Experimental Investigation and Thermodynamic Modeling of the ZrO₂–MgO System

Abstract

where n S is the stoichiometric coefficient of the sublattice S, y S J is the site fraction of the constitutent J in the sublattice S, and R is the gas constant. 0 G end is the Gibbs energy of the end-members, which are the stoichiometric compounds formed by the constituents when each sublattice is occupied by only one species, e.g. (C 1 ) u (A 1 ) v . . .. Those 0 G end are to be determined in the optimization. The excess Gibbs energy E G m is expressed by:

Phase Equilibria in the ZrO2–MgO–MnOx System

“…It should be mentioned that the minimal oxygen partial pressure which can be reached in our DTA device using He‐atmosphere is 10 −4 bar . At this partial pressure, according to results of our earlier studies, the MnO + O 2 →β‐Mn 3 O 4 transformation occurs at 1487 K. Though the small heat effect observed at 1481 K on cooling was related to formation of the β‐Sp phase in MnO x –rich region the TG curve did not indicate oxygen uptake upon cooling. The oxygen uptake is probably rather slow due to small concentration of O 2 in the protective gas.…”

“…To assess the influence of the O 2 partial pressure on phase equilibria in the ZrO 2 –MgO–MnO x system additional investigations were performed at 1923 and 1523 K under inert gas atmosphere. As we already reported using an inert gas atmosphere allows us to decrease the oxygen partial pressure down to 10 −4 bar.…”

“…The phase equilibria between t‐ZrO 2 and c‐ZrO 2 were not established. However, according to the analogous binary phase equilibrium in the ZrO 2 –MnO x system at 1913 K does not visibly depend on the O 2 partial pressure. Therefore, we supposed that the t‐ZrO 2 + c‐ZrO 2 two‐phase field at low is similar to that observed at air conditions.…”

Bifurcation and "self-organization" of a system

“…The compounds formed by the reaction (3) 6 .18H 2 O (#82). All of these compounds are tending to the natural structure or the equilibrium state, i.e.…”

“…The phase diagrams enables widely consider problems of physical chemistry and chemical thermodynamics, reflecting modern ideas about the properties of individual substances as well as their mixtures, phase and chemical equilibria, and surface phenomena jointly. They are widely used in search of new intermetallic compounds [3][4][5], the glass-forming systems in the crystalline, glassy and molten states [6][7][8], solid solutions [9,10], predicting of the properties of metastable states [11][12][13] , analysis of phase transitions and critical phenomena [14,15], the fabrication of composite materials [16,17], the processes of separation and purification of substances [18,19], the development of algorithms for constructing phase diagrams [20][21], and others [22][23][24][25] presently.Study of the phase diagrams implies partitioning of the multidimensional figures on individual cells -media of the invariant points which are called triangulation. The topological [1,2], geometric [26,27] and thermodynamic [28,29] triangulation techniques are available at this moment.…”