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Languages : en
Pages : 43
Book Description
During this program the following milestones were achieved: (1) Developed a method for synthesizing near pyrochlore-free PMNT starting material for crystal growth using the Columbite process and Pb3O4. Pyrochlore-free starting material prevents the crystals from sticking to the walls of the Pt crucibles and thereby prevents some forms of cracking. An another important development was the use of commercial magnesium niobate that reduced the number of processing steps and time by 50%. (2) Measured the liquidus curve in the PMN-PT phase diagram system for the first time. (3) Grew the first large PNM and PMN 10PT single crystals from nonfluxed melts by the Bridgman method during the first year and had their properties measured. These crystals grew along the 111 direction, their fast growth axis and their properties were consistent with literature values, (4) Grew large, transparent one inch diameter boules of PMN-3PT and PMN-32PT crystals using seed crystals for evaluation of compositional and structural uniformity, crystalline defects, etc. Uniform axial and radial composition was found in one cm diameter boules but axial Ti concentration variations were over 10% in one inch diameter crystals. Samples have been submitted for property measurements and evaluation to NUWC, Tetrad, Washington State University, Penn State University, Hewlett Packard, Wilcoxon, etc. It was found that the properties of the tetragonal PMNT phase (greater than 35% Ti) were not as good as those for rhombohedral crystals.
