Labnotes Powder diffraction


Transmission and Bragg-Brentano measurements showing a significant increase in intensity for the data collected with the MYTHEN 1K silicon strip detector in comparison to the STOE linear PSD.

Measurements of Li2SrSiO4, K3[Fe(CN)6], Fe and Mn2CrO4 applying a scintillation counter and a si pin diode point detector

Although scintillation counters are still widely used there are more sophisticated types of point detectors with higher quantum efficiency and the possibility to directly discriminate the energy of the incident radiation. Therefore samples of Li2SrSiO4, K3[Fe(CN)6], Fe and Mn2CrO4 were investigated using a STOE STADI MP with pure Cu Kα1 radiation.

The data measured with a scintillation counter (with and without a secondary beam monochromator) were compared with data from a Si PIN diode point detector. The latter allows to cutting off the fluorescence of Fe/Mn completely, which results in data outclassing a scintillation counter with secondary beam monochromator in absolute intensity and resolution.

The Si PIN diode point detector is superior to a scintillation counter without secondary beam monochromator in terms of the signal-to-noise ratio as well as the FWHM of the reflections due to the better quantum efficiency and lower height divergence.

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Influence of the Wavelenght for PDF Calculations using a STOE STADI P Diffractometer in Transmission Mode and the DECTRIS Mythen 1K Detector

A STOE STADI P powder diffractometer with Ge(111) monochromator yielding pure Ka1-radiation and the Dectris MYTHEN 1K detector has been chosen for PDF calculation experiments on Naphtalen (C10H8). For Cu K(alpha)1-radiation the Stoe Stadi P has been equipped with a Dectris MYTHEN 1K with 320 μm, for Mo K(alpha)1-radiation with a MYTHEN 1K with 450 μm and for Ag K(aplha)1-radiation with a MYTHEN 1K with 1mm chip size. Synchrotron data has been taken at beamline X17A at NSLS Brookhaven (λ=0.1839Å).

The DECTRIS MYTHEN 1K Strip Detector: Performing Ultra High Resolution Measurements on STOE STADI P and STADI MP Diffractometer

The MYTHEN 1K detector from DECTRIS  has been implemented on STOE’s STADI P and MP diffractometer and used as the ultimate PSD for fast measurements with ultra high resolution. With a NIST SRM660a LaB6 standard powder sample, an angular resolution below 0.03° 2(Theta) FWHM can be achieved.

In the optimized setup, the detector simultaneously collects an angular range of 12.5° 2(Theta) with native data point intervals of 0.01° 2(Theta). In the expert mode, patterns with data point intervals up to 0.005° 2(Theta) can be measured. Due to its wide detector window, the MYTHEN 1K detector collects very fast, additionally keeping the outstanding angular resolution constant over the complete opening.

Qualitative PDF Analysis of Pigment Yellow 213, C23H21O9N5

To observe the influence of the wavelength and the detector noise using a laboratory powder diffractometer for the PDF determination and the maximum evaluable Q-value a 1mm glass capillary has been filled with Pigment Yellow 213 (PY213) and adjusted on a goniometer head of a STOE STADI P powder diffractometer in Debye-Scherrer geometry at the STOE application lab.

Closed cycle He-Cryostat for Stadi P

Low temperature measurement of TbVO4 with a closed cycle helium cryostat and a STADI P.

Fast high temperature measurement

STOE provides the ideal equipment for powder diffractometer systems to observe and evaluate transitions in nonambient environments. With the ultrafast MYTHEN 1K Stripdetector manufactured by DECTRIS very rapid measurements can be perfomed. Highest quality data is obtained with the STOE capillary furnaces for powder investigations at high temperatures. The STOE furnaces can be mounted on every STADI P or MP diffractometer (moving circles or fixed stage).

Small Angle Measurements using the STOE STADI P Standard Setup

Two measurements using the same settings had been accomplished, one with the sample material and the other with an empty sample holder. The latter had been subtracted from the first, to eliminate effects of the primary beam. It is admirable to see that small angle measurements down to 0.2° 2q (using Cu K(alpha)1-radiation) or appr. d-values of 440 Å can be executed with a STOE STADI P without any further equipment like i.e. a Kratky collimator etc.

Using the DECTRIS Mythen 1 K Strip Detector – Fast and High Resolution Measurements on STOE Powder Diffractometers

The DECTRIS MYTHEN 1K strip detector has been implemented to the STOE powder diffractometer and
software. The examples show to some extent the possibilities of this combination of outstanding equipment for powder diffraction experiments. Extreme fast measurements of typical powder samples are now possible due to the high sensitivity of the MYTHEN 1K detector. A full pattern from 0° to 120° 2q can be recorded in 60 seconds with a still good signal to noise ratio as shown in the labnote.

STOE STADI P: Best Data Quality using Transmission-/Debye-Scherrer-Geometry

Though still less common in the crystallographers’ community, the Transmission geometry is the method of  hoice for the investigation of powder samples. Using a Stoe Stadi P powder diffractometer the focusing Ge(111) monochromator yields pure K(alpha)1-radiation for the highest resolution in 2(Theta) (FWHM < 0.03° !). Furthermore the Transmission geometry provides reliable intensities over the full 2(Theta) scale.
Transmission geometry data never suffers from height displacement, samples measured in a capillary are nearly unaffected by the distracting effects of preferred orientation. Even the smallest amount of samples can be evaluated when prepared between two foils. Besides this micro sampling Transmission geometry enables diffraction measurements at the lowest 2q angles.

Ag-Kα1 radiation and the new HR-PSD

Measurement of LaB in a 0.3mm capillary on a STOE STADI P powder diffractometer with Ag-Kα1 radiation in Debye-Scherrer mode up to 90° 2Theta (d=2.75A!).

Reflectometry measurements on a Stadi MP

The properties of thin films affect their reflection and interference characteristics. The two most common ways to measure these are reflectometry and ellipsometry. The STOE thin film attachment uses the total scattering method and detects the reflected amount of X-ray radiation from a thin film. It allows analyzing the thickness of layers in the nanometre scale. For example, single-layer or multilayer films of semiconductor process films can be analyzed.

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