Phase equilibria in the system MgO-TiO_2

Abstract

W. Coughanour and V. A. DeProsseThe phase relatio ns in t he syste m :VJgO-TiO, we re studi ed by means of , oli d -phase r eactions between t he co mpone nts and by obse rving t he fu sio n cha racterist ics of s pecimens within t he syste m. The ex isten ce of three binary compounds in t he sys te m was con firm ed . F rom the data obtain ed, an equilibrium diagram for t he syste m is s ugges ted .

Experimental study of phase equilibria in the Al2O3–MgO–TiO2 system and thermodynamic assessment of the binary MgO–TiO2 system

“…As mentioned above, new thermodynamic description for the MgO–TiO 2 system needs to be derived and detailed review of available experimental data is presented below. The first phase diagram of the MgO–TiO 2 system constructed by Coughanour and DeProsse presented a congruent melting of all 3 intermediate compounds Mg 2 TiO 4 , MgTiO 3 , and MgTi 2 O 5 and 4 eutectic reactions. However, in later works it was found that only MgTi 2 O 5 melted congruently while Mg 2 TiO 4 and MgTiO 3 melted with decomposition.…”

“…It is not clear if there is a contradiction between these results or there is a solid‐state reaction occurring between 1273 and 1373 K. The liquidus surface of this system with 2 invariant eutectics at 1843 and 2003 K was constructed by Berezhnoi and Gul'ko based on the melting information obtained using the method of downfall of pyramids prepared from oxide mixtures heat treated at 1473 K. Microstructural investigation of the melted samples was not reported. It should be mentioned that the binary MgO–TiO 2 diagram accepted in the experimental work was not consistent with the latest data: the melting character of Mg 2 TiO 4 and MgTiO 3 was different and the melting temperatures of the intermediate compounds seem to be too low. Therefore, the results need to be verified.…”

Spinel solid solutions in the systems MgAl2O4–ZnAl2O4 and MgAl2O4–Mg2TiO4

“…The cubic unit cell parameter for the abovementioned compounds, as reported in the literature, varies in the limits 8.081-8.090Å for MgAl 2 O 4 , 1-3 8.086-8.088Å for ZnAl 2 O 4 , 1,4 and 8.40-8.440Å for Mg 2 TiO 4 . Magnesium titanate melts congruently at 1835 ± C 11 and 1732 ± C, 12 The compounds MgAl 2 O 4 , ZnAl 2 O 4 , and Mg 2 TiO 4 were obtained by solid state synthesis from the corresponding oxides MgO, ZnO, Al 2 O 3 , and TiO 2 . 5 According to the data of various authors, magnesium aluminate melts at temperatures of 2105 ± C 6,7 and 2135 ± C, 2,8,9 whereas zinc aluminate melts at 1950 ± C 10 ; for both compounds the melting type is congruent.…”

Solid-state reactions and dielectric properties in the system magnesia-lime-tin oxide-titania

“…On the binary joins, th ere was a regular variation of the temperature coefficient of [{ with composition. For example, see figure 10. A few specimens showed a small negative TOK, and two specimens had a positive value.…”

“…For differ ent specimens of the sam e gross composition, additional variations of K -values result from factors such as differences in firing sr,h edules, purity of raw materials, etc. Three binary compounds are known to exist in the MgO-Ti02 system [10] . Thoy are 2MgO·Ti02, :MgO·TiOz, and MgO·2Ti0 2• There is no solidsolution development in this system.…”