Low-molecular-weight compounds often crystallizes to systems with 100% crystallinity. There are only a few examples where a small amorphous fraction, characterized by a glass transition, remains after long time crystallization from the melt. The crystallization of such a glass-forming low-molecular-weight compound was investigated in order to monitor the change of the molecular dynamics with increasing crystallinity by dielectric spectroscopy and differential scanning calorimetry (DSC). The measurement of the dielectric α-relaxation was performed in real time during isothermal crystallization above the glass transition. At high crystallinities (above 90%) a shift of the peak position and a broadening of the dielectric spectrum was observed. The calorimetric glass transition temperature shifts in the same region for about 15 K to higher temperatures. No direct information about the morphology of the samples is available at the moment but indirect measurements indicate a layerlike crystalline structure. Then the remaining amorphous fraction can be considered between the crystal layers and the observed changes in the relaxation behavior may be caused by spatial confinement in the order of nanometer.
The guidance characteristics of three different translation stages for application as the driver in a high precision displacement transducer calibration instrument (measuring laser) were assessed. A high voltage PZT tube, a low voltage three-segment PZT, and a corrugated diaphragm displacement device with a magnetic coil drive were investigated. The maximum yaw and pitch angles of the PZT tube were 8 and 5′′, respectively, for a translation of 3 μm. The maximum guiding deviation of the three-segment PZT for a displacement of 13 μm was 38′′ (yaw) and 17′′ (pitch) when applying the same voltage to all segments. The maximum guiding deviation, however, was able to be reduced to ±0.4′′ by applying different voltages to individual PZT segments. The guiding deviation of a corrugated diaphragm with a magnetic coil drive was ±0.6′′ (yaw) and ±0.4′′ (pitch) for a displacement of ±100 μm. The corrected three-segment PZT as well as the corrugated diaphragm device are suited for application with the measuring laser of this article.
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