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The article discusses the physicochemical principles for the production of alumina cements based on nickel and cobalt spinel. The results of tetrahedration of the CaO–Al2O3–CoO– NiO system, which undergoes changes due to solid-state exchange reactions in the hightemperature region of the CaO–Al2O3–CoO subsystem at a calculated temperature of 1439 K, as well as the decomposition of the Ca3CoAl4O10 ternary compound near 1530 K, are presented. Thermodynamic analysis establishes the stability of the conodes of the above system, allowing for its triangulation. Modifications of the subsolidus structure are combined and given for the temperature of 1530 K. All binary, ternary, and quaternary combinations thermodynamically stable in the subsolidus region of the system under study are presented. Topological graphs depicting the interconnection of elementary tetrahedrons, which allow the prediction of solid-state processes in multi-component systems, have been constructed. Based on the study of the structure of the CaO–Al2O3–CoO– NiO system, the possibility of technological forecasting of heterophase materials with high-performance characteristics is substantiated. [ABSTRACT FROM AUTHOR]

Phase equilibria of the Ti-Ga-Sn system have been determined at primary crystallization and at 1000 °C in the composition interval ~ 50-100 at.% Ti based on differential thermal analysis, x-ray powder diffraction, scanning electron microscopy and electron microprobe analysis. Partial liquidus and solidus projections, the melting diagram, a number of vertical sections, isothermal section at 1000 °C, as well as the reaction scheme (Scheil diagram) for the Ti-Ga-Sn system were constructed. A ternary compound Ti5GaSn2 (τ) (Nb5SiSn2-type structure, tI32-I4/mcm), found by us previously, forms by peritectic reaction L + Ti2(Sn, Ga) + Ti5(Sn, Ga)3-4 ⇄ τ at 1500 °C and has a wide homogeneity range from 9 to 23.5 at.% Ga at solidus temperature and from 4 to 34 at.% Ga at 1000 °C, and located along constant composition of ~ 62.5 at.% Ti. D88-type compounds Ti5Sn3 and Ti5Ga4 form a continuous solid solution, denoted Ti5(Sn, Ga)3-4, at all investigated temperatures. Ga-poor part of it (below ~ 12.5 at.% Ga) forms by an interstitial mechanism, while in the interval above ~ 12.5 at.% Ga it is a substitutional phase. Isostructural compounds Ti2Sn and Ti2Ga also form a continuous solid solution Ti2(Sn, Ga) at solidus temperatures, which decomposes with decreasing temperature. Meanwhile, at 1000 °C, one more continuous solid solution Ti3(Sn, Ga) forms between isostructural compounds Ti3Sn and Ti3Ga. [ABSTRACT FROM AUTHOR]

HfO 2 -based mixtures, such as HfO 2 -Al 2 O 3 , play an important role in high-power laser optics and metal oxide semiconductor devices due to their high laser damage resistance and high dielectric constant. However, comprehensive insights into the microstructure and chemical state of HfO 2 -based mixtures at the atomic level are limited, partly because the extremely large fourfold coupling constant of hafnium makes it difficult to characterize. Herein, the Al structures in HfO 2 -Al 2 O 3 mixtures were investigated and compared with that of Al 2 O 3 using solid-state nuclear magnetic resonance (NMR) spectrometry, time-of-flight secondary ion mass spectrometry (TOF-SIMS), and conventional spectroscopic and microscopic techniques. 27Al NMR spectra show that the Al coordination resonances in HfO 2 -Al 2 O 3 mixtures change with the Al content. The content of five-coordinate Al (Al V) is positively correlated with the content of ternary compounds, indicating that the Al–O bonds in ternary compounds tend to be connected at the five-coordinated Al site, which is further demonstrated through annealing experiments of HfO 2 -Al 2 O 3 mixtures. Further, the impact of the above microscopic properties on the macroscopic performance, such as wettability and optical bandgap, has also been explored. Our insights into Al coordination resonances and ternary compounds in HfO 2 -Al 2 O 3 mixtures may help understand the structure–function relationship of mixture coatings. [Display omitted] • The content of ternary compounds in HfO 2 -Al 2 O 3 mixture coatings is affected by mixing ratio and annealing temperature. • Mixing leads to a sharp increase in the content of five-coordinated aluminum. • Changes in the content of five-coordinated aluminum affect the wettability of the coatings. [ABSTRACT FROM AUTHOR]

This paper presents the results of our comprehensive study of phase equilibria in the Al–Fe–Mo system using DTA, X-ray diffraction, SEM and electron probe microanalysis. The liquidus and solidus projections were constructed. It is shown that the ternary compound Al 8 FeMo 3 (τ) melts congruently at >1500 °C and has a homogeneity range from 2 to 9 at.% Fe and from 23.5 to 25 at.% Mo. Isostructural phases (Mo), (αFe) and AlMo (W-type structure, cI 2 -Im- 3 m) at solidus temperatures form a continuous solid solution (αFe,Mo,AlMo). Unlike the AlMo binary phase, which is not retained by quenching, the ternary (αFe,Mo,AlMo) phase is easily quenched due to its lower decomposition temperature. Among the binary based phases, the Al 8 Fe 5 (ε) phase has the widest homogeneity region, which extends up to 24 at.% Mo at solidus temperatures. It is shown that the addition of Mo stabilizes the Al 8 Fe 5 (ε) phase, and the temperature of its formation in the ternary system increases to 1331 °C in contrast to 1234 °C in the binary. Moreover, according to XRD data, the Al 8 Fe 5 (ε) phase in the ternary system has a rhombohedral structure of the Al 8 Cr 5 -type (hR 78- R -3m), rather than cubic Cu 5 Zn 8 -type structure (cI 52- I -43 m), like the binary one. A new binary compound Al 45 Mo 7 was identified for the first time. Its crystal structure is established as monoclinic Al 45 V 7 -type (mS 104- C 2/ m) with the lattice parameters a = 20.534, b = 7.561, c = 10.910 Å, β = 107.33. It was shown to form by peritectic reaction L + Al 5 Mo ⇄ Al 45 Mo 7 at ∼800 °C. Iron additions stabilize the Al 4 Mo phase, which in the binary system is stable above 942 °C. [Display omitted] • Phase relations in the ternary Al–Fe–Mo systems over the whole concentration range were studied. • A new binary compound Al 45 Mo 7 with a monoclinic Al 45 V 7 -type structure was found. • It is shown that the ternary compound Al 8 FeMo 3 (τ) melts congruently at >1500 °C. • A continuous solid solution (αFe,Mo,AlMo) (W-type structure) was found at solidus temperatures. • Fifteen four-phase invariant reactions are found,one is of peritectic type and fourteen ones are of U-type. [ABSTRACT FROM AUTHOR]