Potassium Niobate Single Crystals Research Articles

Growth and characterization of sodium potassium niobate single crystals near morphotropic phase boundaries

By using a high-temperature solution approach, lead-free single crystals of sodium potassium niobate Kx Na(1-x)NbO3 have been grown at three different phase boundary compositions (x = 0.17, 0.35, and 0.50). The monoclinic and orthorhombic crystal structures are present in the compositions × = 0.17 and × = 0.50 related crystal structures. Ferroelectricity is induced at lower temperatures and requires a smaller critical electric field when KNbO3 content is included into NaNbO3 crystals. Studies using the scanning electron microscope (SEM) and atomic force microscope (AFM) have shown how the sodium potassium niobate (KNN) crystals grow morphologically. With an increase in potassium concentration in the KNN system, the average step size falls. KNN crystals were subjected to impedance analyzer-based dielectric investigations. With an increase in concentration, a decrease in dielectric loss was found. The compositions with potassium concentrations of x = 0.50, 0.35, and 0.17 were found to have piezoelectric coefficients (d33) of 72 pC/N, 63 pC/N, and 52 pC/N, respectively.

Growth of lithium niobate and potassium niobate single crystals using the Czochralski method with liquid and ceramic charging

Lithium niobate and potassium niobate crystals of near-stoichiometric composition were grown with the help of the Czochralski method with liquid and ceramic charging. Birefringence of the grown lithium niobate sample is Δn = 1.5 at 1 THz frequency, pleochroism in absorption on 1 THz frequency makes preferable the using of the extraordinary wave because of the lower absorption coefficient (14 cm−1). The absorption coefficient for the grown crystal of potassium niobate is 24 cm−1 at 1 THz frequency.

Characterization of the Electro-Optic Modulation Properties of a yz-Cut Potassium Niobate Single Crystal

We theoretically investigate the electro-optic (EO) effect in a yz-cut potassium niobate (KNbO3, KN) single crystal when a direct-current (DC) electric field is applied in the direction of [101]. We derived an analytical expression describing the change in the index ellipsoid under the applied DC electric field and solved its characteristic equation to obtain the refractive-index change induced by the EO effect. In order to show the practicality of our approach, we consider a classic application of the technique — an integrated Mach-Zehnder (MZ) modulator used for optical communication systems. The phase- and the intensity-modulation properties of the KN MZ modulator are discussed in detail, and all simulation results are compared with those for the lithium niobate (LN) counterpart that are widely used in current optical infrastructures. The results show that smaller-size or lower power-consuming EO modulators are feasible based on the proposed KN scheme due to its higher modulation efficiency.

Dielectric dispersion in pure, samarium, samarium & tin doped potassium niobate single crystals

Dielectric properties were studied; using a LCR tester at varies temperatures, from 50 Hz to 100 KHz for pure, samarium, samarium & tin doped potassium niobate single crystals. Due to samarium doping change in the dielectric constant and dielectric losses are attributed to domain walls and Maxwell Wagner type respectively.

Pyroelectric study of pure, rare earth and metal doped potassium niobate single crystals

ABSTRACTPure, rare earth Sm3+-doped, Sm3+ and metal Sn4+doped ferroelectric single crystals were grown by controlled cooling of the melt. The crystals were characterized for their pyroelectric behavior over a temperature range of 303 K to 773K. The pyroelectric coefficient shows an anomaly around expected transition temperature. The pyroelectric coefficient also show a change in polarity. The mechanism of pyroelectricity in these grown materials is discussed considering the pyroelectric figure of merit (PFM).

Bridgman growth and luminescence properties of dysprosium doped lead potassium niobate crystal

Dy-doped lead potassium niobate (Pb2KNb5O15, PKN) single crystal was grown by the modified vertical Bridgman method through spontaneous nucleation. The crystal was brownish, transparent and inclusion free. Five excitation peaks of Dy3+ ions were clearly seen from near ultraviolet region to blue range. It was unique that the excitation peaks in blue range were more intense, especially the one centered at 455nm. The emission bands consisted of blue, yellow and red emissions, which were at about 487nm, 573nm and 662nm respectively. The CIE chromaticity diagram of PKN:Dy indicated that white light and yellow light could be emitted when the crystal was excited under near ultraviolet light and blue light, respectively. Thus PKN:Dy crystal is a candidate material whose emitting light could be tunable through changing the excited light wavelength.

Method of manufacturing potassium niobate single crystal thin film, surface acoustic wave element, frequency filter, frequency oscillator, electronic circuit, and electronic apparatus

A method of manufacturing potassium niobate single crystal thin film on a single crystal substrate that epitaxially grows orthorhombic potassium niobate single crystal at a temperature near room temperature at a high deposition rate. A surface acoustic wave element, frequency filter, frequency oscillator, electronics circuit, and electronic device employ the thin film manufactured by the method, and are high in k 2 , wideband, downsized, and economical in power consumption. The method includes the steps of coating liquid drops of a potassium niobate solution on a SrTiO 3 single crystal substrate by a liquid drop emission method, and precipitating potassium niobate single crystal layer by epitaxial growth from the liquid drops.

Introduction of Fine Engineered Domain Configuration into Potassium Niobate Single Crystals

To induce fine engineered domain configurations into potassium niobate (KNbO3) single crystals, two kinds of methods were performed, i.e., (1) high DC electric field exposure along the opposite direction of polarization of KNbO3 single-domain crystals at room temperature, and (2) introduction of randomly oriented fine domain configuration by heat treatment at 700 °C and then high DC electric field exposure along [001]c direction of KNbO3 multidomain crystals at room temperature. When the method (1) was performed, finally, the poled KNbO3 crystals became to single-domain state again through the formation of multidomain state. On the other hand, the KNbO3 multidomain crystals were obtained by using the method (2), and an enhancement of piezoelectric-related properties was observed.

Growth and characterization of reduced and unreduced Rh doped potassium niobate single crystals

Rh doped potassium niobate single crystals are grown by the high-temperature solution growth (HTSG) method with a melt doping level of 1500 mg/g. The crystals are reduced to different levels by subjecting them to an in situ high-temperature reduction under an oxygen-deficient atmosphere followed by fast cooling. The characterization results indicate a segregation coefficient of slightly less than 1% for rhodium. The high-resolution X-ray diffraction studies reveal only a slight broadening for reduced crystals, indicating that the reduction process does not deteriorate strongly the crystalline perfection. Loss of an oxygen atom by formation of an oxygen vacancy accompanied by releasing two electrons is identified as the most likely defect mechanism for the reduction, which results in a lower valence of Rh in the lattice and appears a strong change in the absorption spectrum. The reduction is also accompanied by a loss of hydrogen that leads to a decrease of the infrared (IR) vibrational bonds associated to the OH complex. Two-wave mixing measurements show that majority charge carriers for highly reduced crystals change from holes in unreduced crystals to electrons in reduced crystals at longer wavelength (>580 nm).

Domain Wall Engineering in Potassium Niobate Single Crystals and Their Piezoelectric Properties

For potassium niobate (KNbO3) single crystal, the 31 resonators with the highest piezoelectric constant d31 were designed using transformation of axis. We confirmed that the engineered domain configurations with maximum d31 of –55.1 pC/N was caused by a combination between two polarization with polar directions along [101]c and [-101]c directions. Moreover, if there are larger piezoelectric constants from domain wall region, we can expect the much higher piezoelectric properties. To induce the above domain configuration, a new poling method using patterning electrode was investigated. In this study, the two methods on the basis of temperature-induced phase transition at 207 °C and electric-field-induced phase transition at room temperature were investigated.

Preparation of Potassium Niobate Crystals with Fine Engineered Domain Configurations and Their Enhanced Piezoelectric Properties

Potassium niobate (KNbO 3 ) single crystals were grown by a top-seeded solution growth (TSSG) method. At first, the electric field was applied along [001]c (cubic notification system) direction of KNbO 3 crystals to induce the engineered domain configurations into KNbO 3 crystals. Prior to domain engineering, the piezoelectric properties of [001]c oriented KNbO 3 single-domain crystals were measured. These measurement values were completely consisted with the calculated d 31 and d 32 . Finally, the fine engineered domain configurations were induced into KNbO 3 crystals. As a result, piezoelectric properties increased with decreasing domain sizes of the engineered domain configuration. However, the symmetry of the KNbO 3 crystals was, and there were four kinds of domain structures such as 90°, 180°, 60° and 120° domains. Thus, the engineered domain structure induced in this study was very complicated structure, and the piezoelectric properties were also depended on domain pattern and kinds of domain walls.

Enhanced piezoelectric properties of potassium niobate single crystals with fine engineered domain configurations

Potassium niobate (KNbO 3) single crystals were grown by a top seed solution growth (TSSG) method. At first, the electric field was applied along [0 0 1] c (cubic notification system) direction of KNbO 3 crystals to induce the engineered domain configurations into KNbO 3 crystals. Prior to domain engineering, the piezoelectric properties of [0 0 1] c oriented KNbO 3 single-domain crystals were measured. These measured values were completely consistent with the calculated apparent d 31 and d 32. Finally, the engineered domain configurations were induced into KNbO 3 crystals. As a result, piezoelectric properties increased with decreasing domain sizes of the engineered domain configuration.

Enhanced Piezoelectric Properties of Potassium Niobate Single Crystals by Domain Engineering

The engineered domain configuration was induced into potassium niobate (KNbO3) crystals, and the piezoelectric properties were investigated as a function of domain size. First, single-domain treatment was investigated, and a combination of chemical etching and 2-step electric poling treatment was effective. Using the single-domain crystals, all piezoelectric related constants were determined. On the basis of these piezoelectric constants, the d31 and d32 surfaces were calculated. The piezoelectric properties of [001]c oriented KNbO3 single-domain crystals were measured and were completely consistent with the calculated properties. Finally, the engineered domain configurations were induced into KNbO3 crystals by the control of the temperature and the electric-field along the [001]c direction. The piezoelectric properties of these KNbO3 crystals with the engineered domain configurations showed much higher values than those of the single-domain crystal. Moreover, the piezoelectric properties increased with decreasing the domain sizes of the engineered domain configuration.

Introduction of fine engineered domain configurations into potassium niobate single crystal and their piezoelectric properties

Introduction of fine engineered domain configurations into potassium niobate single crystal and their piezoelectric properties

Two-beam coupling measurements of anisotropic volume gratings in chromium-doped potassium niobate crystal

Abstract Empty traps concentration, the sign of the dominant photocarriers and the effective electro-optic coefficient in chromium doped potassium niobate single crystal using steady-state beam coupling at 532 nm, have been measured. A density of 0.7×10 −16 cm −3 of positive photocarriers, r eff =20 pm/V and 〈 κ 〉=0.25 are obtained. To explain these results, anisotropic photoexcitation cross section of mobile charge carriers has to be considered.

Poling Treatment and Piezoelectric Properties of Potassium Niobate Ferroelectric Single Crystals

Piezoelectric properties of potassium niobate (KNbO3) single crystals were investigated as a function of crystallographic orientations, i.e., [110]c of polar direction and [001]c of nonpolar direction. Prior to the piezoelectric measurements, the optimum conditions for a conventional poling method were investigated, and it was found that the optimum conditions for a conventional poling method were as follows, i.e., (a) high temperature above 100°C, (b) long soaking time over 1 h, (c) slow heating and cooling rates below 1°C/min, and (d) lower poling current below 1 µA. However, fully poled KNbO3 crystals were not obtained using the conventional poling method. Thus, to achieve fully poled KNbO3 single crystals, a new 2-step poling method was proposed. This method is composed of 2 poling stages, i.e., the 1st step for non-180° domain switchings at higher temperatures under a low DC bias field, and the 2nd step for 180° domain switchings at lower temperatures under a high DC bias field. Using the 2-step poling method, KNbO3 crystals were successfully poled, and then, their piezoelectric properties of k31 modes were measured using a resonance method. The [110]c poled KNbO3 crystals exhibited electromechanical coupling factor k31 of 28.9% and piezoelectric constant d31 of 18.4 pC/N while the [001]c poled KNbO3 crystals exhibited k31 of 31.2% and d31 of 51.7 pC/N. The piezoelectric constant d31 along nonpolar [001]c direction was 2.8 times higher than that along polar [110]c direction.

Characteristics of acoustic plate waves in potassium niobate (KNbO 3) single crystal

This paper presents detailed theoretical investigation of three fundamental acoustic wave modes propagating in thin plates of single crystal potassium niobate. The wave velocity and Δv/ v, the fractional velocity change produced by electrical shorting of the surface, are calculated for all propagation directions on the surfaces of X-, Y-, and Z-cut plates. It is found that acoustic plate waves can provide extremely large values of electromechanical coupling coefficient. This property makes these waves very attractive for use in a variety of sensor and signal processing applications.

Growth and characterisation of KNbO2 single crystals

The growth of good quality colourless potassium niobate (KNbO3) single crystals is reported. Various flux compositions with corresponding starting temperatures were chosen from the phase diagram to avoid the black/blue colour formation in growth of KNbO3 single crystals. Deviation of compositions of colourless and black crystals from the starting composition were analysed by electron spectroscopy for chemical analysis. Dielectric constant and pyroelectric coefficients were calculated with respect to temperature and the transition temperature was confirmed by differential scanning calorimetry studies. Hysteresis loops have been traced with respect to electric field.

Growth kinetic study of potassium niobate single crystal: a new method for high time-resolution kinetic data of ABO3-type materials

A new method to obtain high time-resolution kinetic data has been introduced in conjunction with a directional growth of KNbO3 single crystal. Using the step-growth on a selected (1 0 0)pc plane, experimental conditions such as solid-liquid-vapour meniscus, solute concentration, and temperature, can be well defined for the kinetic data. Due to the selective growth employed, the growth data account truly for a crystallographic plane of interest. Because the grown steps serve as a time marker, the volume of step can be measured and assigned to a respective growth whose time resolution achieved in this study is 8.4 s. In addition, using the current method, sequential growth events can be conducted with variable pulling rates to abstract different growth information. Small growth perturbation can also be recorded sensitively, as evidenced in the growth oscillation observed. Based on these findings, it is suggested that the method can be employed to other oxide perovskite ABO3 single crystal growths. Future applications and investigations are also proposed.

Top seeded solution growth of Rb-doped KNbO 3 single crystals

We report the growth of Rb-doped potassium niobate (KRN) single crystals using the top seeded solution growth (TSSG) technique. Colorless and transparent KRN single crystals have been successfully grown from melt comprising up to 15 mol% of Rb. Atomic absorption measurements indicate that the Rb content in the KRN solid solution is rather low, the Rb segregation coefficient being on the order of 0.05. Based on crystal energy considerations, the most probable Rb location in the host lattice is expected to be the lattice site of the K + cation. It is believed that the substitution of K + by a much larger Rb + has given rise to a lattice misfit in the doped bulk crystal, and thereby increased the total free energy of the crystal. From the thermodynamics point of view, the segregation phenomenon tends to reduce the lattice strain within the bulk crystals, hence, resulting in the segregation coefficient of Rb being rather small.