Optical Properties of Lead Magnesium Niobate-lead Titanate (PMN-PT) and Strontium Barium Niobate (SBN) Thin Films PDF Download
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Author: Ka-yi Chan
Publisher:
ISBN:
Category : Pulsed laser deposition
Languages : en
Pages : 252
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Author: Ka-yi Chan
Publisher:
ISBN:
Category : Pulsed laser deposition
Languages : en
Pages : 252
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Author: Michael Christopher Wagner
Publisher:
ISBN:
Category :
Languages : en
Pages : 41
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As the range of applications for electro-optic materials continues to grow, so does the need to identify and characterize new materials with improved electro-optic responses. A promising electro-optic material which has yet to be widely utilized is Lead Magnesium Niobate-Lead Titanate (PMN-PT) ceramic. In an effort to better characterize and understand the material, this work employed FTIR spectroscopy to calculate the refractive index of PMN-PT over a wide range of optical frequencies. Through analysis of interference fringes, the dispersion curve is calculated between 10,500 cm1 and 1200 cm1 (approximately 955 nm and 8.3 Îơm) containing nearly two thousand data points with an assumed accuracy of three decimal places. Additionally, capacitance bridge analysis is used to characterize the effect of temperature on the dielectric constant of PMN-PT. Special attention is given to the relationship of refractive index and dielectric constant so that a temperature study of the dielectric constant can be used to infer additional physical characteristics of PMN-PT.
Author: Samuel Taylor
Publisher:
ISBN:
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:
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ISBN:
Category : Ceramics
Languages : en
Pages : 254
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Author:
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ISBN:
Category : Engineering
Languages : en
Pages : 2264
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Since its creation in 1884, Engineering Index has covered virtually every major engineering innovation from around the world. It serves as the historical record of virtually every major engineering innovation of the 20th century. Recent content is a vital resource for current awareness, new production information, technological forecasting and competitive intelligence. The world?s most comprehensive interdisciplinary engineering database, Engineering Index contains over 10.7 million records. Each year, over 500,000 new abstracts are added from over 5,000 scholarly journals, trade magazines, and conference proceedings. Coverage spans over 175 engineering disciplines from over 80 countries. Updated weekly.
Author: Michael James Nystrom
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Madhana Sunder
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ISBN:
Category :
Languages : en
Pages : 314
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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.
Author:
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ISBN:
Category : Chemistry
Languages : en
Pages : 2726
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Author: Stephen R. Gilbert
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ISBN:
Category :
Languages : en
Pages :
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