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Crystals, Volume 4, Issue 3 (September 2014), Pages 190-426

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Research

Jump to: Review

Open AccessArticle Combinatorial Frequency Generation in Quasi-Periodic Stacks of Nonlinear Dielectric Layers
Crystals 2014, 4(3), 209-227; doi:10.3390/cryst4030209
Received: 10 May 2014 / Revised: 6 June 2014 / Accepted: 9 June 2014 / Published: 1 July 2014
Cited by 1 | PDF Full-text (686 KB) | HTML Full-text | XML Full-text
Abstract
Three-wave mixing in quasi-periodic structures (QPSs) composed of nonlinear anisotropic dielectric layers, stacked in Fibonacci and Thue-Morse sequences, has been explored at illumination by a pair of pump waves with dissimilar frequencies and incidence angles. A new formulation of the nonlinear scattering [...] Read more.
Three-wave mixing in quasi-periodic structures (QPSs) composed of nonlinear anisotropic dielectric layers, stacked in Fibonacci and Thue-Morse sequences, has been explored at illumination by a pair of pump waves with dissimilar frequencies and incidence angles. A new formulation of the nonlinear scattering problem has enabled the QPS analysis as a perturbed periodic structure with defects. The obtained solutions have revealed the effects of stack composition and constituent layer parameters, including losses, on the properties of combinatorial frequency generation (CFG). The CFG features illustrated by the simulation results are discussed. It is demonstrated that quasi-periodic stacks can achieve a higher efficiency of CFG than regular periodic multilayers. Full article
(This article belongs to the Special Issue Photonic Crystals)
Open AccessArticle Quasi-Linear Polarized Modes in Y-Rotated Piezoelectric GaPO4 Plates
Crystals 2014, 4(3), 228-240; doi:10.3390/cryst4030228
Received: 30 April 2014 / Revised: 14 June 2014 / Accepted: 16 June 2014 / Published: 7 July 2014
Cited by 1 | PDF Full-text (2237 KB) | HTML Full-text | XML Full-text
Abstract
The propagation of both surface and flexural acoustic plate modes along y-rotated x-propagation GaPO4 piezoelectric substrates was studied for several y-cut angles: the phase velocity and coupling coefficient dispersion curves were theoretically calculated for two different electroacoustic coupling [...] Read more.
The propagation of both surface and flexural acoustic plate modes along y-rotated x-propagation GaPO4 piezoelectric substrates was studied for several y-cut angles: the phase velocity and coupling coefficient dispersion curves were theoretically calculated for two different electroacoustic coupling configurations. The investigation of the acoustic field profile across the plate thickness revealed the presence of thin plate modes having polarization predominantly oriented along the propagation direction, and hence suitable for operation in liquid environment. These modes include the linearly polarized Anisimkin Jr. and the quasi longitudinal plate modes, AMs and QLs, showing a phase velocity close to that of the longitudinal bulk acoustic wave propagating in the same direction. The temperature coefficient of delay (TCD) of these longitudinal modes was investigated in the −20 to 420 °C temperature range, in order to identify thermally stable or low TCD cuts. The power flow angle, i.e., the angle between the phase and group velocity vectors, was also estimated to evaluate the substrate anisotropy effect on the acoustic wave propagation. The GaPO4 intrinsic properties, such as its resistance to high temperature and its chemical inertness, make it especially attractive for the development of acoustic waves-based sensors for applications in harsh liquid environment. Full article
(This article belongs to the Special Issue Piezoelectric Crystals)
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Open AccessArticle Temperature-Dependent Phase Transition in Orthorhombic [011]c Pb(Mg1/3Nb2/3) O3-0.35PbTiO3 Single Crystal
Crystals 2014, 4(3), 262-272; doi:10.3390/cryst4030262
Received: 29 April 2014 / Revised: 9 June 2014 / Accepted: 25 June 2014 / Published: 11 July 2014
Cited by 3 | PDF Full-text (915 KB) | HTML Full-text | XML Full-text
Abstract
Relaxor [011]c PMN-0.35PT single crystal phase transition characteristics are investigated through various methods including variable temperature dielectric properties, X-ray diffraction, bipolar ferroelectric hysteresis loops (P-E) and electric-field-induced strain (S-E) hysteresis loops measurements. The results reveal that two phase transitions exist within [...] Read more.
Relaxor [011]c PMN-0.35PT single crystal phase transition characteristics are investigated through various methods including variable temperature dielectric properties, X-ray diffraction, bipolar ferroelectric hysteresis loops (P-E) and electric-field-induced strain (S-E) hysteresis loops measurements. The results reveal that two phase transitions exist within the range from room temperature to 250 °C: orthorhombic (O)-tetragonal (T)-cubic (C). The O-to-T and T-to-C phase transition temperatures have been identified as 84 °C and 152 °C, respectively. Diffuseness degree of the T-to-C phase transition for the unpoled single crystal has been calculated to be 1.56, implying an intermediate state between normal and relaxor ferroelectrics. Temperature-dependent remanent polarization (Pr), coercive field (Ec), saturation polarization (Ps), hysteresis loop squareness (Rsq), and longitudinal piezoelectric constant (d* 33) are also explored to learn the details of the phase transitions. Variable temperature unipolar Suni-E hysteresis loops avail additional evidence for the microstructure change in the as-measured single crystal. Full article
(This article belongs to the Special Issue Piezoelectric Crystals)
Open AccessArticle Preparation and Characterization of Lead-Free (K0.5Na0.5)NbO3-LiNbO3 and (K0.5Na0.5)NbO3-LiTaO3 Ferroelectric Single Crystals
Crystals 2014, 4(3), 296-305; doi:10.3390/cryst4030296
Received: 20 April 2014 / Revised: 9 June 2014 / Accepted: 2 July 2014 / Published: 16 July 2014
Cited by 1 | PDF Full-text (12884 KB) | HTML Full-text | XML Full-text
Abstract
Lead-free (K0.5Na0.5)NbO3-LiNbO3 (KNN-LN) and (K0.5Na0.5)NbO3-LiTaO3 (KNN-LT) ferroelectric single crystals, with the dimensions of 11 ´ 11 ´ 5 mm3 and 5 ´ 5 ´ 3 mm3 [...] Read more.
Lead-free (K0.5Na0.5)NbO3-LiNbO3 (KNN-LN) and (K0.5Na0.5)NbO3-LiTaO3 (KNN-LT) ferroelectric single crystals, with the dimensions of 11 ´ 11 ´ 5 mm3 and 5 ´ 5 ´ 3 mm3, were grown successfully using the top-seeded solution growth (TSSG) method, respectively. The crystal structures were analyzed by means of X-ray diffraction, showing orthorhombic symmetry for KNN-LN single crystals and coexistence of orthorhombic and tetragonal symmetry for KNN-LT single crystals at room temperature. The orthorhombic-tetragonal (TO-T) and tetragonal-cubic (TC) phase transition temperatures are 195 °C and 420 °C for the KNN-LN single crystals, and 130 °C and 280 °C for KNN-LT single crystals, respectively. The remnant polarization (Pr) is 27.8 μC/cm2 with a coercive field (Ec) of 17 kV/cm for KNN-LT single crystals. The two single crystals showed 90° domains with layers in (parallel) straight lines, while KNN-LT single crystals have a larger domain region. The actual stoichiometry deviates easily from the original composition in the process of crystal growth, thus, an appropriate nominal composition and optimized crystal growth method is desired to get high-quality crystals in the future. Full article
(This article belongs to the Special Issue Piezoelectric Crystals)
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Open AccessArticle High-Q Defect-Free 2D Photonic Crystal Cavity from Random Localised Disorder
Crystals 2014, 4(3), 342-350; doi:10.3390/cryst4030342
Received: 21 May 2014 / Revised: 29 May 2014 / Accepted: 4 July 2014 / Published: 16 July 2014
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Abstract
We propose a high-Q photonic crystal cavity formed by introducing random disorder to the central region of an otherwise defect-free photonic crystal slab (PhC). Three-dimensional finite-difference time-domain simulations determine the frequency, quality factor, Q, and modal volume, V, of [...] Read more.
We propose a high-Q photonic crystal cavity formed by introducing random disorder to the central region of an otherwise defect-free photonic crystal slab (PhC). Three-dimensional finite-difference time-domain simulations determine the frequency, quality factor, Q, and modal volume, V, of the localized modes formed by the disorder. Relatively large Purcell factors of 500–800 are calculated for these cavities, which can be achieved for a large range of degrees of disorders. Full article
(This article belongs to the Special Issue Photonic Crystals)
Open AccessArticle Phase Energy Determined from Stress and Electric-Field-Induced Phase Transformations in [011]C Cut 0.24PIN-PMN-PT Single Crystals
Crystals 2014, 4(3), 377-389; doi:10.3390/cryst4030377
Received: 8 May 2014 / Revised: 15 July 2014 / Accepted: 5 August 2014 / Published: 19 August 2014
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Abstract
The effect of composition and temperature on the large field behavior of [011]C cut and poled (d32-mode) rhombohedral relaxor ferroelectric 0.24PIN-(1−x)PMN-xPT single crystals was characterized under electromechanical loading and the relative phase energy determined. [...] Read more.
The effect of composition and temperature on the large field behavior of [011]C cut and poled (d32-mode) rhombohedral relaxor ferroelectric 0.24PIN-(1−x)PMN-xPT single crystals was characterized under electromechanical loading and the relative phase energy determined. The electric field and stress induced polarization and strain response and field dependent material properties are reported for two concentrations of lead titanate (PT), with one PT concentration closer to the morphotropic phase boundary, at low and high temperature. A thermodynamic analysis to determine the relative energy levels of the rhombohedral and orthorhombic phases is based on the path integration of the measured data to determine external work done to drive the phase transition. The effect of heat generated by irreversible strain and electric displacement increments (hysteresis in the phase transformation) was removed from the work done during the loading cycle and the relative Helmholtz free energy density levels of the phases was determined. Full article
(This article belongs to the Special Issue Piezoelectric Crystals)
Open AccessArticle Modeling the Shape of Ions in Pyrite-Type Crystals
Crystals 2014, 4(3), 390-403; doi:10.3390/cryst4030390
Received: 13 April 2014 / Revised: 22 August 2014 / Accepted: 26 August 2014 / Published: 3 September 2014
Cited by 1 | PDF Full-text (596 KB) | HTML Full-text | XML Full-text
Abstract
The geometrical shape of ions in crystals and the concept of ionic radii are re-considered. The re-investigation is motivated by the fact that a spherical modelling is justified for p valence shell ions on cubic lattice sites only. For the majority of [...] Read more.
The geometrical shape of ions in crystals and the concept of ionic radii are re-considered. The re-investigation is motivated by the fact that a spherical modelling is justified for p valence shell ions on cubic lattice sites only. For the majority of point groups, however, the ionic radius must be assumed to be an anisotropic quantity. An appropriate modelling of p valence ions then has to be performed by ellipsoids. The approach is tested for pyrite-structured dichalcogenides MX2, with chalcogen ions X = O, S, Se and Te. The latter are found to exhibit the shape of ellipsoids being compressed along the <111> symmetry axes, with two radii r|| and r describing their spatial extension. Based on this ansatz, accurate interatomic MX distances can be derived and a consistent geometrical model emerges for pyrite-structured compounds. Remarkably, the volumes of chalcogen ions are found to vary only little in different MX2 compounds, suggesting the ionic volume rather than the ionic radius to behave as a crystal-chemical constant. Full article
Figures

Open AccessArticle Hexaethylguanidinium Salts
Crystals 2014, 4(3), 404-416; doi:10.3390/cryst4030404
Received: 14 July 2014 / Revised: 18 August 2014 / Accepted: 26 August 2014 / Published: 5 September 2014
Cited by 1 | PDF Full-text (9780 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Crystal structures of five hexaethylguanidinium salts (PF6 1, FeCl4 2, CuCl42−·H2O 3, CoBr42−/Br·H2O 4, bistriflimide 5) were determined. Short interionic contacts [...] Read more.
Crystal structures of five hexaethylguanidinium salts (PF6 1, FeCl4 2, CuCl42−·H2O 3, CoBr42−/Br·H2O 4, bistriflimide 5) were determined. Short interionic contacts were identified. Cyclic voltammetry of 2 revealed an electrochemical window from +1.0 to −1.5 V with a single Fe(III)/Fe(II) redox event at −0.27 V on a gold electrode versus Ag/AgCl. Full article
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Open AccessArticle Retrieval of Effective Parameters of Subwavelength Periodic Photonic Structures
Crystals 2014, 4(3), 417-426; doi:10.3390/cryst4030417
Received: 15 August 2014 / Revised: 3 September 2014 / Accepted: 3 September 2014 / Published: 17 September 2014
Cited by 1 | PDF Full-text (156 KB) | HTML Full-text | XML Full-text
Abstract
We revisit the standard Nicolson–Ross–Weir method of effective permittivity and permeability restoration of photonic structures for the case of subwavelength metal-dielectric multilayers. We show that the direct application of the standard method yields a false zero-epsilon point and an associated spurious permeability [...] Read more.
We revisit the standard Nicolson–Ross–Weir method of effective permittivity and permeability restoration of photonic structures for the case of subwavelength metal-dielectric multilayers. We show that the direct application of the standard method yields a false zero-epsilon point and an associated spurious permeability resonance. We show how this artifact can be worked around by the use of the cycle shift operator to the periodic multilayer in question. Full article
(This article belongs to the Special Issue Photonic Crystals)

Review

Jump to: Research

Open AccessReview Potential Advantage of Multiple Alkali Metal Doped KNbO3 Single Crystals
Crystals 2014, 4(3), 190-208; doi:10.3390/cryst4030190
Received: 1 April 2014 / Revised: 10 June 2014 / Accepted: 16 June 2014 / Published: 26 June 2014
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Abstract
Potassium niobate crystal KNbO3 (KN) is a well-known crystal for lead free piezoelectric or nonlinear optical applications. The KN crystal has been studied in both single crystal form and in thin film form which has resulted in many review articles being [...] Read more.
Potassium niobate crystal KNbO3 (KN) is a well-known crystal for lead free piezoelectric or nonlinear optical applications. The KN crystal has been studied in both single crystal form and in thin film form which has resulted in many review articles being published. In order to exceed the KN crystal, it is important to study KN phase forming and doping effects on the K site. This article summarizes the authors’ study towards a multiple alkali metal doped KN crystal and related single crystals briefly from the viewpoint of crystal growth. Full article
(This article belongs to the Special Issue Piezoelectric Crystals)
Open AccessReview Rare-Earth Calcium Oxyborate Piezoelectric Crystals ReCa4O(BO3)3: Growth and Piezoelectric Characterizations
Crystals 2014, 4(3), 241-261; doi:10.3390/cryst4030241
Received: 12 April 2014 / Revised: 15 June 2014 / Accepted: 24 June 2014 / Published: 8 July 2014
Cited by 2 | PDF Full-text (1180 KB) | HTML Full-text | XML Full-text
Abstract
Rare-earth calcium oxyborate crystals, ReCa4O(BO3)3 (ReCOB, Re = Er, Y, Gd, Sm, Nd, Pr, and La ), are potential piezoelectric materials for ultrahigh temperature sensor applications, due to their high electrical resistivity at elevated temperature, high piezoelectric [...] Read more.
Rare-earth calcium oxyborate crystals, ReCa4O(BO3)3 (ReCOB, Re = Er, Y, Gd, Sm, Nd, Pr, and La ), are potential piezoelectric materials for ultrahigh temperature sensor applications, due to their high electrical resistivity at elevated temperature, high piezoelectric sensitivity and temperature stability. In this paper, different techniques for ReCOB single-crystal growth are introduced, including the Bridgman and Czochralski pulling methods. Crystal orientations and the relationships between the crystallographic and physical axes of the monoclinic ReCOB crystals are discussed. The procedures for dielectric, elastic, electromechanical and piezoelectric property characterization, taking advantage of the impedance method, are presented. In addition, the maximum piezoelectric coefficients for different piezoelectric vibration modes are explored, and the optimized crystal cuts free of piezoelectric cross-talk are obtained by rotation calculations. Full article
(This article belongs to the Special Issue Piezoelectric Crystals)
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Open AccessReview Polarization Rotation and Monoclinic Distortion in Ferroelectric (Bi0.5Na0.5)TiO3–BaTiO3 Single Crystals under Electric Fields
Crystals 2014, 4(3), 273-295; doi:10.3390/cryst4030273
Received: 1 May 2014 / Revised: 26 June 2014 / Accepted: 27 June 2014 / Published: 16 July 2014
Cited by 6 | PDF Full-text (4648 KB) | HTML Full-text | XML Full-text
Abstract
The features of the crystal structures and spontaneous polarization (Ps) under an electric field (E) have been reviewed for (1 − x)(Bi0.5Na0.5)TiO3xBaTiO3 (BNT–BT). In-situ measurements of high-resolution [...] Read more.
The features of the crystal structures and spontaneous polarization (Ps) under an electric field (E) have been reviewed for (1 − x)(Bi0.5Na0.5)TiO3xBaTiO3 (BNT–BT). In-situ measurements of high-resolution synchrotron radiation X-ray diffraction (SR-XRD) under electric fields show that single crystals with x = 0 (BNT) and 5% have a monoclinic distortion in space group Cc at 25 °C. The SR-XRD study combined with density functional theory (DFT) calculations demonstrates that BNT–5%BT exhibits a rotation of Ps in the monoclinic ac plane by 2° under an E of 70 kV/cm along the <001> pseudo-cubic direction, which is much larger than BNT. Full article
(This article belongs to the Special Issue Piezoelectric Crystals)
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Open AccessReview Advances in the Growth and Characterization of Relaxor-PT-Based Ferroelectric Single Crystals
Crystals 2014, 4(3), 306-330; doi:10.3390/cryst4030306
Received: 29 April 2014 / Revised: 7 May 2014 / Accepted: 4 June 2014 / Published: 16 July 2014
Cited by 4 | PDF Full-text (3842 KB) | HTML Full-text | XML Full-text
Abstract
Compared to Pb(Zr1−xTix)O3 (PZT) polycrystalline ceramics, relaxor-PT single crystals offer significantly improved performance with extremely high electromechanical coupling and piezoelectric coefficients, making them promising materials for piezoelectric transducers, sensors and actuators. The recent advances in crystal [...] Read more.
Compared to Pb(Zr1−xTix)O3 (PZT) polycrystalline ceramics, relaxor-PT single crystals offer significantly improved performance with extremely high electromechanical coupling and piezoelectric coefficients, making them promising materials for piezoelectric transducers, sensors and actuators. The recent advances in crystal growth and characterization of relaxor-PT-based ferroelectric single crystals are reviewed in this paper with emphases on the following topics: (1) the large crystal growth of binary and ternary relaxor-PT-based ferroelectric crystals for commercialization; (2) the composition segregation in the crystals grown from such a solid-solution system and possible solutions to reduce it; (3) the crystal growth from new binary and ternary compositions to expand the operating temperature and electric field; (4) the crystallographic orientation dependence and anisotropic behaviors of relaxor-PT-based ferroelectriccrystals; and (5) the characterization of the dielectric, elastic and piezoelectric properties of the relaxor-PT-based ferroelectriccrystals under small and large electric fields. Full article
(This article belongs to the Special Issue Piezoelectric Crystals)
Open AccessReview Growth and Characterization on PMN-PT-Based Single Crystals
Crystals 2014, 4(3), 331-341; doi:10.3390/cryst4030331
Received: 1 May 2014 / Revised: 2 July 2014 / Accepted: 3 July 2014 / Published: 16 July 2014
Cited by 3 | PDF Full-text (10872 KB) | HTML Full-text | XML Full-text
Abstract
Lead magnesium niobate—lead titanate (PMN-PT) single crystals have been successfully commercialized in medical ultrasound imaging. The superior properties of PMN-PT crystals over the legacy piezoelectric ceramics lead zirconate titanate (PZT) enabled ultrasound transducers with enhanced imaging (broad bandwidth and improved sensitivity). To [...] Read more.
Lead magnesium niobate—lead titanate (PMN-PT) single crystals have been successfully commercialized in medical ultrasound imaging. The superior properties of PMN-PT crystals over the legacy piezoelectric ceramics lead zirconate titanate (PZT) enabled ultrasound transducers with enhanced imaging (broad bandwidth and improved sensitivity). To obtain high quality and relatively low cost single crystals for commercial production, PMN-PT single crystals were grown with modified Bridgman method, by which crystals were grown directly from stoichiometric melt without flux. For ultrasound imaging application, [001] crystal growth is essential to provide uniform composition and property within a crystal plate, which is critical for transducer performance. In addition, improvement in crystal growth technique is under development with the goals of improving the composition homogeneity along crystal growth direction and reducing unit cost of crystals. In recent years, PIN-PMN-PT single crystals have been developed with higher de-poling temperature and coercive field to provide improved thermal and electrical stability for transducer application. Full article
(This article belongs to the Special Issue Piezoelectric Crystals)
Open AccessReview Relaxor-PT Single Crystal Piezoelectric Sensors
Crystals 2014, 4(3), 351-376; doi:10.3390/cryst4030351
Received: 1 June 2014 / Revised: 8 July 2014 / Accepted: 14 July 2014 / Published: 28 July 2014
Cited by 3 | PDF Full-text (2524 KB) | HTML Full-text | XML Full-text
Abstract
Relaxor-PbTiO3 piezoelectric single crystals have been widely used in a broad range of electromechanical devices, including piezoelectric sensors, actuators, and transducers. This paper reviews the unique properties of these single crystals for piezoelectric sensors. Design, fabrication and characterization of various relaxor-PT [...] Read more.
Relaxor-PbTiO3 piezoelectric single crystals have been widely used in a broad range of electromechanical devices, including piezoelectric sensors, actuators, and transducers. This paper reviews the unique properties of these single crystals for piezoelectric sensors. Design, fabrication and characterization of various relaxor-PT single crystal piezoelectric sensors and their applications are presented and compared with their piezoelectric ceramic counterparts. Newly applicable fields and future trends of relaxor-PT sensors are also suggested in this review paper. Full article
(This article belongs to the Special Issue Piezoelectric Crystals)

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