Strontium Barium Niobate Crystal Research Articles

Влияние примеси тулия на диэлектрические и пироэлектрические свойства монокристаллов ниобата бария стронция

It has been shown that the introduction of thulium impurity into the crystals of strontium barium (SBN:61) niobate leads to an increase in the dielectric constant value and the blur region of the phase transition. External field polarization partially stabilizes the polar state of the samples, however, the heterogeneous distribution of polarization across the thickness of the studied samples indicates the existence of regions with a developed domain structure characteristic of highly doped crystals.

Influence of thulium impurity on dielectric and pyroelectric properties of single crystals of Barium Strontium Niobate

It has been shown that the introduction of thulium impurity into the crystals of strontium barium (SBN : 61) niobate leads to an increase in the dielectric constant value and the blur region of the phase transition. External field polarization partially stabilizes the polar state of the samples, however, the heterogeneous distribution of polarization across the thickness of the studied samples indicates the existence of regions with a developed domain structure characteristic of highly doped crystals. Keywords: Ferroelectrics, relaxors, pyroelectric effect, polarization distribution, single crystal, SBN.

Scattered Image Reconstruction at Near-Infrared Based on Spatial Modulation Instability

We present a method of near-infrared image reconstruction based on spatial modulation instability in a photorefractive strontium barium niobate crystal. The conditions that lead to the formation of modulation instability at near-infrared are discussed depending on the theory of modulation instability gain. Experimental results of scattered image reconstruction at the 1064 nm wavelength show the maximum cross-correlation coefficient and cross-correlation gain are 0.57 and 2.09 respectively. This method is expected to be an aid for near-infrared imaging technologies.

Strontium barium niobate crystals with various chemical compositions probed by Raman and Brillouin scattering

The Sr x Ba1 – x Nb2O6 crystals with x = 0.33, 0.5, 0.61, 0.75 were studied by Raman and Brillouin light scattering in a wide temperature range. The experimental temperature dependences of the central peak's integral intensity and the position and width of the longitudinal acoustic mode were plotted using derivative analysis. It is shown that the temperature at which the abnormal behavior begins (the so-called Burns temperature) is only slightly different for all the crystals under study, while the phase transition temperatures differ significantly. It allows asserting the identical microscopic nature of the Burns temperature in Sr x Ba1 – x Nb2O6 crystals.

Evolution of the domain structure during polarization reversal in relaxor SBN single crystals studied by Čerenkov-type second harmonic generation microscopy

The evolution of the domain structure during polarization reversal in single crystals of a relaxor ferroelectric strontium-barium niobate (Sr0.61Ba0.39Nb2O6) doped with 0.05 wt.% Ni2O3 was investigated. The domains in the crystal bulk were imaged by Čerenkov-type second harmonic generation microscopy. Three types of domains were revealed: (1) domains with a broad boundary, (2) cylindrical domains, and (3) conical domains. Three stages of the domain shape evolution were distinguished in the domain with a broad boundary. The velocities of the sideways wall motion and forward domain growth were measured for all the domain types.

Propagation of the first order annular Bessel Gaussian beams in a uniaxial crystal along the optical axis governed by the Pockels effect.

We investigate the first order annular Bessel Gaussian beams propagating in a strontium barium niobate (SBN) crystal governed by the Pockels effect. The left-hand circularly polarized incident waves propagating along the optical axis in the crystal give rise to the right-hand circularly polarized vortex fields with a topological charge of 2. If an external dc field is applied along the optical axis of the SBN crystal, the anisotropy strength can be controlled rapidly, and the rotational invariance around the optical axis is still maintained. In this case, the normalized intensity in the focal region, the power exchange between left-hand and right-hand components, and the exchange between the spin and orbit contributions of the angular momentum flux can be manipulated. We also consider the case where the incident waves are linearly polarized along the x axis. The cylindrical symmetry of two Cartesian components is broken during propagation due to the anisotropy, and the intensity distribution as well as the polarization state of the beams can be regulated electrically.

Temperature dependence of the spontaneous polarization, acoustic and strain anomalies in strontium barium niobate crystals of different chemical compositions probed by the second harmonic generation technique

In SrxBa1−xNb2O6 crystals (x = 0.33, 0.5, 0.61, and 0.75), temperature dependences of spontaneous polarization, strain, elastic modules, and second harmonic generation (SHG) signal are compared. It is revealed that SHG describes the temperature dependences of dipole moments in polar nanoregions in paraelectric phase. In the vicinity of the phase transition in paraelectric phase, SHG reflects the temperature behavior of relatively large and long-lived polar asymmetric regions as indicated by the presence of the intermediate temperature range on the temperature dependence of this nonlinear response.

Optical investigations of fluctuation of order parameter in THz range in SrxBa1-xNb2O6 crystals with different chemical compositions

Low-frequency spectra are investigated in a series of strontium barium niobate crystals SrxBa1-xNb2O6 with chemical compositions x = 0.33, 0.5, 0.61, and 0.75 in a back-scattering (ZZ) geometry and a wide temperature range including ferroelectric and paraelectric phases. It is shown that for all crystals studied, a central peak (CP) is clearly manifested in the vicinity of phase transition temperature. The temperature dependences of the CP parameters were obtained in all investigated crystals. It is shown that the central peak in all crystals studied is described by a number of relaxation times, which is typical for relaxors.

Dynamics of mesoscopic polarization in the uniaxial tetragonal tungsten bronze (SrxBa1−x)Nb2O6

The high-frequency dielectric behavior of uniaxial tungsten-bronze strontium barium niobate crystals with various Sr/Ba ratios, including both ferroelectric and relaxor compositions, have been studied in a broad frequency range (${10}^{4}$ to ${10}^{13}\phantom{\rule{0.16em}{0ex}}\mathrm{Hz}$) and temperature interval 100--500 K in order to thoroughly understand the evolution of the relaxation dynamics across the ferroelectric phase transition. The dielectric response along the polar axis consists of three relaxations corresponding to polarization mechanisms related to several correlation lengths of mesoscopic order. All of them show dissimilar behaviors with temperature, pointing out to their distinct nature. A temperature-dependent central mode at THz frequencies and a relaxation above 10 GHz are accompanied by the slowing down of a relaxation in the MHz range. This response reveals the complex mechanism of the phase transition and supports the coexistence of displacive and order-disorder scenarios. Relaxor and ferroelectric compositions surprisingly reveal similar qualitative behavior within the frequency window used. However, relaxor crystals display relaxations at higher frequency because of the smaller extent of the polar fluctuations and ferroelectric regions, which coexist in almost all the compositions. The presence of two different ferroelectric subsystems in the structure agrees with the existence of several polarization mechanisms involved in the complex dielectric and ferroelectric response.

Dependence of acoustic anomalies on chemical composition in strontium barium niobate crystals (from conventional ferroelectric to relaxor) probed by Brillouin light scattering

Brillouin spectra in a series of strontium barium niobate crystals SrxBa1-xNb2O6 of different chemical composition (x = 0.3, 0.5, 0.6, 0.75) are investigated in various spectral geometries and in a wide temperature ranges including ferroelectric and paraelectric phases. It is shown that for all crystals studied, a pronounced temperature dependences of position and width of the Brillouin lines are clearly manifested only when the acoustic wave vector is parallel to the polar axis Z. Exponential temperature dependence of anomalies of elastic modules was obtained. The exponent rate decreases with increasing of disordering in crystals under study.

Local switching in SBN:Ni single crystals with various initial domain states

ABSTRACTWe present the results of experimental study of the local switching in single crystals of relaxor ferroelectric Ni-doped strontium barium niobate with various initial domain states using conductive tip of scanning probe microscope. We investigated the domain growth in as-grown domain structure and initial domain states created by: (i) scanning by biased tip, (ii) in-field cooling, and (iii) scanning by electron beam. The dependences of effective domain radius on the voltage and pulse duration were derived. The shape factor, domain wall mobility, and start voltage were revealed. The obtained results can be used for the domain engineering in ferroelectrics.

Fast polarization mechanisms in the uniaxial tungsten-bronze relaxor strontium barium niobate SBN-81

The high-frequency dielectric response of the uniaxial strontium barium niobate crystals with 81% of Sr has been studied from 1 kHz to 30 THz along the polar c axis by means of several techniques (far infrared, time domain terahertz, high-frequency and low-frequency dielectric spectroscopies) in a wide temperature interval 20–600 K. Relaxor properties were observed in the complex dielectric response and four main excitations were ascertained below the phonon frequencies. These fast polarization mechanisms take place at THz, GHz and MHz ranges and show different temperature evolution. The central mode excitation in the THz range, related to anharmonic dynamics of cations, slightly softens from high temperatures and then hardens below T ~ 400 K. Below the phase transition (at T ~ 330 K) an additional microwave excitation appears near 10 GHz related to micro domain wall oscillations. The strongest relaxation appears in the GHz range and slows down on cooling according to the Arrhenius law. Finally, another relaxation, present in the MHz range at high temperatures, also slows down on cooling at least to the kHz range. These two relaxations are due to polar fluctuations and nanodomains dynamics. Altogether, the four excitations explain the dielectric permittivity maximum in the kHz range.

Coaxial random-access reading in multilayered optical data storage systems using a pair of counter-propagating pulse-shaped spatial solitons

Coaxial random-access reading in multilayered optical data storage using a pair of counter-propagating pulse-shaped spatial solitons was experimentally investigated. Counter-propagating second-harmonic spatial solitons, which are formed by focusing titanium sapphire pulsed lasers, induced nonlinear collision and determined the depth readout address in a strontium barium niobate crystal. The nonlinear interaction between the collision and the locally-reversed crystal domains, which represents single-bit data, changed the spectrum and intensity of the transmitted second-harmonic beam. Coaxial random-access reading associated with the spatial soliton of the multilayered bit datum was demonstrated by scanning collision points along the direction of the depth.

Modulation instability of broad optical beams in unbiased photorefractive pyroelectric crystals

We present a study of the one dimensional modulation instability due to a broad optical beam in pyroelectric photorefractive crystals where the space charge field is formed due to solely the pyrolectric effect. The one-dimensional growth rate of the modulation instability depends upon the intensity of the incident beam and the magnitude of the temperature change. Relevant example of a Strontium Barium Niobate crystal is taken to illustrate the theoretical analysis.

Structure and real composition of undoped and Cr- and Ni-doped Sr0.61Ba0.39Nb2O6 single crystals

Strontium barium niobate crystals with congruent melting composition Sr0.61Ba0.39Nb2O6 (SBN-61), both nominally pure and doped with Cr3+ и Ni3+ ions, have been investigated by neutron diffraction. Different strontium and barium contents as well as their different distribution over the Sr1, of Sr2 and Ba2 crystallographic sites of SBN-61 structure, caused by introduction of dopants, have been revealed. Coordination polyhedra of cations have been established based on the analysis of cation–anion internuclear distances together with the calculation of bond-valence sums for cations, which are equal to their formal charge. It was found that the Nb1 and Nb2 atoms are located in distorted octahedra with quadfurcated (the Nb1O6 polyhedron) or bifurcated (the Nb2O6 polyhedron) vertices, and the Sr1 atoms are located in a cuboctahedron with bifurcated vertices in the base plane. Different polyhedra have been revealed for the Sr2 and Ba2 atoms: Sr2 atoms are coordinated by 15 oxygen atoms to form a highly distorted five-capped pentagonal prism, whereas Ba2 atoms are located in a highly distorted three-capped trigonal prism with a coordination number 9. Comparison of interatomic and internuclear distances, determined by X-ray and neutron diffraction analyses, respectively, allowed to reveal a highly pronounced shift of electron density in Nb1 and Sr2 polyhedra, responsible for the covalent bond and properties of crystals. Location of Cr3+ и Ni3+ dopant ions in the SBN-61 structure as well as their formal charges has been discussed.

Spectroscopic ellipsometry technique as a materials characterization tool for mechatronic systems—The case of composition and doping concentration monitoring in SBN crystals

The paper aims to provide spectroscopic ellipsometry technique as a tool for sensor materials studies. The principles of measurement, the ellipsometric data evaluation and the standard rotating analyzer configuration of the ellipsometric instrument are introduced. The possibilities and the limitations of spectroscopic ellipsometry technique for material studies attractive from the point of view of optoelectronic sensors and micro electro-mechanical sensors and actuators applications are discussed. Studies of composition and the Ce3+ doping level for ferroelectric strontium barium niobate crystals are presented as an example of possible non-straightforward application of this technique.

Arrays of Gaussian vortex, Bessel and Airy beams by computer-generated hologram

We generate various kinds of arrays of Gaussian vortex, Bessel and Airy beams, respectively, with digital phase holograms (DPH) based on the fractional-Talbot effect by using the phase-only spatial light modulator (SLM). The linear and nonlinear transmissions of these beam arrays in strontium barium niobate (SBN) crystal are investigated numerically and experimentally. Compared with Gaussian vortex arrays, Bessel and Airy beam arrays can keep their patterns unchanged in over 20mm, realizing non-diffracting transmission. The Fourier spectra (far-field diffraction patterns) of the lattices are also studied. The experimental results are in good agreement with the numerical simulations.

Ultrashort pulse chirp measurement via transverse second-harmonic generation in strontium barium niobate crystal

Pulse compression in dispersive strontium barium niobate crystal with a random size and distribution of the anti-parallel orientated nonlinear domains is observed via transverse second harmonic generation. The dependence of the transverse width of the second harmonic trace along the propagation direction allows for the determination of the initial chirp and duration of pulses in the femtosecond regime. This technique permits a real-time analysis of the pulse evolution and facilitates fast in-situ correction of pulse chirp acquired in the propagation through an optical system.

Non-collinear generation of the second optical harmonic in strontium-barium niobate crystals with needle-like microdomains

The structure of the spatial spectra from the second harmonic (SH) of yttrium-aluminum-garnet neodymium laser radiation during quasi-phase-matched generation is studied in a spatially inhomogeneous nonlinear medium. Based on the example of the formation of the strontium-barium niobate (SBN) domain structure a theoretical model that describes the angular distribution of the intensity of the noncollinear SH generated in the polydomain crystal with stochastically distributed domains is proposed. It is shown that the characteristic spatial domain sizes can be found from the second-harmonic intensities and that the density of the domain distribution is described by the Weibull-Gnedenko distribution.

Calcium barium niobate as a functional material for broadband optical frequency conversion

We demonstrate the application of as-grown calcium barium niobate (CBN) crystal with random-sized ferroelectric domains as a broadband frequency converter. The frequency conversion process is similar to broadband harmonic generation in commonly used strontium barium niobate (SBN) crystal, but results in higher conversion efficiency reflecting a larger effective nonlinear coefficient of the CBN crystal. We also analyzed the polarization properties of the emitted radiation and determined the ratio of d32 and d33 components of the second-order susceptibility tensor of the CBN crystal.