Yb/Er doped hexagonal β‐NaLnF4 (Ln = Gd, Y, Lu) are regarded as the most efficient green upconversion (UC) materials. Unfortunately, β‐NaLnF4 is quite difficult to grow as monocrystal owing to cubic‐to‐hexagonal phase transition during cooling. As an alternative, herein a nanocrystallization controllable strategy to synthesize monodisperse whole‐family β‐NaLnF4 (from NaLaF4 to NaLuF4) embedded bulky glass ceramics is reported. A series of structural and spectroscopic characterizations indicate that Na content and Al/Si ratio are the most important factors to determine phase‐selective NaLnF4 crystallization in the aluminosilicate oxyfluoride glasses. Impressively, such nanocomposites are evidenced to be ideal hosts for upconversion luminescence of Yb3+/Er3+ dopants and as the proof‐of‐concept experiments, their applications in a random laser and incoherent LED‐excitable upconverting device as emitting media are demonstrated. It is expected that this study will provide a deep understanding for controllable crystallization in glass and extend the practical applications of glass ceramics in optoelectronic fields.

To reduce the discharge of the standard bulk Micromegas and GEM detector, the GEM-Micromegas detector was developed at the Institute of High Energy Physics. Taking into account the advantages of the two detectors, one GEM foil was set as a preamplifier on the mesh of Micromegas in the structure and the GEM preamplification decreased the working voltage of Micromegas to reduce the effect of the discharge significantly. At the same gain, the spark probability of the GEM-Micromegas detector can be reduced to a factor 0.01 compared to the standard Micromegas detector, and even the higher gain could be obtained. In the paper, the performance of the detector in X-ray beam was studied at 1W2B Laboratory of Beijing Synchrotron Radiation Facility. Finally, the result of the energy resolution under various X-ray energies was given in different working gases. It indicates that the GEM-Micromegas detector has the energy response capability in the energy range from 6 keV to 20 keV and it could work better than the standard bulk-Micromegas.

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