A new type of micro-X-ray diffractometer focused by polycapillary optics

Abstract

Micro-X-ray diffraction (μ-XRD) plays a significant role in measuring the phase structures of small samples or micro areas of larger samples. In this article, we propose a new type of desktop micro-X-ray diffractometer named μ-Hawk focused by polycapillary optics. It consists mainly of a microfocus X-ray tube, polycapillary optics, receiving slits, a silicon drift diode (SDD) X-ray detector integrated with single/multi-channel pulse analyzer, independently rotating <i>θ</i>-<i>θ</i> goniometer, high precision <i>XYZ</i> sample stage, computer programs developed by LabVIEW codes, etc. The main interface of the program has micro-X-ray diffraction analysis mode and micro energy dispersive X-ray fluorescence analysis mode. In addition, the monochromatization of X-ray, the angular resolution and the accuracy of the results of μ-Hawk are discussed. In order to demonstrate the feasibility of the instrument, the phase of micro area in the middle of the first stroke on the Chinese character “Jiao” from a 5-Jiao coin (Chinese currency) is measured by the μ-Hawk, and the phase of a copper wire 140 μm in diameter is also detected by it. After that, the phase of 1.0 mm × 0.6 mm area on the welding joint of the motherboard from an iPhone is two-dimensionally scanned by μ-Hawk. The <i>θ</i>-<i>θ</i> scanning is performed at each detected point inside the two-dimensional area. Four motors drive the <i>X</i> and <i>Y</i> axis of the sample stage as well as the <i>θ</i>₁ and <i>θ</i>₂ axis of the goniometer to accomplish the above functions. The results show that the micro energy dispersive X-ray fluorescence analysis mode of μ-Hawk can provide elementary reference information for the analysis of phase structure. Compared with conventional X-ray diffractometer, the μ-Hawk can detect the same diffraction peaks on the coin with lower background. Furthermore, the accurate diffraction peaks can be measured with a lower power and shorter time. The measured results can better reflect the true phase structure of the micro area. Six diffraction peaks and their phases can be clearly identified from the diffraction pattern of the copper wire. For the welding joint, the phase mapping of SnO₂(3 1 2) is acquired through data processing. Therefore, the μ-Hawk can adapt to the micro-X-ray diffraction analysis of small samples or micro areas of samples as well as the two-dimensional scanning analysis of phase mapping. The μ-Hawk exhibits the unique advantages of accomplishing accurate micro-X-ray diffraction analysis, convenient software, low working power, time saving, and small in size. It indicates a wide application prospect in the fields of materials, geosciences and heritage protection.