X-Ray Diffractometer; Stadi MP, Stoe

The STOE multipurpose diffractometer enables the determination of both crystal structure and chemical composition of inorganic and organic polycrystalline phases in a polycrystalline material. It is a stationary device with an overall weight of ~ 670 kg and dimensions of 180 x 88 x 205 cm (LxWxH). A Seifert Iso-Debyeflex 3003 high-voltage generator (up to 60 keV) and a STOE linear wire Position Sensitive Detector (PSD) belong to the major equipment. The STOE STADI MP diffractometer operates normally in Bragg-Brentano geometry and is equipped with a curved germanium (111) monochromator, providing CuKa1 radiation (λ = 1.54056 Å) at 40 kV and 30 mA (corresponding to 1.2 kW). Other important characteristics of the diffractometer are the following: 

1. Goniometer consists of two circles with an angular accuracy higher than 0.001o (i.e. step size).
2. 2θ range: -10o to 140o or better depending on selected geometry.
3. PSD can either rotate (step mode: 1.5o-6o) or remain stationary.
4. Scanning feature width lies between 0.1o and 6o, while the recommended scanning step size is 0.01o.

In the case of p-XRD, we are dealing with an invasive method, as a sample with a weight of ~ 100 mg is needed to perform such an analysis, while the entire volume of the investigated sample is going to be probed. The usual set up time amounts to ~ 30 min including calibration of the linear PSD with a standard Si sample with Si(111)-peak at 2θ = 28.443^o (with CuK_a1), while the average measuring time varies a lot. For instance, for p-XRD analysis of a marble sample with 2θ range between 10^o and 70^o, featuring width of 0.105^o, PSD step mode of 1.5^o, time/PSD step of 90 sec and scanning step size of 0.01^o, 60 min are required. After obtaining the results, the processing time of the data depends on the complexity of the analysed sample. Some other device-related limitations and requirements are listed below:

• General description: multipurpose diffractometer 
• Application aim: determination of the crystal structure and composition of different phases
• Mobility: stationary
• Equipment specifications:
  • Seifert Iso-Debyeflex 3003 high-voltage generator (up to 60 keV)
  • STOE linear wire Position Sensitive Detector (PSD)
  • Curved germanium (111) monochromator
  • Cu anode producing CuK_a1 radiation with λ = 1.54056 Å at 40 kV and 30 mA (corresponding to 1.2 kW)
  • High resolution Bragg-Brentano setup as the operating geometry
  • Goniometer consisting of two circles with an angular accuracy higher than 0.001^o (i.e. step size)
  • 2θ range: -10^o to 140^o or better depending on selected geometry
  • Radius of measuring circle: 140-573 mm depending on selected geometry and detector
  • Radius of focusing circle: 80-160 mm depending on selected geometry
  • PSD either moving (step mode: 1.5^o-6^o) or stationary
  • Scanning feature width between 0.1^o and 6^o
• Application requirements: X-ray restrictions and water supply close to the device with a fixed temperature of 15-20 ^oC; 15-25 ^oC and 20-65% humidity
• Sample required: yes, ~ 100 mg powder of the desired material
• Contact required: destructive to artefacts as we need to scratch the material, interaction spot dimensions: the entire volume of the sample is probed
• Limitations: applicable only to crystalline and not to amorphous phases
• Set up time: 30 min including calibration of the linear PSD with a standard Si sample with Si(111)-peak at 2θ = 28.443^o (with CuK_a1)
• Average time for measuring: variable, e.g. 60 min for powder XRD analysis of a marble sample with 2θ range between 10^o and 70^o, featuring width of 0.105^o , PSD step mode of 1.5^o, time/PSD step of 90 sec and scanning step size of 0.01^o
• Software package: STOE powder diffraction WinXPOW, Crystallographica Search Match 3.1 with a database based on the International Centre for Diffraction Data (ICDD), output file as .csm or .pdf (data size ~ 500 KB).
• Output: .raw with a data size of ~ 30 KB
• Contact: Stelios Aspiotis, stylianos.aspiotis"AT"uni-hamburg.de
• Location of the equipment: Mineralogisch-Petrographisches Institut, MPI, (Grindelallee 48, Hamburg)