Vibrational and structural properties of lead-free piezoelectric (1-x)Na0.5Bi0.5TiO3–xCaTiO3 (0 < x < 1.00) solid solutions have been investigated using Raman spectroscopy and X-ray diffraction. Different anomalies were detected and analyzed taking into consideration the phase transition from rhombohedral to orthorhombic phase at room temperature. All Raman bands were interpreted through the variation in the peak positions (frequency) and the corresponding half-widths at half maximum (HWHM) as a function of x. XRD used as a complementary technique to Raman spectroscopy, showed that the rhombohedral – orthorhombic phase transition went gradually through an intermediate phase consisting of a mixture of rhombohedral (R3c) and orthorhombic (Pnma) structures and that the fraction of orthorhombic phase increased with CT composition. The results show that the morphotropic phase boundary (MPB) is located between 0.09 and 0.15.
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Hoe kunnen leeromgevingen in het beroepsonderwijs een rol vervullen bij het oplossen van complexe maatschappelijke problemen? Ilya Zitter, bijzonder lector Leeromgevingen in het Beroepsonderwijs bij Hogeschool Utrecht (HU), onderzoekt hoe je leeromgevingen zo kunt ontwerpen dat een innovatief, lerend systeem ontstaat, zonder sterke scheiding tussen onderwijs en praktijk. Op 25 maart gaf Zitter haar openbare les.
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We need mental and physical reference points. We need physical reference points such as signposts to show us which way to go, for example to the airport or the hospital, and we need reference points to show us where we are. Why? If you don’t know where you are, it’s quite a difficult job to find your way, thus landmarks and “lieux de memoire” play an important role in our lives.
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