Simply, a very small amount of the "second element" or "dopant" is added to the host lattice without developing a new phase. In alloying, the addition is much larger and two or more phases may coexist. The following threads will help you to understand more about these two terms.

https://www.researchgate.net/post/What_is_the_difference_between_doping_and_alloying_in_metallurgy2

https://www.researchgate.net/post/What_is_the_difference_between_alloying_and_doping_which_process_alloying_or_doping_changes_lattice_parameter

https://www.researchgate.net/post/What_is_the_difference_between_doping_composite_and_alloy

https://www.researchgate.net/post/What_is_difference_between_doping_and_alloy

https://www.quora.com/What-is-the-difference-between-composites-alloys-and-doped-materials

Dear Franclin,

generally, doping is a method to change the conductivity of a pure material, as an example: boron (p-type) in silicon or phosphorous (n-type). Furthermore, optical properties are changed by doping - colour centers and so on. The host lattice stays unchanged. Doping produces energy states within the band gap. At high doping concentrations it can be almost have the character of an alloying.

Alloying means the mixing of two or more materials (mostly by melting), generally at higher concentrations. This is a very old technology of mankind, as an example alloying of copper and zinc - giving brass or copper and tin to bronze. Almost prehistoric men have done this. If you alloy silicon and germanium to SixGe1-x you get a continuos change of bandgap and other properties. Normally you have a defined crystal structure but the properties are statistically broadend due to the statistical nature of mixing.

The x means: the mixing is not stoichiometric - the mixing is continuos, not in the ratio of integer numbers. Of course the conductivity can change by alloying too. Not all materials can be alloyed completely. This depends on the crystal structures and their actual parameters.

Yours

R. Mitdank

Doping results a perturbation in the structural and electronic properties. A very small amount of element comparable to the base element is introduced. Actually, the second element i.e., dopant acquire position of of lattice site of the base element or any interstitial site as defect.

Whereas, Alloy means simply mixing of two elements. Two iso-electronic and isostructural elements are generally used to prepare alloy. Different percentage of alloying material are used to prepare alloy. But, only small amount of material can be added in doping.

Doping mainly modifies the properties of the base element. But, a different properties may grow-up in alloying.

Dear Mohammed M. Obeid

I just wanted to know if there were a more rigid definition of what a doping is, in comparison to an alloy ... i.e. the maximum concentration of impurities, the limit in size of the impurity , or the maximum change (in %) of the lattice parameter due to the impurity, Do you know what I mean ?

For instance, regarding to your definition ,, what would be : "a very small of dopant"? are there some magnitud or relative concentration(number) attached to this definition ? Regarding to this part, I would belive it depends on the impurity and on the type of atoms which form the host lattice. Since a tiny concentration of a big atom as At in a lattice of small atomic radii atoms is not the same as to substitute a small atom as P in a size-like atoms lattice ....

So. Do you think there's a criteria, regarding the maximum level of impurities' concentration, which helps to the explanation of the concept ?

About the concept of "phase" that you mentioned. I also had a similar idea, but had understood that instead of speaking about formation or modification from one phase to another (or building a new phase), we should speak about a modification of the crystalline structure of the material, instead of defining the concept with the term "phase". Since we know phase is not equal to atomic/crystalline structure.

So, I would ask the same regarding this point: Is there a fix criteria about how much the lattice parameter of a structure can change before we observe an effect of modification of the structural lattice as if we were introducing so much impurities to become transforming the material to an alloy ?

Dear Rüdiger Mitdank :

You provided a bunch of useful information we can use to comprehend the differencen between both concepts ! Thank you !

Can you read the above paragraphs of this reply ...

What do you think ? What "higher concentrations" mean ? Or, do you think is there a criteria regarding to this, which can support the definition ? What the limit of a "high doping concentration" would be ?

And, regarding to the magnitud in the modification of the atomic structure due to the dopants/impurities ... can you say something about it ? What term would you use ? .. " Atomic(crystalline) structure/lattice , or "phase" ?

Dear Kartick Malik :

There is not a change in the electronic properties between the base material and its Alloy ?

I did like your last sentence: "Doping mainly modifies the properties of the base element. But, a different properties may grow-up in alloying"

What can you say about the concerns I expressed on the first paragraphs of this reply ?

Regards All !

Thank you for your valuable discussion! :)

I think that there is no general rule. This is vary from system to another. The solubility of the dopant in host lattice (thermodynamically stable) may be depend on ionic radius of dopant and the cation/anion of the host lattice, electrongativity, crystal systems of the end compunds, temeprature, synthesis route, environment, crystal size ( small crystal size is easly to be distorted even at a very low doping concentrations). When the concentration of the dopant is greater than the solubility limit in the host lattice, then segregation occurs at grain boundaries. You can find more about this aspect in literature.

Dear Mohammed M. Obeid

Thank you !, as you mention, is important to considere other variables! and is nice to have at least a general knowledge of what those other variables could be

Thank for extending your reply

:)

Doping means the addition of a dopant to the material (any material; metals or nonmetals, or semiconductor); and this dopant may be substitute host ions of the structure or occupying in the interstitial sites; depended on ionic radius.

An alloy means the addition of element or elements (metals or nonmetals) to element metal.

Dopants are commonly added in very small concentrations. They may be substitute into the host crystal lattice without changing the parent phase. But, alloying species may result in the formation of new phases. The aim of the doping is to improve the certain properties without altering the main characteristic of the host material, while alloying is behaving as a new material with new properties.

Dear Moslem Latife Alhussainy :

Both processes; either Doping or alloying can involve the insertion of a foreing element/atoms into the atomic sites at the host lattice (these normally occupied by another atoms or atomic species speaking in the more general scenario). This is substitution.

Although in the Alloys-synthesis scenario the foreign element can also be added into interstitials sites in the atomic lattice

For instance, we can produce a bulk material Al2O3-base, introducing an element as Cu, Au, Ag or Pt. If we can make these components got into the atomic sites of the crystalline lattice (replacing some of the Al and/or O atoms), this substitution may modify the lattice parameters, even produce a change in the crystalline system of the compound, but even still, the atoms in the atomic sites can be bounded with covalent bonds too, and avoid been positioned into interstitials sites, or forming new compounds... Despite the Cu, Au, Ag or Pt atoms would be at the positions of the atomic sites of the lattice, replacing the base atoms , this would be an Alloy

Kind Regrads ! :)