient Sc is slightly greater than 1. The structure of as-grown crystals has been studied as a function of the Sc 2 O 3 stabilising oxide concentration by X-ray diffraction, transmission electron microscopy and Raman spectroscopy. Crystals containing 3.5 mol% Sc 2 O 3 are a mixture of the monoclinic and tetragonal phases, the crystals containing 6 mol% Sc 2 O 3 have a tetragonal structure, those with 9 mol% Sc 2 O 3 have the tetragonal phase with inclusions of the rhombohedral one and the specimens with 11 mol% Sc 2 O 3 represent the rhombohedral phase with inclusions of the cubic phase. The electrical conductivity was measured as a function of temperature by electrochemical impedance spectroscopy. The conductivity of the scandia stabilized crystals, in spite of their inhomogeneity, presence of stresses and low fracture toughness, is comparable with that of the yttria stabilized zirconia crystals.