Investigation of the Growth of Lead Magnesium Niobate - and Lead Zinc Niobate - Lead Titanate Solid Solution Single Crystals by the Bridgeman Technique PDF Download
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Author:
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Category :
Languages : en
Pages : 43
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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.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 43
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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.
Author: Edward Peter Gorzkowski
Publisher:
ISBN:
Category : Crystal growth
Languages : en
Pages : 310
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The influence of excess PbO on {001} single crystal growth was studied in the range of 0--10 vol% PbO. It was found that up to 1.5 vol% PbO, the amount of single crystal and grain growth increased with increasing PbO additions. At higher PbO contents, however, the growth becomes independent of liquid fraction for all annealing times. In addition since the matrix grains were faceted and the growth best fit parabolic kinetics, interface reaction control was deemed the most likely growth mechanism.
Author: Adam Matthew Scotch
Publisher:
ISBN:
Category : Crystal growth
Languages : en
Pages : 248
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Relaxor-based ferroelectric single crystals of Pb(Mg1/3Nb 2/3)O3-PbTiO3 [PMN-PT] have been produced via the Seeded Polycrystal Conversion [SPC] technique. Polycrystalline precursors of PMN-PT are converted to single crystals by inducing the boundary of a seed crystal to migrate through a polycrystalline matrix. The quality of PMN-PT single crystals grown by SPC is directly influenced by the microstructure of the polycrystalline precursor. The goal of this work was to examine the factors that controlled the final microstructure of the matrix and grown single crystals and to characterize their effects on properties.
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ISBN:
Category :
Languages : en
Pages : 136
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This final report covers the work carried out under ONR Grant NOOOl4-99-0530 developing the Thermodynamic Phenomenology to describe the properties of Lead zinc niobate: Lead titanate (PZN:PT) and Lead magnesium niobate: Lead titanate (PMN:PT) single crystals, over the period May 1, 1999 to June 30, 2001. Early into these studies it became apparent that the solution grown PZN:PT crystals at compositions close to the morphotropic phase boundary were more homogeneous with lower concentration gradients than the then available Bridgeman grown PMN:PT so the major effort was focused upon the PZN:PT family.
Author: Aneta Slodczyk
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ISBN:
Category :
Languages : en
Pages : 302
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Author: Madhana Sunder
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ISBN:
Category :
Languages : en
Pages : 314
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Author: James Herriott
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Category : Bismuth crystals
Languages : en
Pages : 30
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Author: Samuel Taylor
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Category :
Languages : en
Pages : 0
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Lead magnesium niobate-titanate, Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT), and lead indium niobate-magnesium niobate-titanate, Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) ferroelectric single crystals are widely used in current and next generation medical ultrasound devices for their high signal strength and high frequency capabilities. With technology innovations, single crystal elements in transducers have become small enough that geometry induced domain clamping can severely limit the dielectric properties of the material and must be taken into consideration. Previous work on single crystal PMN-PT and PIN-PMN-PT has demonstrated that a sample with geometries on the scale of the materials ferroelectric domain size will cause domain clamping. [1] Those studies only evaluated single crystals with polished surface finishes. During preparation of a crystal sample, machining stresses can cause permanent lattice distortions, inducing a surface dead layer, an area of distorted lattice near the surface that is no longer ferroelectric. [2] The geometry induced domain clamping study used samples with essentially no surface dead layer. In medical ultrasounds, the low acoustic impedance of human tissues requires impedance matching layers to be adhered to the crystal surface within the transducer in order to transition the sound wave from the high impedance crystal to the low impedance human tissue. Most bonding techniques require a crystal surface rougher than that obtained from a traditional polishing process. A rougher surface will have high stress introduced deeper into the part due to the machining process. This creates a surface dead layer where the lattice is permanently distorted and no longer exhibits ferroelectric behavior. This will reduce the percent volume of ferroelectric material in the part, reducing overall ferroelectric properties/behavior. In this study, commercial surface finish techniques, including ID saw, wire saw, rough surface grinding and fine surface grinding were used to prepare crystal samples of varying thickness to evaluate the thickness and surface roughness dependence of PMN-PT and PIN-PMT- PT single crystals dielectric properties and ferroelectric behavior. All the samples studied met current commercial matching layer adhesion requirements for surface roughness. The ferroelectric crystals were polarized under both DC and AC fields. Electrical properties were measured after DC poling and AC poling. AC poling response was measured to observe the polarization hysteresis behavior of each sample. The primary electrical properties of interest were the thickness mode electromechanical coupling coefficient (kt), strain free component of the relative dielectric permittivity ([epsilon]r) and the coercive field (Ec), as well as the general shape and evolution of the polarization hysteresis loop through multiple measurements. With the ID sawn, wire sawn and rough surface finishes, both PMN-PT and PIN-PMN-PT crystals exhibited thickness dependent domain impingement. PMN-PT samples showed decreased [epsilon]r and non-characteristic PE hysteresis below 350[mu]m thickness. Although PIN-PMN-PT samples showed degradation in the ferroelectric hysteresis loop at thicknesses just below bulk thickness, [epsilon]r was maintained for samples of at least 400[mu]m thickness. For both crystal compositions, the surface dead layer occupied enough volume to result in a measurable detrimental effect on poling and electrical properties. The effects of the surface dead layer on ferroelectric behavior of the crystal samples were similar to the dimensional pinning of domains in thin polished samples of PMN-PT. With similar surface preparation, PIN-PMN-PT crystals also exhibited low properties, unlike in a polished sample. Using a fine grind technique, thin samples of PIN-PMN-PT could be poled and still maintain normal bulk properties and polarization behavior. This research focused on crystals with compositions near the morphotrophic phase boundary (MPB). This study concluded that in commercially processed PIN-PMN-PT and PMN-PT crystal samples, the main contributing factor to domain impingement is the surface dead layer, not the part geometry. As the surface finish is improved, the lattice damage caused by machining stress is reduced, therefore reducing the depth of the surface dead layer into the sample and reducing the overall volume percent of the sample that cannot be poled. As surface machining techniques are refined, creating a smoother surface, geometry induced domain impingement starts to play a larger role in ferroelectric behavior.
Author: Aneta Słodczyk
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ISBN:
Category :
Languages : en
Pages :
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Author: Alp Sehirlioglu
Publisher:
ISBN:
Category :
Languages : en
Pages : 420
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