Powder X-ray Diffraction

Powder X-ray Diffraction

  • Laxmikant Pathade added an answer:
    Unexpected sharp PXRD peaks for NP sample. Possible explanation? How can I get rid of these very sharp XRD peaks?

    I have a Fe/Cr nanoparticle system with average NP diameter of ~ 10 nm. I have verified NP formation via TEM analysis. However, during the powder X-ray analysis I have been observing extremely sharp peaks at lower 2-theta values (15-35 °). These peaks do not correspond to any metallic or metal oxide standards I’m utilizing. Can someone please explain why these peaks are appearing in my PXRD data? I suspected that organic ligand species might cause this, but that seems unlikely, as I have employed an additional ligand cleaning steps. Thank you for your valuable time.

    Laxmikant Pathade · Syracuse University

    I have identified the source of these sharp peaks as the precursor impurities present in the NP samples. These were removed by solvent-nonsolvent precipitation method. Thanks to Sigurd Olen and Dr. Meetei for your advice and Ravi Anand for your detailed write-up. Dr Coker, we employ a zero diffraction SiO2 substrate, so substrate induced error is unlikely.

    Thank you all for your insightful suggestions and interest in my question. Please let me know if someone has more questions or suggestions.

    Thanks,

    LP

  • Ravi Ananth added an answer:
    Would anyone have a clue as to the origin of "unexpected spots" in the real time 2D XRR signal from thin film samples on substrates?

    X-ray reflectivity (XRR) is a technique abundantly used and vetted, for determining film thicknesses and "flatness" of thin film samples on substrates, over the past century. We have implemented this method in real time using a 2D detector to examine (1) the NIST 2000 SRM (standard reference material) and (2) a sputtered Pt thin film sample on (001) Si substrate.

    The 2D XRR signal was acquired using AXIS25 2D imaging system with spatial resolution of 27.7um, 12.5 fps, 12 Bit dynamic range. The XRR signal using Omega-2Theta scan, shows some interesting persistent "spots" on either side of the "main beam". I'm unable to ascertain the origin of these "unexpected spots" that appear in both cases. We've used the Bruker D8 for the NIST 2000 sample and a Panalytical X'Pert for the Pt. thin film with nearly identical optics and beam conditioners. The incident beam was monochromated to KAlpha 1 only while the KAlpha 2 component was  attenuated!

    Please share your experience and knowledge in XRR to help explain the origin of these "unexpected spots". The angular range (0-0.2o, between the main beam and the total internal reflection angle) is too small for these to be from some diffraction phenomenon such as "slit scattering", isn't it?

    Your helpful suggestions will be deeply appreciated!

    Ravi Ananth · OnSight Technology USA

    And I thought I was imagining these patterns both in real space (topograph x,y, 2-Theta) and in reciprocal space (rocking curve or Omega/Phi/Chi space) for the past 5 years at least. " :-)

    Good news is that I have all the original real time video data from the past 5 years at least. I will analyze all of them again. That'd be fun!

    BTW while you are in the "giving mode" and for the purposes of clarity please share with us:

    • What is the correct interpretation of the term "diffuse scattering" as it is used in XRD today?
    • What is the correct interpretation of the term "rocking curve" as it is used in XRD today? I notice some folks use the term "rocking curve" exclusively for the "Omega only" (decoupled) scan. Is this the convention in the XRD community?

    I notice various interpretations of these terms and want to be unequivocal. 

    Besides synchrotron based investigations of this phenomenon of Yuneda spots/wings/etc., are you aware of any other references based on conventional laboratory based XRD instrumentation in present day literature engaging with this subject? If so, please share.

  • Ravi Ananth added an answer:
    What is the difference in FWHM from Guassian and Lorent fit used in Scherrer formulae?

    I have calculated the crystallite size of NiO by using the well known Scherrer formulae. I fit the XRD peaks and determined the FWHM both by Gaussian and Lorentz fit however the crystallite size calculated by using the FWHM from Lorentz fit is almost double than using the FWHM obtained from Gaussian fit. I used mere FWHM (i.e. 2theta) without making it half and I believe it is the right way of calculation. Could someone help me to know the possible mistakes in getting larger crystallite size value (double) using Lorentz fit? My doubt now is whether I should use half of the FWHM (i.e. 2theta) obtained from Gaussian or Lorentz fitting in calculating crystallite size?

    Ravi Ananth · OnSight Technology USA
    1. The shape of the Bragg profile is dependent on the instrumental profile (from "known standard") which in turn is related to the optics and beam conditioners used. Gaussian will work only if the the incident beam (for example Cu tube) is conditioned by just a Ni filter to attenuate KBeta. So, the reciprocal spot would now appear to be a Voigt or Pseudo Voigt due to the simultaneous presence of K Alpha 1&2 components at lower angles where they sort of overlap due to the integration of XRD signal with the conventional 0D point counter. However, using the Rachinger method to deconvolute K Alpha 1&2 components one can still use Gaussian. Note that the Nano structure of the material itself modulates the Bragg profile and creates asymmetry as well.
    2. If you are using the Scherrer formula then I'd be using the integral breadth (beta) instead of the FWHM as pointed out by Sami.

    Here are some references that may help:

    X-ray Diffraction Fundamentals:

    1.  Bragg's Law and Diffraction: How waves reveal the atomic structure of crystals. http://web.pdx.edu/~pmoeck/phy381/Topic5a-XRD.pdf
    2. Paul Barne, Simon Jacque, Martin Vickers; X-ray diffraction peak shapes – Gaussian, Lorentzian (Cauchi), Pearson VII, Voigt, Pseudo Voigt
    • a. http://pd.chem.ucl.ac.uk/pdnn/peaks/peakcon.htm 
    • b. http://pd.chem.ucl.ac.uk/pdnn/pdindex.htm#peaks 
  • Cesar Cusatis added an answer:
    What are the changes in true unit cell volume when applying a macrostrain model?

    I'm stuck trying to understand the physical meaning of a model in MAUD that seems to describe my data really well. I have data on CeN (in the NaCl structure) in a diamond anvil cell, but the {200} reflections are shifted to lower angle compared to the {111}. Data and refinement without macrostrain is attached.

    Now, I find that using the WSODF model and refining the 230 and 120 coefficients makes the fit about as good as one could hope for (refinement also attached). I just don't really understand the following:

    1. If I calculate the macrostrain under the model options, do I just multiply that onto the three unit cell axes to get the "true" unit cell that I observe?

    2. If I do so, the values I get (a = b = 4.609 Å, c = 4.663 Å) then result in the same unit cell volume as the unstrained case (where a = 4.635 Å). Is this a coincidence?

    3. What is the physical picture of this strain model? It clearly doesn't break the cubic symmetry (the {200} should split if it did), but how does this agree with the strained unit cell parameters above?

    4. Am I overfitting the macrostrain?

    Cheers from a scientist battling with the physical meaning his model (don't we all).

    -------------

    Notes for people who might actually look at the data:

    - The Cu is there on purpose as a pressure standard.

    - There is also some anisotropic broadening going on, with {200} being much narrower than {111}, but that does not confuse me so much. I don't know if I should be able to see a connection to the macrostrain.

    Cesar Cusatis · Universidade Federal do Paraná

    I work with x-ray optics and could not help you with this problem. But I am trying to macrostrain (traction) perfect single silicon crystals by pulling and measuring in situ with double crystal X-ray diffraction the variation of lattice parameter. I have strong doubts on how to do it and maybe you could help me with that. If so, please, send me your email address. My address is cusatis@fisica.ufpr.br. Thank you in advance.

  • U. Chinna Rajesh added an answer:
    Can anybody help me to solve the powder XRD of MNPs which were synthesized by hydrothermal method? (attached XRD spectra)

    I have prepared MNPs (expected CuFe2O4) from aq. solutions of FeCl3 (1 eq) and CuCl2 (0.5 eq), urea (10 eq), glucose (10 mol%), and 30% aq NH3 (10 mL), ethgylene glycol (10 mL) by hydrothermal  method at 180 oC, for 8h. There are two possibilities to form either carbon coated CuFe2O4 or CuO/Carbon/Fe3O4 NPs.

    The mechanism for formation of CuO/Carbon/Fe3O4 might be as follows: The glucose can reduce Fe(III) to Fe(II) to form carbon coated Fe3O4 followed by stabilization of insitue generated CuO from CuCl2 in presence of basic medium (aq. NH3).

    or Carbon coated CuFe2O4 can form from the reaction among FeCl3, CuCl2, glucose in presence of basic medium.

    Please help me to solve PXRD (attached) of this material.

    Thanks in advance

    U. Chinna Rajesh · University of Delhi

    Hi Maykel,

    I am really glad to see XRD analysis of my sample. I agree with you, it is Hematite.

    Thank you very much.

  • Gheorghe Branoiu added an answer:
    How can I improve the peak shape fitting in Rietveld refinements using TOPAS software?

    The data was collected on powder XRD (Bruker) with 0.02/2s scan, Ka2 and probably some Kb are there.

    I am currently getting Rexp = 2.766 Rwp= 12.327, GOF = 4.723. This is the result after anisotropic refinement (in Launch mode) is performed. I think, by looking at the graphic of the fit, that peak shape and broadening seem to be the main problem?. Is there anything I can do to improve this? So far I have refined the basic parameters and structure-related parameters. The sample is 30%doped of the parent compound but the pattern looks really really similar so I use the model of the parent compound. The doping ion is Bi3+ and having lone pair electrons and being quite lager might cause much strain, could this be the reason?

    Gheorghe Branoiu · Petroleum - Gas University of Ploiesti

    It's true that your new Rwp value of  9.737 is better than the previous (12.327), but your refinement could be improved further. This is shows by the difference between observed and calculated X-ray diffraction patterns.

    And your figure of merit GOF 3.736 is far away ........... Your Rwp value it must closer to Rexp. (see Luca Luterotti - Rietveld training: http://www.xray.cz/xray/csca/kol2011/kurs/Dalsi-cteni/Luca-Lutterotii-Rietveld.pdf ).

    What is the value of DW?

    Try to made some corrections. Check the emission profile or the order of Chebychev polynoms or zero point error, LP-polarization factor. Also be aware to the X-ray absorption. Preferred orientation you already corrected. 

    Maybe is necessary a new scan: your collected data with 0.02/2s scan can be a little bit inaccurate. Try to increase measurement time. I recommend 0.01/5s or 0.01/10 s and continuous mode. 

    What type of Bruker diffractometer do you have?

    Good luck!

  • Karim Khan added an answer:
    XRD software
    What is the best free software for the analysis of powder-XRD data?
    I have .raw and .doc(X-Y) data.
    Karim Khan · Ningbo Institute of Materials Technology and Engineering

    can we refine our XRD data by using JADE-software ?

  • O. B. Korneta added an answer:
    What free software do you use to analyze XRD data?
    There is many free software to analyze XRD data but what is the best, if I have raw, dat, cpi, sd , rd data?
  • Anil Gaikwad added an answer:
    How do I calculate the porosity of thin films by using XRD?

    More specifically I am interested to calculate porosity of silica aerogel thin films.

    Anil Gaikwad · North Maharashtra University, Jalgaon MS India

    Thank you all for your valuable guidance .

  • K. Vijai Anand added an answer:
    What are all possible reasons for the peak shift in X-Ray Diffraction?

    Hello everyone! 
    I have successfully synthesis my nanocomposites but as i increase the concentration of Dopant material there is a peak shift in XRD. So anyone tell me all possible reasons for this?
    Thank you in advance!

    K. Vijai Anand · Sathyabama University

    The shift may be due to the difference in the ionic radii of the main element and the dopant.

  • Ashok Bhakar added an answer:
    How can I calculate accurate ATZ values for Fullprof program of same ABO3 (PbMg1/3Nb2/3O3) compound with two different space groups (Pm-3m & R3m)?

    In multiphase phase refinement % of phases depends on ATZ value. What are the ATZ value for Pm-3m phase of PbMg1/3Nb2/3O3(ATZ calculated by Fullprof=325.25) & for R3m phase of PbMg1/3Nb2/3O3 (ATZ calculated by Fullprof= 108.43). Are ATZ values calculated automatically by Fullprof program correct?

    ATZ definition from Page 91 of fullprof manual

    ATZ – Quantitative phase analysis
    Coefficient to calculate the weight percentage of the phase.
    ATZ = Z MW f2 / t
    Z: Number of formula units per cell, Mw= molecular weight
    f: Used to transform the site multiplicities used on line 1 1 -41 to their true values. For a stoichiometric phase f=1 if these multiplicities are calculated by dividing the Wyckoff multiplicity m of the site by the general multiplicity M. Otherwise f=Occ.M/m, where Occ. is the occupation number given in LINE 25.
    t: Is the Brindley coefficient that accounts for microabsorption effects. It is required for quantitative phase analysis only. When different phases have similar absorption (in most neutron uses), this factor is nearly 1 (in such case ATZ=Z MW f2 ). The Brindley coefficient is directly read in one of the following lines. 

    Definition of Occ on Page 102

    Occ - Occupation number


    Occupation number i.e. chemical occupancy × site multiplicity (can be normalised to the multiplicity of the general position of the group)

    Atomic positions provided in .pcr file for two space groups along with Occupancy (bold & italic) are given below:

    P m -3 m <--Space group symbol (Phase 1 ATZ from .out file = 325.25)

    !Atom Typ X Y Z Biso                   Occ In Fin N_t Spc /Codes

    Pb PB+2 0.00000 0.00000 0.00000 4.51975          0.02083 0 0 0 0

    Mg MG+2 0.50000 0.50000 0.50000 1.25171        0.00694 0 0 0 0

    Nb NB+5 0.50000 0.50000 0.50000 1.25171         0.01389 0 0 0 0

    O O-2 0.50000 0.50000 0.00000 2.59967              0.06250 0 0 0 0


    Phase 2: R 3 m with Hexagonal axis (ATZ from .out file = 108.43)

    R 3 m <--Space group symbol

    !Atom Typ X Y Z Biso          Occ In Fin N_t Spc /Codes

    Pb PB+2 0.00000 0.00000 -0.02811 2.77707           0.05556 0 0 0 0

    Mg MG+2 0.00000 0.00000 0.50000 0.53938           0.01852 0 0 0 0

    Nb NB+5 0.00000 0.00000 0.50000 0.53938            0.03704 0 0 0 0

    O O-2 0.16667 -0.16667 0.3333 2.00000                 0.16667 0 0 0 0

    Ashok Bhakar · Raja Ramanna Centre for Advanced Technology

    Dear Maykel Manawan and Yazan Maswadeh, thanks for your support.

  • Zdenek Pala added an answer:
    Comparing the XRD patterns of mixtures containing CaCO3, how can I just roughly prove that one sample contains more aragonite than another one?

    I have the XRD patterns of two samples which mainly contains calcite and aragonite (S1 and S2, see the attachments). How can I just roughly say that S2 has more amount of aragonite than S1?

    Zdenek Pala · Academy of Sciences of the Czech Republic

    Felix is absolutely right, do quantitative Rietveld with profile refinement and you have immediately the answer you want. 

  • Zdenek Pala added an answer:
    I want to measure the residual stress in a solid sample. Is it possibile, without the internal standard?

    Is possible to measure  stress by XRD, on powder?

    Zdenek Pala · Academy of Sciences of the Czech Republic

    Why would you measure residual stress on powder? Firstly, do you speak about macroscopic (or the 1st order) or microscopic (2nd order) or even submicroscopic (3rd order) residual stresses? For the macroscopic RS, you can fully characterize them by 2nd order symmetrical tensor, which is reasonable for example for ground, milled or in general anisotropically surface treated objects. But for powder, there could of course be some macroscopic residual stresses, but how will you find the reference coordinates? Nevertheless, you can load your powder into a proper sample holder (preferably by a side loading technique) and try to measure a suitably chosen high angle profile under several tilts. I would expect equi-biaxial stress state if any (for biaxial stress state you don't really need to know the d0 stress-free value)....In powders, you probably usually want to determine microstresses and that is usually done by profile analysis and using Rietveld refinement....

  • Arun Pandian Chandrasekaran added an answer:
    How can I calculate crystallinity index (CI) from XRD data?

    I have seen some methods in web but it seems to be difficult. I am a beginner to this kind of work. Any suggestions from your side would be very helpful. Thanks in advance. 

    Arun Pandian Chandrasekaran · Kumaraguru College of Technology

    Thank you for your answer. I'll check it out. 

  • Faria Naqvi added an answer:
    In XRD why is 2-theta used, instead of theta?
    .
    Faria Naqvi · Aligarh Muslim University

    This is all due to Bragg's equation. The incident ray and reflected ray all making the angle theta with a crystal plane.Reflections from planes set at  theta  angle with respect to the incident beam generates a reflected beam at an angle 2-theta from the incident beam.

  • Daniel Robert Cluff added an answer:
    What is the importance of atomic displacement parameters (U) in GSAS?

    Hello I am doing a quantatative rietveld refinement on Ni, Ti and its intermetallics. In order to get reasonably accurate data I need some solid U or B values. I have found some data with respect to HCP Ti and Ni and compared it to my refinements. The Ni is close but the Ti is sitting at .0102 (refined from my data) instead of 0.006 (from literature). It only changes my results by 2 % (i.e. Ti is 52 wt% with the former and 50 wt% witht the latter). I have runs where there is a significant amount of each intermetallic on which I can refine to get Uiso values but they so far are really high.

    I guess a few clear questions are in order:

    1) how much variation in Uiso is acceptable

    2) what are acceptable values of Uiso for metals and intermetallics at room temperature and at high temperatures? (I am going up to 1473K)

    3) Is it preferable to use the experimentally determined values over the given that due to the nature of my experiment it is not an ideal powder diffraction experiment. ( I have sintered in situ so I have a solid polycrystalline piece -not a powder- that could have some texture).

    Sorry for the long question. I welcome any thoughts even if they only address one of the questions.

    Dan 

    Daniel Robert Cluff · Dalhousie University

    My main goal is phase fraction. I am sintering in situ, in other words I am doing neutron diffraction while my specimens are sintering. During sintering I go from the two elemental phases to ideally a singular NiTi phase but in between I get all the phases as you would expect based on the phase diagram. These phases appear and disappear. My goal is to track the changes with time and changing temperature. What I am after is the most accurate phase fractions I can get and not necessarily a refinement of the structure (although I clearly need an accurate idea of what my structure is if I am to get accurate phase fractions).

    Given the problems getting a Uiso from the data I am worried that if I get one that is too small it throws off the phase fraction values. The same can be said if it goes too high. So what I am looking for is how do I make sure I get phase fraction data I can trust (given that it is for sequential patterns, i.e. I am watching the phases appear and disappear over time) I do not need to know the phase fraction down to 1% if my errors are of the order of 4 % I can handle that as I will have a phase fraction value on each side of that point to determine if it fits the trend or if it is an outlier.

    Also I have some runs where I have relatively pure phases (or almost singular where the phase id >93 %). But given that I am only going to 95° the values I am getting do always match the literature (it does not help I an having trouble finding values in the literature for 1473 K). I have been refining everything with my best guess Uiso values based on some of those high phase fraction runs and then letting the Uiso refine at the end (only for phases that have sufficient phase fraction to allow it). I am just not sure this is the correct and/or the best way I can do it.

    Not sure that is clear, if not let me know and I will try to clear it up a bit more

  • Ravi Ananth added an answer:
    How can I calculate crystallinity from XRD?

    This is my first time dealing with XRD and I would like to calculate the crystallinity of my sample using powder XRD, I was trying to use the segals equation but I am not sure if its the right one for my sample, particularly because my peaks are not in the 2Theta region usually used for this equation, wherein max intensity peak is between 22-24 degrees and the amorph is taken at an angle of about 18 degrees  in the valley between the peaks.

    The sample is cellulose which initially had peaks in the regions mentioned above ,however, after regeneration the peaks shifted, crystalline at around 13 degrees and amorph at around 18 degrees. Just to see I calculated the crystallinity using the Segals equation but the values are way too high for regenerated cellulose indicating that this is probably not the right way to do it 

    The XRD graph is attached (sample holder was glass, which is why theres quite a bit of noise). Can someone please advice how else I can calculated the crystallinity from the XRD. 

    Ravi Ananth · OnSight Technology USA

     "Amorphous phases cannot be detected directly by X-ray diffraction analysis". Only if you are handicapped by conventional XRD tools and techniques :-)

    However, Maykel is right in the sense that precise quantification of a mixture of amorphous and crystalline phases is not a trivial task (may be impossible) with a conventional equatorial diffractogram that your are presently using. Having said that, it is quite common practice to estimate the relative amounts of such phases in samples using carefully created "known standards" when possible. It would also require careful and consistent sample preparation in this case. There are many more factors that may cause errors such as diffractometer alignment and sample surface alignment co-linear with the diffractometer axis (see attached RG discussion). Besides, amorphous/crystalline phase combination would invariably be accompanied with the ubiquitous "preferred orientation" monster :-). See attached image with Aluminum foil and Kevlar fibers.

    For the time being just run and compare the diffractograms for various samples. Post the data. You may subsequently be able to compute integrated intensities below constituent peaks after identifying them and fitting them with the correct profile. This may be accomplished using many of the existing software. What XRD equipment are you employing? Please post details.

    "Subtract" is a word I'd avoid in XRD. The better euphemism is "deconvolute" after unequivocal identification.

    "how to improve the signal to noise ratio?". An excellent and practical question. Quick answer is, try a zero background sample holder (Si mono-crystal)! The full answer would depend on several of these enumerated factors:

    1. What XRD instrumentation are you using? Please share details.
    2. What beam conditioning apparatus are you utilizing? Fliters, monochromators, collimators, slits, diffractometer radius, etc.
    3. What tube/source are you using?
    4. What is the chemistry of the sample?

    P.S.: Please include additional relevant topics (up to 15) up top for enhanced circulation and improved feedback. Review the attached RG discussion regarding diffractometer alignment for a variety of such topics.

  • Karar Abdali added an answer:
    Is XRD applicable for particles less than 4 nm?

    A paper published in science mentioned; "Samples did not show the characteristic diffraction lines from iron oxide, indicating that the Fe2O3 was amorphous or that the crystallites were smaller than 4 nm". Does it mean that if particle size is less than 4 nm we will not get XRD pattern? Can anyone help me clear the confusion?

    Karar Abdali · University of Babylon

    Dear, XRD suitable.

  • M. BENDOUMIA added an answer:
    Is anyone familiar with XRD at high temperature?

    When using a high temperature XRD analysis. We heated with a predetermined rate to the desired temperature, where we realized an analysis: at that moment does we continues to heat during the recording or we maintains the temperature.

    Is there anyone who can explain me the process of high temperature XRD analysis.

    Thank you very much 

    M. BENDOUMIA · University of Science and Technology Houari Boumediene

    we have a diffractometer equipped with a Pixcel 1D detector, and i don’t know if it's faster than the SPD detector, and if it's more recommend for a no ambient XRD.

  • Ingy Nagy Ghoniem added an answer:
    Are you familiar with the XRD spectrum for graphene?

    Can anyone tell me which 2theta values xrd peaks can be found for pure graphene ?

    Ingy Nagy Ghoniem · Egypt-Japan University of Science and Technology

    it can be done easily if you compared your graphene xrd spectra with the GO xrd curve .. not to forget to take into consideration the method of graphene production .. 

  • Sharang Rs added an answer:
    Can we deduce phase of the sample using lattice parameters with EBSD ? Can we measure the change in lattice parameters of a phase with EBSD ?

    While doing some measurements involving change in phase of silver due to oxidation or another likely transformation into Ag3N in EBSD, it was observed that the lattice parameters of the oxide and nitride phases were almost the same and on replacing one with the other in measurement, it did not create a discernable change in its result. Measurements were performed with Bruker EBSD camera. Is it likely that software requires upgrading or lacks the function to identify the correct phase ? Or EBSD in itself is incapable of phase identification ?

    Sharang Rs · Fachhochschule Jena

    I thank you both on your replies. i will start working towards understanding the implications of your suggestions and would post about the consequent results.

  • Paul Barnes added an answer:
    How instrument resolution (good/poor) affect the size/strain information (even after removing the Instrument resolution)?

    Suppose there are two XRD instruments with resolution/FWHM (A) 0.030 & (B) 0.30 @ two theta ~ 350 (assume these Instrument FWHM are calculated by measuring same NIST SRM powder at two instruments in range10-1400). Also Instrument resolution file (IRF) are made using FullProf software  in 2 theta range 10-1400.

    Now a nano-crystallite ~50nm (or strained material) powder XRD performed at both instruments A & B and contribution of respective Instrument (IRF's) are subtracted.

    Then measurements with two instruments (A & B) give

    (1) size or strain value comparable but not equal? if yes, how?

    (2) size or strain value obtained in two cases EQUAL after removing instrument resolution? If yes, how?

    (3)  If size or strain value obtained in two cases differ significantly, then which one give better result compared to other (although respective instrument contribution is removed from both cases)? Why?

    (4) Other options?

    Paul Barnes · University College London

    My thoughts exactly mirror those of Alexander B. Missyul.  Its all to do with the

    differences, small or large, between numbers, small or large. 

  • Yousef Alsabah added an answer:
    What is the effect of doping of nitrogen on the TiO2 powder in the XRD pattern?

    What is the difference between TiO2 and N-doped TiO2?

    Yousef Alsabah · Al-Neelain University

    i think no big deffect but the analysis is the govern

  • José M. Amigó added an answer:
    How can I get the percent of crystallinity from Powder XRD data?
    I have done XRD and having data file and drawn xrd patterns using Powder X software. I need % crystallinity.
    José M. Amigó · University of Valencia

    Since the early twentieth century diffraction (ICDD) are characteristic of crystalline solids.
    Quantitative analysis by XRD of the phases present in a polycrystalline material is based on the principle that a phase integrated intensities are related to their abundance in the mixture (Klugg & Alexander, 1974).
    Through various programs Rietveld can quantitatively analyze the crystalline phases. Absolute weight percentages of each of the phases is 100%. If amorphous phase or unidentified crystalline impurities are present in the sample, these percentages can be determined by adding a known amount (e.g., around 20% by) of an internal standard.
    The difference between 100% and the total of absolute abundances represent the amount of glassy phase.

  • Jason Potticary added an answer:
    Why would cooling a polycrystalline material down cause differences in peak intensity in powder XRD?

    I have run a sample at various temperatures with out removing / rotating the sample or changing the diffractometer, it was locked in the machine the whole time. There are definitely  diffrences in peak intensity that are monotonic with temperature and reversible...I'm not sure how to explain it.

    Any ideas?

    Jason Potticary · University of Bristol

    Hi all, and thanks for your answers. To fill in some blanks: My sample is an organic crystal and when I say 'intensity' I only mean relative, integrated intensity. I've included my data table (sorry for the shoddy construction but it's just a quick port from latex) which should be readable.

    I was hoping there would be a simple generic consensus about what would be causing it, which I was scarce with the details...should have known that science doesn't work that way!

  • Abdullah Sert added an answer:
    How can I conduct phase identification and quantification of a solid solution of 0.6 wt % silicon in tungsten carbide - cobalt composite by XRD?

    I am trying to characterize a cemented tungsten carbide composite with cobalt binder, doped with 0.6 wt.% of silicon by X ray diffraction. The silicon is not detectable because of its low concentration and is completely dispersed in the cobalt. Could anyone give me ideas on any other techniques to use (such as EBSD) or if sample tilting would work?

  • Kunyapat Thummavichai added an answer:
    How can I index rings in electron diffraction pattern from TEM for a sample mixture of different phases?
    I have SAED pattern for my sample which is Zn-Ni coating. Based on XRD results, it is a mixture of pure Zn and some intermetallic Zn-Ni phases. How can I index rings? The attachment is SAED of my sample. I wanted to try using equation Rd=lambda*L to calculate d spacing, but found it too complicated for a sample, having a mixture of several phases.
    Kunyapat Thummavichai · University of Exeter

    pixel size for my image= 15 micron/ (0.0025 nm * 200mm)= 0.03 (1/nm)

    i am abit confuse of this calculated , could you explain more about it ?

  • Marcella Bini added an answer:
    How can I analyse a new powder XRD data for new composition?

    We prepared and recorded powder XRD data for one new system. we checked the phase confirmation with JCPDF - ICDD data. But we did not get the data. I think this is new compound which is not reported earlier by any authour. Kindly suggest me how to solve this data and confirm the phase formation for new system. i tried this data for the confirmation of phase formation in rietvield method and full proof programme. Unfortunately i did not get the answer. Kindly give me suggestions to solve this problem.

    Marcella Bini · University of Pavia

    Did you checked the chemical composition of your material? Do you tried to search for reagents or other different combinations of the atoms present in your stoichiometric mixture? In fact before starting with the procedure of ab initio determination of a new Crystal structure I suggest you to be certain to have a new structure

  • Natheer Basheer Mahmood added an answer:
    Is there any website where I can find 2theta(/theta) values for peaks generated by minerals?

    Is there any website where I can find 2theta(/theta) values for peaks generated by minerals? Given that the sample mineral composition is not well known.

    Thank you

    Natheer Basheer Mahmood · Al-Nahrain University

    You can use Crystallography open database for this purpose

    http://www.crystallography.net/

    and using crystal impact diamond for opening the CIF file

Topic Followers (758) See all