Re: Amorphous content
We have positive experience with commercial ZnO pigments or chemicals, heated to 700°C for about 2 hours in air for recrystallisation of the amorphous ZnO or the spurious Zn carbonates/hydrates to get nearly 100% crystalline ZnO. In 1:1 mixtures of the best NIST corundum, we found no significant deviation in Rietveld quantification, and so we use it routineously as internal standard. Such ZnO shows separate particles of about 0.5 µm diameter what can be assumed to persist a grinding and allow an appropriate low phase-specific correction for microabsorption. As Pamela stated, in case of the CeO2 one problem may be the absorption contrast between the materials. The problem can only minimised by (a) choosing an appropriate wavelength (as Pamela recommended Mo?), and/or (b) optimising/minimising the effect of the PARTICLE size of all constituents of the mixture. Thus, it is recommended to grind as fine as possible and then to look for the resulting particle size of the powder (e.g. by laser scattering). The particle size should at least fulfill the conditions of µ*D to be fine or medium given in Brindley, G.W. 1945. The effect of grain or particle size on X-ray reflections from mixed powders and alloys considered in relation to the quantitative determination of crystalline substances by X-ray methods, Phil. Mag., Ser. 7, 36: 347-369. In general, a correct mean particle size of the phases should used in the Brindley correction term. In our experience, the mixing of the standard ZnO and the sample powders can cause problems like forming aggregates of the both materials. For example, if larger aggregates of ZnO persist in the sample one can get negative amorphous content because of the underestimation of the ZnO by microabsorption. In contrast, coarse aggragates of sample phases cause underestimation of these crystalline phases and result in pseudo-amorphous contents. Therefore we prefer admixing of the standard before grinding the sample to reach a really homogeneous mixture, assume the 0.5 µm particle size for Brindley correction of the scale factor of ZnO, and set an estimated particle size (mostly 1-4 µm) globally for the phases of the powdered sample, according to some experience regarding hardness and behaviour of the material in our mill. However, the uncertainty of this estimated values can still significantly bias the result of quantification of the amorphous content, especially for heavily absorbing materials. This can simply checked by calculating the Brindley correction factors for linear absorption coefficients of the actual sample material and varying the particle size in a realistic interval. Reinhard Kleeberg Whitfield, Pamela schrieb: At first glance it looks like a classic microabsorption problem, but I don’t have the linear absorption coefficients to hand. Using an internal standard with a too small absorption will tend to over-estimate the amorphous content. Ce versus Zn is a pretty big contrast for CuKa, even if the particle sizes are small enough. The whole point of that NIST series (674 I think) is that they were to be used as appropriate contrast matching standards for quant analysis, and were supposed to be quite different from each other. Changing the wavelength to reduce the contrast (e.g. Mo) may help for that particular mix but probably won’t completely solve it. Pam *From:* Peter Y. Zavalij [mailto:[EMAIL PROTECTED] *Sent:* November 15, 2007 9:07 PM *To:* rietveld_l@ill.fr *Subject:* Amorphous content Hi, I am trying to determine amorphous content using Rietveld refinement and internal standard. However resulting content of amorphous phase is really unrealistic. Moreover testing the method using standards with known amorphous content does not clarify the situation. For example ZnO (NIST, 95% crystallinity) used as standard to determine amorphous content in CeO2 (also NIST standard with 91% crystallinity) yield 25% of amorphous phase which is a little bit too much comparing with expected 9%. We tested several different standards, mixtures and preparations, different diffractometers and software without much luck... Seems like something simple is missing... Any clues? Many thanks, Peter Zavalij X-ray Crystallographic Laboratory Department of Chemistry Biochemistry 091 Chemistry Building University of Maryland College Park, MD 20742-4454 Phone: (301)405-1861 Fax: (301)314-9121 E-mail: [EMAIL PROTECTED] http://www.chem.umd.edu/facility/xray/
Re: Sources of standard reference materials
Hi! You can try with ZnO, annealed at 950ºC, 72 h h, ( from works of Langford and Louêr) best wishes Miguel Hesiquio Hi All, Does anyone know an appropriate source of standard reference materials for a line profile standard, like NIST SRM 660a (LaB6) - other than NIST, as they are out of stock and ...is expected to become available by November 2009. Thanks, Ross Miguel Hesiquio-Garduño Profesor Titular A Departamento de Ciencia de Materiales Academia de Ciencias de la Ingeniería ESFM-IPN. tel 57 29 60 00 ext. 55003, ext. 55011
RE: Amorphous content
Thanks Reinhard and all for quick and comprehensive answers. It appears that we do have microabsorption effect as Rietveld content deviates from expected in accordance with absorption coefficients and there is no simple fix for that but take proper precautions in sample preparation and select right reference material. Best regards, Peter Zavalij BTW does anyone has electronic copy of Brindley paper? X-ray Crystallographic Center Department of Chemistry Biochemistry 091 Chemistry Building University of Maryland College Park, MD 20742-4454 Phone: (301)405-1861 Fax: (301)314-9121 E-mail: [EMAIL PROTECTED] http://www.chem.umd.edu/facility/xray/ -Original Message- From: Reinhard Kleeberg [mailto:[EMAIL PROTECTED] Sent: Friday, November 16, 2007 3:14 AM To: rietveld_l@ill.fr Subject: Re: Amorphous content We have positive experience with commercial ZnO pigments or chemicals, heated to 700°C for about 2 hours in air for recrystallisation of the amorphous ZnO or the spurious Zn carbonates/hydrates to get nearly 100% crystalline ZnO. In 1:1 mixtures of the best NIST corundum, we found no significant deviation in Rietveld quantification, and so we use it routineously as internal standard. Such ZnO shows separate particles of about 0.5 µm diameter what can be assumed to persist a grinding and allow an appropriate low phase-specific correction for microabsorption. As Pamela stated, in case of the CeO2 one problem may be the absorption contrast between the materials. The problem can only minimised by (a) choosing an appropriate wavelength (as Pamela recommended Mo?), and/or (b) optimising/minimising the effect of the PARTICLE size of all constituents of the mixture. Thus, it is recommended to grind as fine as possible and then to look for the resulting particle size of the powder (e.g. by laser scattering). The particle size should at least fulfill the conditions of µ*D to be fine or medium given in Brindley, G.W. 1945. The effect of grain or particle size on X-ray reflections from mixed powders and alloys considered in relation to the quantitative determination of crystalline substances by X-ray methods, Phil. Mag., Ser. 7, 36: 347-369. In general, a correct mean particle size of the phases should used in the Brindley correction term. In our experience, the mixing of the standard ZnO and the sample powders can cause problems like forming aggregates of the both materials. For example, if larger aggregates of ZnO persist in the sample one can get negative amorphous content because of the underestimation of the ZnO by microabsorption. In contrast, coarse aggragates of sample phases cause underestimation of these crystalline phases and result in pseudo-amorphous contents. Therefore we prefer admixing of the standard before grinding the sample to reach a really homogeneous mixture, assume the 0.5 µm particle size for Brindley correction of the scale factor of ZnO, and set an estimated particle size (mostly 1-4 µm) globally for the phases of the powdered sample, according to some experience regarding hardness and behaviour of the material in our mill. However, the uncertainty of this estimated values can still significantly bias the result of quantification of the amorphous content, especially for heavily absorbing materials. This can simply checked by calculating the Brindley correction factors for linear absorption coefficients of the actual sample material and varying the particle size in a realistic interval. Reinhard Kleeberg Whitfield, Pamela schrieb: At first glance it looks like a classic microabsorption problem, but I don’t have the linear absorption coefficients to hand. Using an internal standard with a too small absorption will tend to over-estimate the amorphous content. Ce versus Zn is a pretty big contrast for CuKa, even if the particle sizes are small enough. The whole point of that NIST series (674 I think) is that they were to be used as appropriate contrast matching standards for quant analysis, and were supposed to be quite different from each other. Changing the wavelength to reduce the contrast (e.g. Mo) may help for that particular mix but probably won’t completely solve it. Pam *From:* Peter Y. Zavalij [mailto:[EMAIL PROTECTED] *Sent:* November 15, 2007 9:07 PM *To:* rietveld_l@ill.fr *Subject:* Amorphous content Hi, I am trying to determine amorphous content using Rietveld refinement and internal standard. However resulting content of amorphous phase is really unrealistic. Moreover testing the method using standards with known amorphous content does not clarify the situation. For example ZnO (NIST, 95% crystallinity) used as standard to determine amorphous content in CeO2 (also NIST standard with 91% crystallinity) yield 25% of amorphous phase which is a little bit too much comparing with expected 9%. We tested several different standards, mixtures and preparations, different diffractometers and software without much luck...
RE: Sources of standard reference materials
Ross, The link to The Gem Dugout X-ray Diffraction Products is http://www.thegemdugout.com/products.html. The provide several reference specimens for affordable price, e.g. LaB6 - $10/g. And other diffraction products. Peter Dr. Peter Y. Zavalij Director, X-ray Crystallographic Laboratory Department of Chemistry Biochemistry 091 Chemistry Building University of Maryland College Park, MD 20742-4454 Phone: (301)405-1861 Fax: (301)314-9121 E-mail: [EMAIL PROTECTED] http://www.chem.umd.edu/facility/xray/ -Original Message- From: Ross Williams [mailto:[EMAIL PROTECTED] Sent: Thursday, November 15, 2007 9:51 PM To: rietveld_l@ill.fr Subject: Sources of standard reference materials Hi All, Does anyone know an appropriate source of standard reference materials for a line profile standard, like NIST SRM 660a (LaB6) - other than NIST, as they are out of stock and ...is expected to become available by November 2009. Thanks, Ross
Re: Sources of standard reference materials
Hi all, We expect to have SRMs 640d 660b available by no later then November 2008. SRM 676a will available in a ~month. I regret the difficulty that is being caused by this lapse; we are taking measures to prevent them from recurring. Regards, Jim At 09:50 PM 11/15/2007, you wrote: Hi All, Does anyone know an appropriate source of standard reference materials for a line profile standard, like NIST SRM 660a (LaB6) - other than NIST, as they are out of stock and ...is expected to become available by November 2009. Thanks, Ross James P. Cline Ceramics Division National Institute of Standards and Technology 100 Bureau Dr. stop 8520 [ B113 / Bldg 217 ] Gaithersburg, MD 20899-8523USA [EMAIL PROTECTED] (301) 975 5793 FAX (301) 975 5334
RE: Amorphous content
For quantitative analysis the flat-plate transmission geometry is much more preferable as it is free of the microadsorbtion problem. Of course, resolution is not so easily achievable in this geometry, but one may use synchrotron at last. Best regards, Leonid Solovyov Thanks Reinhard and all for quick and comprehensive answers. It appears that we do have microabsorption effect as Rietveld content deviates from expected in accordance with absorption coefficients and there is no simple fix for that but take proper precautions in sample preparation and select right reference material. Best regards, Peter Zavalij BTW does anyone has electronic copy of Brindley paper? X-ray Crystallographic Center Department of Chemistry Biochemistry 091 Chemistry Building University of Maryland College Park, MD 20742-4454 Phone: (301)405-1861 Fax: (301)314-9121 E-mail: [EMAIL PROTECTED] http://www.chem.umd.edu/facility/xray/ Be a better sports nut! Let your teams follow you with Yahoo Mobile. Try it now. http://mobile.yahoo.com/sports;_ylt=At9_qDKvtAbMuh1G1SQtBI7ntAcJ
RE: Amorphous content
Flat-plate transmission? Is this a good example of an oxymoron or am I missing a trick here? Shome mishtake shurely. Martin Vickers Subject: RE: Amorphous content Date: Fri, 16 Nov 2007 06:33:49 -0800 From: [EMAIL PROTECTED] To: rietveld_l@ill.fr For quantitative analysis the flat-plate transmission geometry is much more preferable as it is free of the microadsorbtion problem. Of course, resolution is not so easily achievable in this geometry, but one may use synchrotron at last. Best regards, Leonid Solovyov Thanks Reinhard and all for quick and comprehensive answers. It appears that we do have microabsorption effect as Rietveld content deviates from expected in accordance with absorption coefficients and there is no simple fix for that but take proper precautions in sample preparation and select right reference material. Best regards, Peter Zavalij BTW does anyone has electronic copy of Brindley paper? X-ray Crystallographic Center Department of Chemistry Biochemistry 091 Chemistry Building University of Maryland College Park, MD 20742-4454 Phone: (301)405-1861 Fax: (301)314-9121 E-mail: [EMAIL PROTECTED] http://www.chem.umd.edu/facility/xray/ Be a better sports nut! Let your teams follow you with Yahoo Mobile. Try it now. http://mobile.yahoo.com/sports;_ylt=At9_qDKvtAbMuh1G1SQtBI7ntAcJ _ 100’s of Music vouchers to be won with MSN Music https://www.musicmashup.co.uk
RE: High temperature PXRD fitting in TOPAS
Dear shishir, You probably would like to take a look a the following (open access) paper published last February in Journal of Applied Crystallography: http://journals.iucr.org/j/issues/2007/01/00/issconts.html Hope this helps. Leo Dr. Leopoldo Suescun Postodoctoral Appointee Materials Science Division - Bldg 223 - Rm D217 Argonne National Laboratory 9700 S. Cass Ave., Argonne, IL 60439 Phone: 1 (630) 252 9760 Fax: 1 (630) 252 URL: http://www.msd.anl.gov/groups/nxrs/personnel/suescun/index.html _ From: sisir ray [mailto:[EMAIL PROTECTED] Sent: Thursday, November 15, 2007 7:22 PM To: rietveld_l@ill.fr Subject: High temperature PXRD fitting in TOPAS Hi, I have got high temperature Powder xrd data (from lab xray source) in the range of 30 ~1000 C . But i am not sure how to fit them correctly in TOPAS as i dont know where to put the temperature information. Any kind of suggestion is really appriciated. -- thankyou, regards shishir BEGIN:VCARD VERSION:2.1 N:Suescun;Leopoldo FN:Leopoldo Suescun ([EMAIL PROTECTED]) ORG:Argonne National Laboratory - Materials Science Division TITLE:Postdoctoral Appointee TEL;WORK;VOICE:+1 (630) 252-9760 TEL;HOME;VOICE:+1 (630) 910-1562 TEL;WORK;FAX:+1 (630) 252- ADR;WORK:;;9700 S. Cass Ave.;Argonne;Illinois;60439;USA LABEL;WORK;ENCODING=QUOTED-PRINTABLE:9700 S. Cass Ave.=0D=0AArgonne, Illinois 60439=0D=0AUSA URL;WORK:http://www.msd.anl.gov/groups/nxrs/people/suescun.html EMAIL;PREF;INTERNET:[EMAIL PROTECTED] REV:20050630T182807Z END:VCARD
Kapton capillaries
Could someone please suggest a source for purchasing kapton capillaries? A search on the internet drew a blank. Thanks. Dipo Omotoso
Re: Kapton capillaries
Could someone please suggest a source for purchasing kapton capillaries? A search on the internet drew a blank. Try polyimide rather than kapton. We have used MicroLumen as a vendor: http://www.microlumen.com/ Brian
Re: Kapton capillaries
We use thin-walled heat shrink PET tubing from advanced polymers. Fewer peaks in the low angle region and it comes in a colorless/ clear form. Joe Reibenspies Brian H. Toby wrote: Could someone please suggest a source for purchasing kapton capillaries? A search on the internet drew a blank. Try polyimide rather than kapton. We have used MicroLumen as a vendor: http://www.microlumen.com/ Brian -- Joseph H. Reibenspies Ph.D. Department of Chemistry Texas A M University College Station, Texas [EMAIL PROTECTED] www.chem.tamu.edu/xray (979)845-9125
Re: Sources of standard reference materials
Dear Ross, We are working in the preparation of standard materials for XPD equipment alignment / calibration and also for obtaining instrumental breadth for line profile analysis (Rietveld, Warren-Averbach etc.). In our opinion a simple and good choice is high purity ytria (Y2O3) treated at 1200º C for 72 h followed by grinding and sieving (= 5 micron ?m). Regards, Luis -- Dr. Luis Gallego Martinez Comissão Nacional de Energia Nuclear Instituto de Pesquisas Energéticas e Nucleares Centro de Ciência e Tecnologia de Materiais Av. Prof. Lineu Prestes 2242 Cidade Universitária - USP São Paulo - SP - Brasil - CEP:05508-000 Tel: + 55 11 3133-9222 Fax: 3133-9276 [EMAIL PROTECTED] www.ipen.br Quoting Ross Williams [EMAIL PROTECTED]: Hi All, Does anyone know an appropriate source of standard reference materials for a line profile standard, like NIST SRM 660a (LaB6) - other than NIST, as they are out of stock and ...is expected to become available by November 2009. Thanks, Ross
RE: Kapton capillaries
Thank you for your suggestions. Dipo Omotoso From: Brian H. Toby [mailto:[EMAIL PROTECTED] Sent: Friday, November 16, 2007 3:04 PM To: rietveld_l@ill.fr Subject: Re: Kapton capillaries Could someone please suggest a source for purchasing kapton capillaries? A search on the internet drew a blank. Try polyimide rather than kapton. We have used MicroLumen as a vendor: http://www.microlumen.com/ Brian
X-ray scattering contrast Fe/Cu
Dear Rietvelders Does anyone know whether the scattering contrast of Fe and Cu is large enough to refine their occupancies from a single X-ray powder pattern or would multiple wavelength patterns help? Thanks for your advice. Regards Franz Werner -- Pt! Schon vom neuen GMX MultiMessenger gehört? Der kann`s mit allen: http://www.gmx.net/de/go/multimessenger
