1. Sample preparation - Stationary Sample Holders
This presentation gives a description of the preparation of powder samples in PW1172/01 sample holders according to the backloading technique.
The preparation of samples for analysis is of critical importance if accurate and fast results are to be obtained, and the procedures detailed in this section should be careful followed.
Additionally, the introduction of errors, such as contamination, material loss, alteration of composition, especially of the sample surface, and change of lattice type, during the course of sample preparation, and afterwards, should be avoided.
Contamination of the sample can be caused by dust, material from a previous sample which remained in the sample preparation equipment, or by material from the sample preparation equipment resulting from abrasion.
Material loss is attributed to non-quantitative transfer in concentration determining operations (dilution, binder addition), loss of a small fraction of particle size as dust, and material remaining in the sample preparation equipment.
Alteration of composition is attributed to losses of material particles which are of different composition to the average composition. For example, magnetic particles, fine dust, and volatile substances. Also, physical or chemical alteration; that is, by decomposition during preparation, such as oxidation, loss of combined water or carbon dioxide by overheating and pick-up of water or carbon dioxide from the air, or by the addition of materials of different composition such as by contamination.
Change of lattice type; that is, transition to another phase, is attributed to pressure, temperature, or a combination of the two.
The sample surface is only measured up to a depth of 1 or 2 mm in some cases, but in most cases only a hundred microns or even less. Typical examples of errors which can occur here are non-representativeness (sample surface has different composition than the average composition) caused by segregation, adhering particles or extracted particles, smearing and bad particle statistics, non-uniformity (sample surface is not equal for all samples) such as non-flat samples (concave or convex), or differences in surface roughness.
Most of the errors can be avoided if samples are prepared carefully with cleaned equipment in a clean room. Once samples have been prepared they must be stored in a dust-free environment such as desiccators sometimes under vacuum or filled with moisture absorbers like Silica gel. If samples are difficult to handle, use pincers or gloves.
Samples for X-ray analysis should be, in effect, infinitely thick, depending on the energy of the X-ray line and the matrix of the samples. Usually a 2 to 3 mm thickness seems to be sufficient. Once the sample has been prepared, care should be taken that it fits into the holder properly.
To achieve a sufficient sample strength during sample preparation, the sample must be ground very fine, achieving an average grain size of 5 mm, with a maximum grain size of 25 mm. If both hard and soft materials are present together, the required size reduction of particles might be achieved by pressing the sample instead of grinding. This may prevent the softer material being ground by the harder one.

2. Manually Prepared Powder Samples
General powders
PW1811/16
16 mm Æ Powder Samples
PW1811/27
27 mm Æ Powder Samples
PW 1811/00
Aluminum Back Plate
PW1811
The PW1811 sample holders consist of a bottom plate (PW1811/00) and a sample holder ring (PW1811/16 or PW1811/27). These sample holders are intended for the manual or semi-automatic preparation of powder samples, which can be either front-loaded or back-loaded.
The bottom plate supports the powder and enables the automatic loading. The cavity has a diameter of 16 or 27 mm and a height of 2.4 mm.
Application
PW1811 sample holders are used for general powder analysis. Powders, with a particle size less than 25 mm and a small or average density, can usually be analyzed without a binder.

3. Non-standard sample sizes and shapes (1)
Solid samples
PW1812/00
Odd Shapes fixed with wax
or plasticine
PW1812/00
The PW1812/00 is a general-purpose sample holder for solid samples or powders on a solid support.
It consists of a steel loading plate, on which solid samples can be mounted. The samples can be fixed with the use of modeling wax or plasticine.
The diameter of the cavity is 44 mm, the maximum sample height is 6.5 mm.
Application
Analysis of solid samples: irregularly shaped solid materials, metal parts, ceramics, slabs of rock, pressed pellets, or a mounting plate (for example PW1817/32) with a powder specimen.
The PW1812/00 can also hold powder samples pressed into a collapsible aluminum cup (PW1526/50).

4. Non-standard sample sizes and shapes (2)
Coin fixed into sample holder with a small amount of plasticine
Mounting of non-standard samples
Samples irregular in size and shape can be mounted in the sample holder with a little bit of wax or plasticine. The top surface of the outer rim of the sample holder is the reference plane for accurate sample height alignment. Correct sample height alignment is of utmost importance in focusing diffraction geometries, like the Bragg-Brentano geometry.

5. Automatically Prepared Powder Samples
Pressed samples
PW1812/35
Steel Press Ring (cement etc.)
PW1812/35
The PW1812/35 is a sample pressing ring which can be used with (semi-) automatic sample preparation equipment with a piston diameter of 35 mm.
The powder is spread directly into the ring.
The top and bottom profiles and the external shape of the ring are compatible with automatic / robotic sample handling equipment, e.g. the PW3065 sample changer used in X’Pert PRO.
Application
Automatic analysis of pressed powders, e.g. in the cement industry or process control applications. The fit in Philips Analytical X-ray spectrometers as well.

6. Circularly Shaped Solid Samples (1)
Sample holder for Membrane filters, Metal plates, Pressed pellets
PW1813/26, 26 mm Æ Steel Ring
PW1813/32, 32 mm Æ Steel Ring
PW1813
PW1813 sample holders are designed to mount thin circular solid samples, such as pressed pellets, metal plates, membrane filters or powder sample mounting plates.
The PW1813 sample holder consists of a sample holder ring and a bottom plate with a spring to mount flat, circular samples. An aluminum support plate is provided to mount membrane filters.
The PW1813 sample holder ring is available in three inner ring diameters sizes:
PW1813/26: For samples with a diameter within the range of mm.
PW1813/32: For samples with a diameter within the range of mm.
PW1813/40: For samples with a diameter within the range of mm.
The maximum sample thickness is 6.0 mm.
Applications
Analysis of air filters for occupational / environmental dust with filter sizes 25 mm (1 inch), 32 mm (1¼ inch) and 38 mm (1½ inch). Pressed pellets, metal plates and other solid objects which fit in the dimensions as given above.
The minimum 2Theta angle for each type is dependent on the divergence slit and mask dimensions.
PW1813/32, 40 mm Æ Steel Ring

7. Circularly Shaped Solid Samples (2)
Spring-loaded sample mounting
Spring-loaded mounting of circular solid samples
A thin circular solid sample is inserted into the sample holder ring. A spring is used to secure the sample at the correct height for accurate X-ray analysis.

8. Powder sample pressed in
PW1526/50 Aluminum cup
Pressed Samples
Pressed samples
The PW1813/40 can also be used to hold powder samples pressed into a collapsible aluminum cup (PW1526/50).
A uniform amount of material, under constant pressure, for a set period of time, will ensure a sample of constant and uniform density. Using a powder press will also ensure that the height of the sample is reproducible, thus avoiding shifts in 2 angle.
Ideally, mechanical pelletizing should be carried out using a powder sample press with an adjustable pelletizing pressure, which can be applied for a pre-determined time. If small numbers of samples are going to be analyzed, a hand operated powder sample press can be used (for example, a Philips PW4020 Mini Press). For even more uniformity and / or larger numbers of samples, an automated sample press can be used (for example, a Herzog HTP40).
The sample surface should be flat and flush with the sample holder. Therefore, back-loading against a flat plate is recommended.
The sample, pressed into an aluminum cup, fits into the PW1813/40 sample holder.

9. Glass Capillary or Fiber Sample
Glass capillary mounted with plasticine on a Si support plate
Fiber samples or glass capillaries
When only a small amount of material is available, or when the samples under investigation are sensitive to oxygen or humidity, or are dangerous to the operator’s health, glass capillaries are used for sample preparation.
Glass capillaries can be attached to a zero-background holder PW1817/32 with a minute amount of grease or modeling wax at the tips. The PW1817/32 is a disc made from a silicon single crystal, with dimensions of 32 mm diameter and 2 mm height. It is obliquely cut to yield an extremely low background. It fits in the PW1813/32 sample holder.
Short fibers can be attached in the same way as glass capillaries on the silicon support plate. Long fibers can be wound around the plate.
Please note: The silicon wafers must be cleaned carefully before use, preferably using an ultrasonic bath.

10. Small Amounts of Powder
Small amount of powder sprinkled onto a PW1817/32 Si support plate
PW1817/32 for small amount of powder and low background measurements.
Small amounts of powder
The PW1817/32 can also be used as a support plate for extremely small amounts of powder (even less than 1 mg). The powder can be sprinkled directly onto the silicon wafer. To obtain the lowest background, apply a drop of water or a smear of vaseline (petroleum jelly) to the wafer, and then sprinkle the powder sample onto it.
Sprinkling minimizes the occurrence of preferred orientation.

11. Clay Minerals and Paste-like Materials
Sample holder with support plate and spring
PW1814/32 32 mm Æ
Sample Holder for
PW1817/32 and PW1816/32
PW1814/32
The PW1814/32 sample holder consists of a sample holder ring and a bottom plate with a spring and an aluminum support plate. It can be used for the analysis of all types of paste-like materials, spread onto the aluminum support plate. The maximum diameter of the paste layer is 29 mm. The thickness must be between 0.4 and 0.5 mm.
Alternatively, it can be used in combination with PW1816/32 ceramic filter plate for the analysis of clay minerals. The zero-background holder PW1817/32 can be used as a support plate for transparent samples.
Applications
Grease, margarine and other paste-like materials can be spread onto the support plate with a spatula or a knife.
Clay minerals can be applied using the suction method, taking into account the dimensions of the clay layer.
The PW1817/32 Silicon Single Crystal may be used as an alternative for the support plate to offer a low background.

12. PW1816/32 Ceramic plate for clay slurry
Clay Minerals
PW1816/32 Ceramic plate for clay slurry
Clay minerals
Clay specimen are sometimes prepared with the so-called suction method. This method is applied to remove the water from the slurry. The clay layers are applied onto a PW1816/32 ceramic filter plate. The filter plate is made of porous alumina (aluminum oxide) with a mean pore size of 3.5 m. The diameter range of the disc is between 31.8 mm and 32.2 mm, with thicknesses between 3.3 mm and 3.7 mm.
The PW1816/32 ceramic filter plate fits into the PW1814/32 sample holder ring.

13. PW1817/32 Si support plate used as zero-background holder
Paste-like Materials
PW1817/32 Si support plate used as zero-background holder
Paste-like materials
Paste-like materials, such as grease and margarine can be spread onto the aluminum support plate (part of PW1814/32) with a spatula or a knife. The PW1817/32 zero-background holder is used for transparent materials to yield a low background intensity.