To what phases can they belong?
CeO2 film was obtained on SrTiO3(001) substrate by the Polymer - Assisted Sol - Gel Deposition deposition method using polyvinylcaprolactam (PVCL) as the polymer. Before the deposition, the sol stabilized by the polymer was stored in air for approximately 3 hours until Ce(OH)3 completely transformed to CeO2. Specimen was annealed for an hour under 1000º in static air for an hour, then quenched from 900 C. The XRD pattern showed unidentified peaks at 31 and 35 degrees. Moreover, they are not occurred if the specimen was annealed in a gas flow.
Article New Parameter in Polymer- Assisted Sol- Gel Deposition
Dear Dr. Kenneth M Towe,
The peak at 28.6° 2-theta corresponds to the (111) planes of CeO2(5.41 Å), while the peak at 33.1- to (100) planes of CeO2(for the second order reflection, the first one is forbidden). The synthesized material was ceria.
Data XRD
Dr. Kenneth M Towe, It is a CeO2 thin film with grains oriented in just 2 directions- either or . The strongest peak for the former is CeO2(200), for the latter is CeO2(111).
Regarding the peak at 5.41 Å, I provided the calculations. The first peak at 16.37° 2-theta will not be shown due to the destructive interference.
And I do not know what CeO2 ("cerionite") is. Neither Google do. Could you provide any information about it?
Regards,
Mikhail
Dr. Kenneth M Towe, I am afraid, the films cannot contain cerianite a priori, but thanks for your answers. It was interesting to read about a new mineral to me.
Dr. Kenneth M Towe, I do not think that it is a case of a new mineral. I do believe that those peaks correspond to phases more or less connected with the mother phase that is CeO2. They could be non-stoichiometric CeO2 phases since the phases can be obtained by the reactions like the following:
3CeO2+2Ce2O3 → Ce7O12;
7CeO2 +2Ce2O3 → Ce11O20;
4CeO2+Ce2O3 → Ce6O11.
and I saw papers in which Cerium(III) oxide phases were found in experiments where CeO2 was the desired phase(it is concerned with oxygen- less environment while growth, ceria is easily reduced in reducing atmosphere).
Alternatively, these peaks could belong to adducts of reaction between CeO2 and the products of the polymer(polyvinylcaprolactam) decomposition since they were observed for the sample that was obtained by annealing in static air(probably the products of the polymer decomposition were not diverted properly). An analogue of this in case of the specimens that were obtaining using the shaking may be that the polymer was buried under the formations of the CeO2 particles.
Maybe the presence of the Ce2O3 phase (that is presumably responsible for the formation of the phases corresponding to the unidentified peaks) is the result of the sizes of the initial CeO2 particles. I saw papers in which Ce2O3 was considered as the most stable phase for the Crystallite with a certain size ca. 1.5 nm. So, maybe the crystallites did not agglomerate when they should do so.
I could find links if it is needed.
Moreover, it could be just an error made by the operator of the diffractometer. We cannot avoid such variant however, as it could be seen from figure I posted 2 answers earlier, this result was reproducible(however, within the frameworks of one laboratory).
Actually, I published the results 2 years ago however, it seems like a few researchers obtain monocrystalline CeO2 films by the Polymer - Assisted Sol - Gel Deposition method.
Dr. Kenneth M Towe, the reflections are for fluorite CeO2 (the space group Fm-3m). As I know, there are no other polymorphs of CeO2 stable at ambient conditions. However, it is not a mineral, it's a chemical compound.
According to Wikipedia,
"A mineral is a naturally occurring substance that is solid and inorganic representable by a chemical formula, usually abiogenic, and has an ordered atomic structure. It is different from a rock, which can be an aggregate of minerals or non-minerals and does not have a specific chemical composition. The exact definition of a mineral is under debate, especially with respect to the requirement a valid species be abiogenic, and to a lesser extent with regard to it having an ordered atomic structure. The study of minerals is called mineralogy."
"A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions."
I do believe that a chemical compound is more fundamental than a mineral. Basically, a mineral is composed of chemical compounds(doped or pristine). Am I wrong?
http://materials-test3.springer.com/isp/physical-property/docs/ppp_040709
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