Sagar Kumar Dutta

Depends on what you want to produce and from what precursors/reactants... Please provide more details. What chemical reaction(s) are involved?

Alan F Rawle, actually we want to prepare NI0.5 Cu0.2Al0.3Fe2O4 by using chloride salt of thus metal. Now, how we can calculate the molar ratio of thus salt for the chemical coprecipitation method.

Sagar Kumar Dutta

Your formula (NI0.5 Cu0.2Al0.3Fe2O4) does not make sense to me. Please use the correct symbols for the elements and also use subscripts in the formula - the whole line looks confused. I assume you mean NiO (nickel oxide) for 'NI0'. Or is it Ni 0.5[CuO] 0.2[Al] 0.3[Fe2O4] etc? I am unsure on 'AI0' - do you mean aluminum oxide? If so the formula for this is Al2O3. And Fe2O4? Is this a ferrite (or a spinel; no such thing as a ‘spinal’ other than Spinal Tap…Note 8/19/21: I see you've corrected the 'typo' in your question) or Fe2O3 (iron (III) oxide)? 'Chloride salt' is also not helpful. AlCl3 could not be worked with easily. The chlorides are normally in hydrated form. For example, aluminum chloride is normally found in the hexahydrate form. We need to know your exact proposed precursors or are we supposed to answer this as well?

A reference to a paper or a screen shot would be helpful. For a chemist this calculation should be trivial.

Sagar Kumar Dutta

OK, without responses from you it looks like I have to conduct some research of my own. Ideally we'd find a ternary phase diagram for NiO-CuO-Al2O3-Fe2O3 (to look at probable calcination temperatures) but this is unlikely and we have to work with more simple starting points.

Inputting your "NI0.5 Cu0.2Al0.3Fe2O4" into Google brings up this question (obviously!) and a paper (https://arxiv.org/ftp/arxiv/papers/1203/1203.3924.pdf BTW, I get a malicious virus security warning on this site) entitled 'Structural, magnetic, and optical properties of zinc- and copper substituted nickel ferrite nanocrystals'. Within this abstract we find a more believable and plausible formula: Ni0.5Cu0.5Fe2O4 on page 6 (even their formula has to be adapted - they show F2O4 at the end when we know it must be Fe for a ferrite... This incorrect 'typo' is also shown in the Google synopsis). So, I'm having to be a detective and work through that you're trying to say Ni0.5Cu0.2Al0.3Fe2O4 where the Cu0.5 in the original is partially substituted by aluminum to Cu0.2Al0.3. Am I correct? Clarity in chemical formulae is vital.

Inputting Ni0.5Cu0.5Fe2O4 leads to another article: 'Highly Sensitive Ni0.5Cu0.5Fe2O4 Nano Particles as an Ethanol Gas Sensor' Article Highly Sensitive Ni0. 5Cu0. 5Fe2O4 Nano Particles as an Etha...

This article is over a ridiculous $100 and I have requested the text from the authors.

In a further article - on another insecure site - (CuO-NiO Nano composites: Synthesis, Characterization, and Cytotoxicity evaluation http://www.nanomedicine-rj.com/article_24936_7ad37434d60d7bb3a13ce2e14b03b81b.pdf) we find for the CuO-NiO system likely (chloride) precursors to be NiCl2.6H2O, CuCl2.2H2O and the reaction proceeds with precipitation of the (mixed) hydroxides with NaOH followed by calcination.

An alternative nitrate decomposition route would be possible in my mind too and would be preferable as precipitation of the mixed chlorides could (with incorrect pH selection) result in the preferential precipitation of a single hydroxide and not an intimate 50/50 hydroxide necessary for a CuO-NiO equimolar system).

OK, back to: Ni0.5Cu0.2Al0.3Fe2O4 made from the following chloride systems:

• NiCl2.6H2O Molar mass: 237.70 g/mol
• CuCl2.2H2O Molar mass: 170.48 g/mol
• AlCl3.6H2O Molar mass: 241.43 g/mol
• FeCl3.6H2O Molar mass: 270.29 g/mol

Now you have all the information (the correct formula that I have deduced along with the molar masses) to calculate the masses of the precursors. Again I state that I feel a nitrate precursor route would be preferable as oxygen is already incorporated (as NO3-) in the system. A OH- precipitation route is not likely to lead to a stoichiometric mix of ingredients/elements in my view.

Sagar Kumar Dutta

Continuing the theme of hydroxide precipitation followed by calcination, simple study of the Pourbaix diagrams for the systems show that it will not be possible to fix a pH in order that you'll precipitate the molar proportions required for your 'material'. I feel that the nitrate route would be the only feasible route - plus it's simpler - dissolution followed by firing. I attach the requisite Pourbaix diagrams to illustrate my point.

Precipitating at higher pH's (e.g. 12 - 14) will lead to 2 issues, IMHO:

• Al2O3 is amphoteric and will re-dissolve at higher pH's
• Incorporation of significant Na+ into the lattice which is likely to be intractable and not removable by washing

Sagar Kumar Dutta

Here's a route via nitrates.

Sagar Kumar Dutta

One further point occurs to me and it encapsulated in the line: 'the Cu0.5 in the original is partially substituted by aluminum to Cu0.2Al0.3'...

Now, Cu is normally bivalent and aluminum is normally trivalent. So, this simple substitution will result in a chemical imbalance in the formula Ni0.5Cu0.2Al0.3Fe2O4 and a non-stoichiometric compound... Normally one would consider the substitution of a bivalent ion with another bivalent ion. What would be the outcome of attempting this (Al3+ for Cu2+) substitution? In my view, this would lead to mixed phases after calcination and either separated CuO or Al2O3. That is, a mixture rather than a single (pure) compound. Again study of an appropriate phase diagram would be recommended.

Dear Sirs,

I apologize, but the above formula is not correct because in the case of both trivalent or bivalent Fe, electrostatic equilibrium is not reached. It is necessary to consider the mixed valence of Fe and further, if the total proportion of trivalent elements exceeds 2, then it is necessary to introduce compensatory vacancy positions. Spinel phases can withstand a lot, but they have their own internal rules. The point is that with spinel phases, two variants are possible with smooth transitions between them. It is on the one hand a classical spinel (MgAl2O4), ie Me(II) Me(III) 2 O4 and on the other hand a maghemite structure (gamma Fe2O3), which is nothing but Fe(III) 8/3 vacc.1/3 O4 . If the correct formula can be put together, it will be easy to calculate the weights of the chemicals. It is only to be noted that maintaining the desired mixed composition of Fe ions can be difficult or unrealistic.

Dalibor Matýsek

I agree with what you say and hence my remark directly above yours. One simply can't substitute a trivalent atom for a bivalent one in the formula. However, one may expect a trivalent Al3+ ion to substitute for Fe3+ in the ferrite structure completely altering the valency balance. My conclusion was if the former was attempted then there would be separate phase formation.

Yes, my colleague. I agree, but for spinel phases, resp. ferrites replacement of divalent cations with trivalent is possible, but under certain conditions. This is mainly the presence of compensatory vacancies, holes in the structure.

I have the impression that our Bangladeshi colleague would like to synthesize something, but he doesn't know exactly what. I also have the impression that he does not know that it is possible to mix almost anything, but the fundamental condition is to find out what actually came about. This verification can be extremely difficult. We never know in advance what Mr Ostwald and his rules will do to the sample.

There is a huge amount of literature on ferrites.

For example, this is quite important

https://www.researchgate.net/publication/327626938_Nomenclature_and_classification_of_the_spinel_supergroup

This text is also very instructive

https://www.researchgate.net/publication/227713700_Structure_of_Spinel