[Adam-2020 (OP)]

Hello

I am a new member here and this is my first topic post. Hope eveybody is alright.

I am trying to grow a spinel crystal material as a fun experiment. I am thinking of using two systems: Either Al2O3/Mno/P2O5 or Al2O3/Mno/Cuo. Do you guys think in those two systems, is there any of those that will melt under 1100 C?

Adam

[paul cotter]

Spinels are mixed metal oxides. The first one would give a phosphate mixed salt, not a spinel. Anyway p2o5(more accurately p4o10) is dreadful stuff to work with. It usually comes as a fine dusty powder that turns to glue on contact with atmospheric moisture and releases so much heat that spillage on paper or cloth can start a fire. To work with it you would need a glove box and a vacuum desiccator . The other combo might give a spinel, I don't know offhand. You would need to know the required stoichiometrics and a fierce source of heat to melt these refractory oxides.

[Adam-2020 (OP)]

Spinels are mixed metal oxides. The first one would give a phosphate mixed salt, not a spinel. Anyway p2o5(more accurately p4o10) is dreadful stuff to work with. It usually comes as a fine dusty powder that turns to glue on contact with atmospheric moisture and releases so much heat that spillage on paper or cloth can start a fire. To work with it you would need a glove box and a vacuum desiccator . The other combo might give a spinel, I don't know offhand. You would need to know the required stoichiometrics and a fierce source of heat to melt these refractory oxides.

What about this system Al2O3-Mno--Cuo-Na2O-Cao? Anything volatile or explosion or violent reaction happening?

[paul cotter]

I suspect that the last mix of metal oxides would give you a glass rather than a spinel. I am sorry that I can't be more helpful, I only answered because there were no other replies. Inorganic chemistry is not one of my best abilities. As far as I remember spinels follow some general rules and not every oxide mix will give a spinel. There should be plenty of information online. In general there is no great hazard in fusing metal oxides other than the high temperatures involved and you are not employing toxic oxides eg those of thallium, lead, mercury, beryllium, etc.

[Adam-2020 (OP)]

I have been  searching online about liquid eutectic temperature of the system Al2o3-Cuo and its eutectic composition but I don't  seem to find it. Does anybody havce an idea about this? or share any link with the answer

[chiralSPO]

How about cobalt oxide spinel? Co₃O₄, which can be made by hydrothermal synthesis.

I found a paper (unfortunately the manuscript its self behind a pay wall, but both some of the experimental data and the cover art and abstract are available). Granted, their crystals were microscopic, but that's ideal for their application, and it looks like they worked out some fundamental kinetics of the crystal nucleation and growth vs temperature and other controllable variables...

Abstract: The hydrothermal growth of cobalt oxide spinel (Co3O4) nanocrystals from cobalt acetate precursors was monitored with in situ powder X-ray diffraction (PXRD) in combination with ex situ electron microscopy and vibrational spectroscopy. Kinetic data from in situ PXRD monitoring were analyzed using Sharp–Hancock and Gualtieri approaches, which both clearly indicate a change of the growth mechanism for reaction temperatures above 185 °C. This mechanistic transition goes hand in hand with morphology changes that notably influence the photocatalytic oxygen evolution activity. Complementary quenching investigations of conventional hydrothermal Co3O4 growth demonstrate that these insights derived from in situ PXRD data provide valuable synthetic guidelines for water oxidation catalyst production. Furthermore, the ex situ analyses of hydrothermal quenching experiments were essential to assess the influence of amorphous cobalt-containing phases arising from the acetate precursor on the catalytic activity. Thereby, the efficient combination of a single in situ technique with ex situ analyses paves the way to optimize parameter-sensitive hydrothermal production processes of key energy materials.

https://chemistry-europe.onlinelibrary.wiley.com/action/downloadSupplement?doi=10.1002%2Fchem.201801565&file=chem201801565-sup-0001-misc_information.pdf

https://chemistry-europe.onlinelibrary.wiley.com/doi/epdf/10.1002/chem.201886961

https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.201886961

https://chemistry-europe.onlinelibrary.wiley.com/doi/full/10.1002/chem.201801565

[paul cotter]

Cobalt spinel is an interesting one. It is electrically conductive and has been used as an anode material in chlorate cells as one of the few alternatives to platinum, the others being magnetite, manganese dioxide, lead dioxide, graphite and ruthenium/iridium/titanium mixed oxide.

[Adam-2020 (OP)]

I found this diagram showing three different binary phase diagrams of systems Al2O3-Cuo, Al2O3-Tio2 and Cuo-Tio2.

It is in the attachment.

Based in these diagrams, how can I calculate the eutectic point of a new system Al2O3-Cuo-Tio2 from those three diagrams?

[Bored chemist]

The ones with titania in aren't very helpful.
The lowest liquid phase temperature seems to be about 1100 or 1150C
That's a lot better than you get with MgO/ Al2O3