Stability of Solid-Solution Phase and the Nature of Phase Separation in Ru–Zr–O Ternary Oxide

Abstract

Equilibrium phase diagram of ruthenium–zirconium oxide (Ru–Zr–O) was calculated by a combination of ab initio density functional theory and thermodynamic calculations. The phase diagrams suggest that the solubility between ruthenium oxide and zirconium oxide is very low under normal experimental conditions, in good agreement with the prior reports in literature. Also provided is the theoretical support for the reported phenomenon that doping or amorphization of Ru–Zr–O might suppress phase separation of the oxide. To study the spinodal decomposition of Ru–Zr–O, we successfully prepared an amorphous Ru0.48Zr0.52O2 film of a solid solution phase by a thermal decomposition at a low temperature (563 K). In situ transmission electron microscopy was utilized to witness the spinodal decomposition of the amorphous Ru0.48Zr0.52O2 solid solution by electron–beam annealing. The present fundamental study of the phase behavior of Ru–Zr–O provides a guideline for the phase and microstructure design of Ru-based mixed oxides for various important applications.

Stability and spinodal decomposition of the solid-solution phase in the ruthenium–cerium–oxide electro-catalyst

“…29 Three different semi-empirical O-T relationships are compared: linear, exponential, and their average. 41,42 Consistent with prior reports, 21,31,43 O in the range of 10-25 kJ (mole atom) À1 does not distinctly affect the prediction of the miscibility gap of the Ru-Ce-O system. O B 10-25 kJ (mole atom) À1 has been estimated for a variety of hard materials at temperatures close to their melting points or decomposition temperatures.…”

“…In comparison, exponential models (O = H 0 exp ÀT/t ) may describe more complex behaviors and give good approximations for most binary systems. With the exponential model for instance, the G-x relations of (Ru 1Àx ,Ce x )O 2 at varied temperatures can be obtained based on eqn (9), (10), (20), (21), (30) and (31), the lattice instabilities and the results in Table 3. With the exponential model for instance, the G-x relations of (Ru 1Àx ,Ce x )O 2 at varied temperatures can be obtained based on eqn (9), (10), (20), (21), (30) and (31), the lattice instabilities and the results in Table 3.…”

“…0 G R RuO 2 , 0 G hcp Ru , G g O 2 , 0 G R CeO 2 , 0 G Ce as a function of composition and T can be obtained by fitting the thermochemical data of pure substances in ref. Given the same peritectic temperature (T p ) of Ru-Zr-O and Ru-Ti-O at 1700 K, 21,47 here we assume the peritectic temperature for Ru-Ce-O to be 1700 K. The hypothetical T p -x curve intersects the miscibility gaps predicted in Fig. Then T d (R-RuO 2 ) = 1685 K and T d (F-CeO 2 ) = 5880 K are obtained according to eqn (36) and (37).…”

Adding a Spinodal Decomposition Retarder: An Approach to Improving Electrochemical Properties of Ruthenium–Tin Complex Oxides

“…4 (in the unit of kilo Joules per mole of atoms) using an exponential temperature dependency of interaction parameter. 20,22 ( …”

“…This is also a challenge for many other RuO 2 -based complex oxides that are characteristic with a large driving force for spinodal decomposition. 19,20,22 In the present study, we have developed a novel scalable approach to retarding spinodal decomposition in the synthesis of Ru-Sn-O by c Present address: International Business Machines a thermal decomposition process. We introduced a certain amount of preformed nano-crystalline SnO 2 into the final precursor mixture used to prepare the Ru-Sn-O coating; the added SnO 2 effectively retarded spinodal decomposition of an initial (Ru 1-x ,Sn x )O 2 solid solution phase during the thermal treatment.…”