 Hello everyone, welcome to this material characterization course. In the last class, we just looked at the applications of X-ray diffraction and we looked at typically three cases. One is crystal structure determination and we also looked at how to look at the stress measurements that is a basic principles of stress measurements and also we looked at the phase identification in a phase mixture. We looked at all those very fundamental ideas behind application of this X-ray diffraction and it is how the intensity is calculated and so on. And today's class, I will just show you some demonstrations through the laboratory videos. I will take you to our XRD lab and then show the equipment details, how the X-ray diffraction equipment look like and what are the primary components and how one would perform an X-ray diffraction experiments in a polycrystalline material. So you will get a basic idea from this though you will not be able to do other detailed experiments since it is only a part of this material characterization course, I thought it would be a very nice idea if you have some detail about how the equipment will look like and what are the basic details about in XRD machines. So if you look at the screen where I started showing this is the Brooker X-ray diffractometer and you can see that it is all enclosed in a big box, you can see it in a long shot and you can also see our one of the scholars in our department is going to operate this machine for us and I will just show you the details one by one. So this is X-ray diffractometer and you have the power console here and on and off and everything so it is a long shot and what you are going to look at again from okay now we have opened this equipment now you are seeing the details of the diffractometer what you are seeing in the background I mean backside the big circular disk is a gonometer it is called a gonometer or and it is also referred as a diffractometer circle and then what you are now seeing is everything in a close-up shot and do not worry you will be seeing this for very long time so you get the details. Now this is the specimen stage where your specimens are kept whether it is a bulk sample or a powder sample a bulk sample is directly kept on this whereas the powder sample is mixed with some medium and it is kept on a glass slider something like that and this is a specimen stage we will talk about it much more detail. So what we need to know from this equipment is the basic components some of the basic components which you require is the x-ray source this is the x-ray source and from where we will talk about some slits and through which the x-ray beam comes out and then it is made fall on this specimen here so and this is a detector this is a detector again which has got lot of slits inside we will discuss about the role of slits and then you have an x-ray detector in this case. So the primary component is x-ray source a sample stage and a detector you can see that all these three are shown in this and one important thing you have to understand is the x-ray source and a detector is kept intentionally on the gonometer circle you just see that the x-ray source and the detector are going to be on the gonometer circle or you can say that diffractometer circle you just observe these details for some clarity these are all on x, y movement for the specimen stage we will discuss about the importance of this movement okay. The specimen also can go in that semicircle fashion in this manner so what I would like to do is before our scholar perform the experiments let me also explain some of the basic components like you can see that what I would like to explain here is you just I will just stop this video here this is the gonometer circle your x-ray source as well as the detector are kept in the diffractometer circle or gonometer circle and the specimen is always kept in the center here the center stage we will now just discuss the basic requirement of keeping the sample in the center of this gonometer circle and there is a we will talk about x-ray optics before we do that experiment so what I will do is let me draw a line diagram on the blackboard in order to appreciate what you are now seeing so I will draw a focusing geometry so what I have drawn is a focusing geometry for x-ray optics suppose if you have the source here and then it goes to the sample and get reflected here and this is a x-ray source which is falling on the sample in the point B and get focused here in F and you see that the angle between this is 2 theta and this is alpha and this is alpha and you can have the relation here with the circle inscribing the angle and what you have to keep in mind whenever you have the x-ray source which goes into the sample and get back to the point F that is the this is incident ray and this is diffracted ray are getting focused again at a point F so you can say that this is a source of x-ray and this is your detector and this is your sample for example so if you this geometry is maintained for all the scanning for all the scanning for variable 2 theta this is completely maintained for all the wherever you keep variable 2 theta this geometry is maintained and we can write so this is also called a Brantano diffractometer where this kind of geometry is used and then I will draw one more schematic which will show the the para focusing of the gonometer as well as the what the sample you are going to scan during various angles of 2 theta so I will draw two more figure then I will get into the discussion so what I have drawn here is two types of 2 theta angle how this Bragg Brantano geometry or I would say Bragg Brantano para focusing method which is being adopted in this particular diffractometer so you have this is a diffractometer circle or gonometer circle which I showed you in the video and this is your sample which I said that so these two there are we are talking about two circles here one is diffractometer circle or gonometer circle the other is a focusing circle so what is this focusing circle depending upon the 2 theta it is going to vary so you see that you see your as I said that your specimen detector and the source should be in a circle so assume that this is a focusing circle and this is your diffractometer circle depending upon the 2 theta it is going to vary at this way or this way so in this case you see that this is the specimen and the specimen normal and this is the incoming source and this is a diffracted beam which is focused and then you see that the specimen is kept in the circle on the perimeter of the circle of focusing so depending upon the 2 theta you can see that the 2 theta is becoming smaller then you see that the focusing circle is also becoming smaller as the theta 2 theta become bigger then you see that it is the you are focusing circle also so this geometry is preserved and that geometry is called Bragg-Brentano geometry and this kind of a focusing is called para focusing and which is being adapted in this particular diffractometer so with this background now you go back and look at the video you will be able to appreciate what I am trying to say now if you look at the video again what I will do is now you can see the goniometer circle and then let me finish that before I go goniometer circle and this is the source and this is a detector and this is a sample which is kept in the center of the goniometer circle in order to maintain this focusing circle which will be here depending upon it is going to vary right now it is small because now the 2 theta 2 theta is here this 2 theta 2 theta is this is a sample you draw a straight line and this is a diffracted beam so this angle is 2 theta so that is going to vary then you see that the focusing circle is also vary so now we will look at much more detail about this about this is about the basic components of the diffractometer we will now show some of the important components here okay this is what we are now seeing here in the screen is the x-ray tube what is the typical x-ray tube one would look at okay so now you have the better view this is an x-ray tube where in you have the target material which is inside and later we will also open this and then show you some of the details of the x-ray tube that this is how the x-ray tube will look like at least you have some idea and which will go into that source what we have just shown so of course this the whole tube is under the cooling system and then you have the beryllium windows through which the x-ray comes out beryllium windows are transparent to x-rays to that detail I would like to finish so have a close look at this x-ray tube so now we will move on to an experiment now before even go to the experiment let me stop here and then explain little more details about this so I said that the x-ray source is here and it is going to come out through this exit window and you remember the x-rays which are coming out of this window is completely divergent beam and it is divergent beam in all directions so it need to be controlled the one of the way to control this divergence is by through slits and we have a typical slits which are popular and then which are kept inside this and then it is being made to fall or collimated beam is made fall on to this specimen and similarly the detector also will have a lot of slits and filters please remember we are interested in taking only a particular x-ray beam for example k alpha and you will in generally if you without the slits you will also come across k beta and so on so the other radiations are blocked by this filters for example k beta is suppressed you cannot eliminate completely but it can be substantially suppressed as compared to k alpha radiation the filters are here and this is a detector it could be a semiconductor device as well so now I think that is the basic idea you should have about this x-ray diffractometer and then now we can even look at how experiment is being performed in this machine and please remember this stages is a rotating stage it can rotate 360 degrees and also it can move on a semi-circle in the stage which I have mentioned now you can see that a typical stage movement in order to save time I am just cutting some of the shots so that you will be able to see this you can see that the source and detector are moving but still that focusing circle is maintained here to in order to mention that I mean preserve that Bragg-Brentano geometry para focusing geometry you can see that the stage is moving it is measuring the beam with various angles 2 theta angles now we will see that the stage will also move in a semi-circle fashion in order to the one of the primary requirement or the use of this the stage movement is you will be exposing the sample in all possible diffracting planes for example if you are interested in particular plane or if it is a powder sample the statistical important statistically important data you will be able to generate if you are able to rotate this stage in all the three directions like this see that the sample sample is coming towards the front and x and y movement and you will you will be able to appreciate that now we will see that the sample will move in this direction it will rotate in this direction that also you can see yeah what you are now seeing is a top view the sample is now completely rotated you can see in that in that semi-circle stage it has moved now it is coming back you can see that and these rotations are completely exploited in the in the case of a texture measurements which we are not showing we are trying to just show the instrumentation detail and what are the possible you know tilt angles and so on and we will simply look at the basic diffraction data which comes out of this sample the sample which is being used as I think alpha silicon oxide powder and you will see that kind of diffraction data which will be obtained from this experiment you can see that the specimen rotation completely it is a 360 degree okay this is just for your information the x-ray tube which we showed earlier now it has opened up this is your anode material it could be you can change this target material based upon the specimen you are analyzing it could be a chromium or you know chromium target copper target and so on depending upon the type of sample you analyze and what the other dismantled part is okay this is a close up view of this anode just for your information and this is the that beryllium window which we talk about through which the x-rays will come out this is a dismantled part not just an important here but just to for an information how the x-ray tube parts are shown so we will now quickly do a one full set of complete experiment and then generate an x-ray diffraction pattern and then we will see what we get so the data collected from the instrument is completely analyzed by the interface software and we will show you how what kind of data you get and then how it is how the background everything is filtered by the software and then you can have a look at it so let the fresh experiment starts with all the possible 2 theta angles we will not hold this video for the complete experiment we will quickly go to that final results so you see that the sample is kept here and then it is being measured at various 2 theta angles I will skip that step because you have no you know you know that how this diffractometer functions I will quickly forward this video in order to save some time okay now you are seeing that how you are dynamically getting that signal we are viewing through a software you see that typical x-ray diffraction peaks are coming on the screen so all this 2 theta corresponding peak belong to a characteristic peaks of silicon alpha silicon oxide which I just said powder a polycrystalline diffraction pattern typical polycrystalline diffraction pattern will appear like this and you can compare this 2 theta value and go to a JCPDS database to identify particular crystal system of course you have a large number of software parameters to derive the data from I mean information from this basic data and this is a typical x-ray diffraction spectrum you will get I will finish this I will go to the another important aspect of the system whatever we are now seen as a powder diffractometer you see that another important source I would like to show is this the equipment which I am going to show you is another very important x-ray machine which measures the residual stresses in an or a stress measurement system which is industrially important the you can see that this is the equipment typical equipment you have a look at it and then we will discuss about the the function functionality of this equipment so this is an extended arm where you have this I will probably I will stop here and unlike the Bragg-Brentano geometry what we have just witnessed before which is not maintained here and here this is an x-ray source x-ray source are here it is not a diverged beam here it is a parallel beam parallel beam and the x-ray source straight away comes there and then you see that there is a typical connecting rod which is being measured which is clamped through a stand here and the x-ray beams are simply falling on this connecting rod and then you have the two detectors besides this in fact they you are looking at the side view so the detector will move on this the curved of of circle stage like this so the x-rays will come straight on the sample and then get diffracted into the two I mean detectors which is kept side by side to this source so the difference between the previous diffractometer and this is here the x-rays are a parallel beam and and you have the direct collection of the diffracted beam and then you try to analyze the x-ray data so now you can have a close look at this arrangement this is one of the unique facility of this our laboratory stress measurements using x-ray diffraction okay you have now better clarity here yes the source which I am talking about is this x-ray source and the two detectors are kept side by side the one advantage with the this kind of setup is you do not have any restriction on the specimen size any specimen which can be fixed into the stage can be brought you can see that now how the scanning is done the x-ray source can rotate and that off circle and then you can see that this is a source now very clearly source and the detectors are side by side the source in the center and two detectors yeah now it scans for all the two theta measurements here so this is a advantage of this particular mission of any component a big component can be scanned and then you will get the data so with that what I think is you have some basic idea if not very detailed idea how the x-ray diffractometer look like and then how the source and the specimens are kept and how the detectors are kept and what is the basic data you get out of this equipment and we also demonstrated to you the stress measurement equipment how it scans there is a big difference between these two equipments and most importantly the x-ray optics behind these two equipments are also quite different and I hope these equipments and this small demonstrations gave you some basic insight about x-ray diffraction laboratory if you are not able to access this laboratory at least you know now how these equipment look like and how what are the basic operations behind this we have not done elaborate experiment here due to the constraint of the time but I hope you had some basic idea and now you can connect what the what we do I mean theoretically what we study in the books and then what practically you can do it in the laboratory when you have an opportunity to look at these equipments in some other labs now you will have some idea how it is done and how the basic data is generated so that was my intention of doing this laboratory demonstration thank you.