Undoped and Fe doped Lanthanum Oxide (La2O3) Nanostructures were synthesized in our lab via co-precipitation route.
The SEM results showed mixed morphology of nanosheets and nanoparticles in case of undoped Lanthanum Oxide (La2O3). But, by 1% Fe doping, the morphology started changing to only nanoparticles. By 3% Fe doping, almost all nanoseets (which were observed in undoped sample) changed to only nanoparticles. Can anybody please explain the reason of this change in morphology?
A first question: did you obtain your crystals from solution growth ?
A second one: What's about the structure of La2O3 ? Cell parameters, symmetry? Space group ?
Third point: It is possible that, when adding Fe ions in the growth medium , 2D layers of Fe2O3 of FeO, of Fe3O4 forms onto the growing surfaces of La2O3.
If you like, I can investigate for you this aspects, but more information is needed about your crystallization route.
All the best
Dino Aquilano
Dear Dr. Ali:
The Co-precipitation method of chemical synthesis is a classical method or one of most classical method of synthesis chemical representing a direct advance under the precipitation method.
A priori this method of synthesis has similar functionality to another methods having as prime intention to provide further chemical homogeneity at a compounds with two or more cationic species, since proportions between component cations close to unities or reaching doping at part per billion level or lowest are critical at mechanical mixture of oxides. In classical mechanical mixture of oxides, a great proportion between constituent oxides or the presence of a constituent at fraction equal to or lower than mili-mol imply in difficulty at processing of homogeneous material.
In a general way, the synthesis of oxides of earth-rare elements type Ittria, Zirconia and Lanthana presents, several critical points.
See, in the name Co-Precipitation, the prefix “Co” means that two or more cation will go to precipitate from solution simultaneously. This condition is a sine qua non condition to the success of this method of synthesis. Therefore, an absolute pH control is necessary. In the same way, there is an optimum temperature of synthesis, also.
According to the previous information, during the Lanthania synthesis, Precipitation method, a double shape of particles was prepared. This event sound a bit strange, since in a general way, the Precipitation method gives sub-micrometric spherical particles. In this sense, as a whole this type of method should be optimized at synthesis apparatus and chemical reagents disponible. In another words, nitrate or sulfates salts require adjusts different of synthesis parameters, those when carbonate salts are the chemical reagents. Thus, I suggest you revise stoichiometric calculus, temperature control, pH and agitation level. As mentioned above, the PH control drop-by-drop is critical.
As mentioned in previous information, after the procedure of doping with iron cation, Co-Precipitation method, powder retrieve previous expectative of a single-shape of spherical particles sub-micrometrics. This event might be interpreted as further indicator for that pH was maintained more close to one pH ideal that during Precipitation method. Thus, seems that pH derived for synthesis or its control would be affect the optimal synthesis parameters.
Kind regards
Marcos Nobre (M. A. L. Nobre)
Sir Dino Aquilano,
These sample were synthesized via co-precipitation method (solution growth).
Crystallite size of undoped La2O3 was 43 nm, for 1% Fe doped samle, it was 35 nm while for 3% Fe doping it was 34 nm as calculated by Scherer formula. The structure of La2O3 nanostructures was monoclinic as matched with standard pattern of La2O3.
The intensities of diffraction peaks were enhanced with Fe doping which indicates the improved in crystallinity. However, there is shift in major peaks of XRD patterns toward lower angle as function of Fe dopant concentration.
I need reason for this change in morphology with reference of any published paper.
Thanks for your concern.
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