X-ray fluorescence is my preferred method to quickly check the composition of a target. This method gives an approximate composition (10%) and can detect all elements heavier than Na in one go -- good to find impurities! The analysis is non-destructive and does not require any sample preparation, provided your target fits into the machine. For a more precise analysis of the stoichiometry, I have used ICP-OES.

Update:

If you or your chemical department hav difficulties to dissolve the target for ICP: Concentrated HCl does the job. The mechanism is reduction of Mn(IV) to Mn(II) by chloride. Careful, it produces chlorine gas.

If the material is solvable in water/acids, ICP is preferable than EDX

Do you want to measure exactly how much of Ca is replacing La? Or if you also want to see if there is any unknown impurity. If the answer is the first one, then you can do a Rietveld refinement and refine the occupancies of La and Ca. But the bottom line is that the data quality (XRD) must be very good for such analysis and one must not be using the Rietveld programs as a 'Black box'.

Dear Sir,

X-ray Photoelectron Spectroscopy (XPS) provides a well-established standard tool

to determine the stoichiometry of the sample. The sample is irradiated with soft

x-rays (in the lab, usually Al-Ka or Mg-Ka radiation is used, with photon energies of 1486.6 eV and 1253.6eV, respectively). The emitted photoelectrons are counted in

dependence on their kinetic energy by use of an energy dispersive analyzer (usually

a kind of spherical capacitor). The kinetic energy of a photoelectron is a direct measure for its binding energy in the atomic orbital from which it was emitted.

The distribution of binding energies is a kind of experimental fingerprint for each element.

By comparing the photoemission intensities (as normalized with the

element and orbital specific cross sections) you can get the relative numbers

of atoms from different elements in terms of at-%.

Please note, that XPS represents a very surface sensitive technique that

probes only a few layers below the actual surface. Therefore, the XPS

results just provide information on the chemical composition of the

surface range of your sample. The latter has not to be representative

for the bulk composition of the sample since in many cases the surface is not equal to a cut of the bulk (relaxation, reconstruction etc.).

In principle, you can probe the elemental composition of the sample

layer-by-layer when performing combined XPS/Ar ion etching experiments

(i.e. elemental depth profiling experiments, see e.g. DOI: 10.1021/la400148h)

As far as I know your institution is equipped with at least one

combined XPS/UPS machine

(see www.iitb.ac.in/stores/tender/201200237_1.pdf).

For further information about this technique (mandatory when to be applied

successfully !!!) please ask the operators of this machine.

Sincerely,

FM

X-ray fluorescence is my preferred method to quickly check the composition of a target. This method gives an approximate composition (10%) and can detect all elements heavier than Na in one go -- good to find impurities! The analysis is non-destructive and does not require any sample preparation, provided your target fits into the machine. For a more precise analysis of the stoichiometry, I have used ICP-OES.

Update:

If you or your chemical department hav difficulties to dissolve the target for ICP: Concentrated HCl does the job. The mechanism is reduction of Mn(IV) to Mn(II) by chloride. Careful, it produces chlorine gas.

Yes, X-ray Fluorescence study will be good. It gives information of the contamination in ppm to some ppb range. Not exactly but roughly, by taking the magnetization measurement you can see the Tc by this you can also have some idea of La/Ca ratio. It is good to have a small pellet with the target of same powder at the time of sample preparation.

Just let me add a comment: While XPS is a very useful tool for surface characterization (I have started using it roughly 20 years ago ...) I think that XPS as well as ICP might not be the method of choice here for the following reasons: I guess that Tarun wants to use his sputter target after the elemental characterization, so any destructive method should be discarded here. Thus ICP and also sputter depth profiling are not adequate. In addition, even if the XPS machine available at Taruns lab allows the transfer of 75 mm diameter sputter target, XPS will only probe the outer surface of the target, and thus, if the material shows some preferrential sputtering, then the XPS analysis might be erroneous as well, at least in terms of the bulk concentrations.

What I would suggest are therefore more bulk-sensitive methods like XRF, as mentioned above. The precision can be as high as with other menthods, it does not need a ultrahigh vacuum environment, and its certainly non-destructive. O.k., if you want to measure the oxygen content as well, then you should perform the analysis in vacuum. But this is not a big effort.

Another feasible technique is GDOES (glow discharge optical emission spectroscopy) - you simply measure what is sputterred from your surface, and if the calibration is done properly, the results are quantitative. But - like sputter depth-profile XPS, it is destructive ...

Best regards to all, Dirk

Rutherford backscattering spectrometry should be a suitable equipment for your purpose.