Abstract
(ZrO2)0.89(Sc2O3)0.1(CeO2)0.01 crystals have been grown by directional melt crystallization in a cold crucible. The chemical and phase compositions of the crystals have been characterized using energy dispersion X-ray spectroscopy (EDX), Raman scattering spectroscopy and transmission electron microscopy (TEM). The X-ray photoelectron emission method has been used for determining the valence state of the Ce ions. We show that directional melt crystallization produces an inhomogeneous ceria distribution along the crystal length. The as-grown crystals are mixtures of cubic and rhombohedral zirconia modifications. The rhombohedral phase has an inhomogeneous distribution along crystal length. Melt crystallization does not produce single-phase cubic (ZrO2)0.89(Sc2O3)0.1(CeO2)0.01 crystals. The formation of the phase structure in the crystals for different synthesis methods has been discussed.
Highlights
Scandia-stabilized zirconia solid solutions have high oxygen ionic conductivity and show good promise for the production of solid-state electrolytes for electrochemical devices, e.g., solid oxide fuel cells (SOFCs)
We found that this synthesis method does not provide single-phase cubic crystals of the studied composition range at room temperature, which is contradictory to the phase analysis data for specimens synthesized using various ceramic technologies
In detail, the phase composition of the (ZrO2 )0.89 (Sc2 O3 )0.1 (CeO2 )0.01 (10Sc1CeSZ) specimen in this work and investigated the factors affecting the formation of the crystal structure in this synthesis method
Summary
Scandia-stabilized zirconia solid solutions have high oxygen ionic conductivity and show good promise for the production of solid-state electrolytes for electrochemical devices, e.g., solid oxide fuel cells (SOFCs). The formation of the rhombohedral phase in these specimens was attributed to a homogeneous distribution of the Sc3+ cations in the ZrO2 matrix, which is achieved due to a low heating rate (~2 ◦ C/min) during solid state synthesis and the presence of a small quantity of impurities [5] This may destroy the long-range order of the oxygen vacancies and favor the Crystals 2020, 10, 49; doi:10.3390/cryst10010049 www.mdpi.com/journal/crystals. In our previous work [11], we studied the structural and transport properties of (ZrO2 )1-x-y (Sc2 O3 )x (CeO2 )y solid solution crystals (x = 0.08–0.10; y = 0.005–0.015) grown by directional melt crystallization We found that this synthesis method does not provide single-phase cubic crystals of the studied composition range at room temperature, which is contradictory to the phase analysis data for specimens synthesized using various ceramic technologies. We report data on the behavior of Ce ions during the melt synthesis
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