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Spurenelementverteilung in Siliciumcarbid-Einkristallen - Vergleich analytischer Feststoffmethoden
(2006)
The correlation between composition and structure of unpoled relaxor ferroelectric (1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 (PZN-PT) solid solutions around the morphotropic phase boundary was studied by Rietveld refinement of X-ray powder diffraction patterns of crystals with x=0.060.13 grown by a solution technique. It was found that PZN-PT exists with the rhombohedral structure only below x=0.06. The rhombohedral R3 m phase coexists with the tetragonal P4 mm phase between x=0.08 and 0.11 and above x=0.11 PZN-PT is purely tetragonal. In addition a metastable monoclinic phase (Pm) forms during cooling after crystal growth in the composition range x=0.060.11. The volume fraction of this monoclinic phase is a maximum in the most interesting composition range, i.e. x=0.080.09. The amount of monoclinic phase is enhanced further by mechanical treatment as the pulverization of the crystals for X-ray powder diffraction analysis which induces a tetragonal-to-monoclinic phase transition.