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[Display omitted] • Two competing processes are identified during the annealing process. • The emergence of void string offers a path for designing nanoscale exfoliation. • The mechanical property evolution is affected by the annealing process. The evolution of the microstructure and mechanical properties of low-energy heavy-ion-irradiated LiTaO 3 crystals annealed at various temperatures was investigated by transmission electron microscopy (TEM) observations and nanoindentation tests to extend the applications of irradiated LiTaO 3 crystals. Before annealing, randomly distributed voids formed in an approximately 200 nm thick region at the end of the ion irradiation range, which was attributed to preferential absorption of interstitials by the amorphous-crystalline interface. After annealing, a new directional diffusion path of defects was identified, resulting in a void string. Furthermore, void string diffusion to the free surface was also found during the annealing temperature increase process, which offers a potential application in designing custom sized-thickness exfoliation at the nanoscale. Meanwhile, two competing processes were identified during the annealing process: epitaxial recrystallization from the amorphous-crystalline interface and grain nucleation process in the amorphous region, which formed phases different from the matrix crystal structure, resulting in an interaction between them. Furthermore, the hardness of irradiated samples was also found to be affected by the annealing process; in particular, a hardness decrease induced by the interstitial Fe ions in the recrystallized region was also confirmed, which can improve the processability of samples for further application. [ABSTRACT FROM AUTHOR]

Pyroelectricity is a phenomenon when electricity is generated upon the detection of temperature change. The pyroelectric effect occurs when spontaneous polarization changes result in charge accumulation on the material's surface. Therefore, sandwiching pyroelectric material between two metal layers enables charges to be collected at the pyroelectric-metal interfaces to generate electrical signals. Our work highlights a new combination of high transmittance (84.5%) and a lower number of layers alternating stack of Germanium/Aluminum oxide bandpass filter centered at 3250 nm with a customized thin lithium tantalate (LiTaO 3 , 60 µm) pyroelectric detector to demonstrate gas sensing with pyroelectricity at room temperature. In the presence of ethanol in the gas cell, the detection system shows a voltage signal drop attributed to the pyroelectric effect. This effect happens when light is absorbed by the ethanol molecules, thus, altering the detected temperature. As the ethanol volume concentration increases from 6% to 100%, the detected voltage difference increases from 0.1 V to 0.8 V. Thus, enabling the system to distinguish the various ethanol concentrations. The measurement system's sensitivity can detect and quantify the concentration of alcoholic beverages like beer(5%) and wine(13%). Notably, a complete detection is possible in less than 2 min, and the corresponding minimum detection level of 1700 ppm. [Display omitted] • 2-Dimensional thin lithium tantalate pyroelectric detector in selective gas sensing. • High transmittance (84.5%) and low number of layers mid infrared bandpass filter. • Ethanol vapor and alcoholic beverages detection and concentration quantification. • Proven lower limit detection of 1700 ppm in less than 2 min at room temperature. [ABSTRACT FROM AUTHOR]

The recent achievements in studying the self-assembled evolution of micro- and nanoscale domain structures in uniaxial single crystalline ferroelectrics lithium niobate and lithium tantalate have been reviewed. The results obtained by visualization of static domain patterns and kinetics of the domain structure by different methods from common optical microscopy to more sophisticated scanning probe microscopy, scanning electron microscopy and confocal Raman microscopy, have been discussed. The kinetic approach based on various nucleation processes similar to the first-order phase transition was used for explanation of the domain structure evolution scenarios. The main mechanisms of self-assembling for nonequilibrium switching conditions caused by screening ineffectiveness including correlated nucleation, domain growth anisotropy, and domain–domain interaction have been considered. The formation of variety of self-assembled domain patterns such as fractal-type, finger and web structures, broad domain boundaries, and dendrites have been revealed at each of all five stages of domain structure evolution during polarization reversal. The possible applications of self-assembling for micro- and nanodomain engineering were reviewed briefly. The review covers mostly the results published by our research group.

Defects production and evolution in H and He ions co-implanted LiTaO 3 under different implantation order (H + He and He + H) are investigated. Rutherford backscattering spectrometry (RBS), infrared (IR) spectroscopy and transmission electron microscopy (TEM) are used to study the lattice damage, composition and structure change in the buried damage region. Obvious differences of ions aggregation mechanism are found in H and He implanted LiTaO 3 . Blistering or splitting of LiTaO 3 is more easily achieved in the case where He is implanted first compared to the reverses case. Significant damage enhancement and micro-fractures are observed in samples with He preimplant. The dispersed damage in H-first sample is due to the destruction by He post-bombardment of H-clusters. This order effect indicates the strong aggregation and trapping ability of He ions and He bubbles. The effect of coimplantation parameters on the cleaving of LiTaO 3 is discussed. [ABSTRACT FROM AUTHOR]

Hydrogen incorporation into lithium niobate and lithium tantalate during crystal growth has attracted research interest for a long time, but the diffusion paths and defect sites within the materials are only partially understood. In the present study, the hydrogen defect is investigated by crystal orientation and light polarization resolved FT-IR spectroscopy. The OH − absorption band is splitting in two sub-bands, which are significantly affected by intrinsic defects. We attribute the line broadening of both band components to the antisite defect cluster, which is decorated by hydrogen. LiNbO 3 and LiTaO 3 although, isomorphic in crystal and defect structure, differ significantly in their antisite defect cluster concentration and, as we show, also in the occupation of hydrogen bonding sites in the structure. [ABSTRACT FROM AUTHOR]

Lithium niobate (LiNbO3 or LN) and lithium tantalate (LiTaO3 or LT) crystals, which have been widely applied in many fields such as electro-optics, birefringence, nonlinear optics, photorefraction, piezoelectricity and other areas, are reviewed. The studies of the properties and growth techniques are reviewed to give a brief idea of the growth of LN and LT crystals with high quality. The anti-site defects of these crystal materials have been accepted as one of the key factors constraining the improvement of their properties. This review shows the simulated calculation and structure of anti-site defects in LN/LT crystals and their effect on the physical properties and summarizes the recent progress in theoretical and technical processes, including the improved applications. We reviewed two main methods for the elimination of anti-site defects: doping of metal ions and growth of stoichiometric crystals. Finally, the prospects for future studies are outlined. [ABSTRACT FROM AUTHOR]

Imaging of ferroelectric domains using scanning electron microscopy is challenging as ferroelectrics are usually highly insulating. However, micro and nanodomain patterns can be directly visualized in secondary electrons using proper parameters. Low accelerating voltage or local charge compensation allows visualizing isolated domains with sizes above 100 nm without any sample preparation. Nanodomain patterns can be visualized with resolution about 3 nm after proper preparation of the sample surface: controlled chemical etching to obtain nanoscale surface relief and subsequent covering of the crystal surface by conductive film. Features of visualization of various nanodomain structures by scanning electron microscopy are considered. [ABSTRACT FROM PUBLISHER]

Thermal time constant ( τ ) is one of the most important parameters of pyroelectric detectors (PEDs). However, unlike other parameters such as voltage responsivity ( R ), noise equivalent power and specific detectivity ( D*), measurement of τ of lithium tantalate (LT) based PEDs was seldom reported in literatures. In this work, a convenient direct method for the measurement of τ was presented according to theoretical analysis and simulation result. Afterwards, this method was successfully applied to practical measurement of a homemade current mode terahertz (THz) LT based PED, of which τ was measured to be about 882 ms. To verify the measured result, τ was also calculated from the measured voltage-time curves according to its theoretical expression, which agrees well with the measured one. Compared with indirect measurement of τ through frequency response curves of PEDs, the direct method is simpler and more accurate. Furthermore, this method suggested an easy way for the measurement of pyroelectric coefficient of PEDs. [ABSTRACT FROM AUTHOR]

The feasibility of a LiTaO 3 pyroelectric crystal for pulsed neutron detection has been studied. The detector consists of a slice of electroded Z-cut LiTaO 3 pyroelectric crystal, and no additional neutron converter is required owing to the Li contained in the crystal. The slight temperature increase caused by neutron radiation will lead to the release of bound charges and will give rise to a pyroelectric signal. The response of it has been studied both theoretically and experimentally. Our preliminary experiment on the CFBR-II reactor suggests that the LiTaO 3 pyroelectric detector is promising for high intensity neutron – pulse measurement. [ABSTRACT FROM AUTHOR]

In the paper we review the self-organized formation of exotic dendrite-shape domain structures in ferroelectric single crystals. The main attention is paid to our recent detail experimental study of the dendrite domain growth during polarization reversal in stoichiometric lithium niobate LiNbO3at elevated temperature and in congruent lithium tantalate LiTaO3after pulse laser heating. Optical, confocal Raman, scanning electron, and piezoelectric force microscopy have been used for domain visualization at the surface and in the bulk. The key roles of isotropic domain growth at elevated temperature, correlated nucleation effect, and ineffective screening of the depolarization field have been revealed. [ABSTRACT FROM AUTHOR]

The electronic conductivity was measured in single crystals of lithium niobate and lithium tantalate family at elevated temperatures using direct electrometric method with original technique of compensation of pyroelectric current. Experimentally measured temperature dependences of the bulk electrical conductivity along the polar direction followed the Arrhenius law with activation energy ranging from 1.0 to 1.2 eV. It was shown that bulk intrinsic conductivity became the main mechanism of screening at the temperatures above 160°C. The conductivity anisotropy was studied in MgOLN single crystals. [ABSTRACT FROM AUTHOR]

The switching in the bulk only in lithium tantalate single crystals with modification of the surface layer by short-time low energy ion irradiation has been studied experimentally. It was shown by us earlier that in lithium niobate single crystals such irradiation led to spatially inhomogeneous increase of the bulk conductivity and allowed us to create by polarization reversal the stable domain structure with charged domain walls. In this paper, we compare the features of the domain structure evolution and growth of the charged domain walls in modified crystals of lithium tantalate and lithium niobate. [ABSTRACT FROM AUTHOR]

Formation of the micro- and nanodomain structures in congruent lithium tantalate single crystal under the action of pyroelectric field induced by pulse infrared laser irradiation at elevated temperatures was investigated. Three types of the self-organized domain structures were obtained: (1) the self-similar domain structure formed in crystal regions heated below Curie temperature, (2) the maze-type domain structure, and (3) irregular-shaped isolated domains formed in the regions heated above Curie temperature. The results of calculation of the time dependent spatial distribution of the temperature and pyroelectric field have been used for explanation of the peculiarities of domain structure formation. [ABSTRACT FROM AUTHOR]

The polarization reversal was studied in single crystals of lithium tantalate with intermediate deviation from stoichiometric composition (([Li]/([Li]+[Ta]) = 48.9%) with and without surface photoresist layer. The switching current was analyzed according to the stages of domain structure evolution revealed duringin situvisualization of domain kinetics. The characteristic times of the switching process were extracted by fitting of the experimental data using modified Kolmogorov-Avrami model. The formation of the self-assembled domain chains was observed during polarization reversal with photoresist dielectric layer on one polar surface. [ABSTRACT FROM AUTHOR]

As a typical multi-functional single crystal material, lithium tantalate (LiTaO 3 or LT) exhibits its excellent electro-optical, piezoelectric properties and has now been widely applied into many applications, such as electro-optical modulators, pyroelectric detectors, optical waveguide, piezoelectric transducers and SAW (surface acoustic wave) substrates. LT is known as a very important functional material, however the details of its machinability are not readily available yet. The content in this study is firstly focuses on the physical properties of LT like piezoelectric and pyroelectric effects and their influence on grinding performance. The obtained results are analyzed and discussed to understand its physical properties which have significant influences on their machinability in the grinding process. The crack initiation is possible to be dominated by internal stress which originated from self-polarization of the material itself. Hence, in order to suppress the physical effects induced by polarization during grinding of LT, control the temperature of coolant and increase the electrical conductivity of coolant are purposely tried in this study. The grinding results suggest that control of coolant temperature and use of electrolyte solution can effectively suppress the increasing rate of grinding torque and surface roughness, which in turn enhance the performance of LT wafer grinding. The LT wafers are eventually able to be thinned less than 100 μm. [ABSTRACT FROM AUTHOR]

In this letter we exhibit a series of results obtained using the technique of photothermal spectroscopy to determine the concentration of water in water–ethanol solutions. At low concentrations water is completely miscible with ethanol and particularly difficult to separate into parts in order to determine the complementary amount of each component, especially when considering measurements for such quantification in large scale. Ethanol has been promoted to a special class of product in the last decade due to its use as a renewable fuel for cars. However, it is of extreme importance to control the amount of water mixed in ethanol in order to avoid all sorts of erroneous possibilities regarding the indications for best performance of the engines. The results presented in this paper indicate the possibility of a new systematic setup to determine accurately the water content on water–ethanol solutions using photo-thermal techniques. [ABSTRACT FROM AUTHOR]

The bidomain structures produced by light external heating in z-cut lithium niobate and lithium tantalate single crystals are formed and studied. Interdomain regions about 200 and 40 μm wide in, respectively, LiNbO and LiTaO bidomain crystals are visualized and studied by optical microscopy and piezoresponse force microscopy. Extended chains and lines of domains in the form of thin layers with a width less than 10 μm in volume, which penetrate the interdomain region and spread over distances of up to 1 mm, are found. [ABSTRACT FROM AUTHOR]

Highlights • SLT crystals with thickness of 3.2 mm were prepared by VTE method. • The chemical composition in SLT crystals is about 49.99 mol%. • The forward and reverse poling fields are 159 V/mm and 145 V/mm, respectively. Abstract A stoichiometric lithium tantalate (SLT) crystal, 3.2 mm in the thickness and approximate 56 mm in the diameter, was prepared employing improved vapor transport equilibration (VTE) method. The chemical composition in SLT crystals is about 49.99 mol%. The compositional depth profile and uniformity along the radial direction were characterized. The composition deviation in the whole wafer is less than 0.02 mol%. The poling fields for ferroelectric domain reversal of SLT crystals were measured by applying ramped voltages using liquid electrodes. The forward and reverse poling fields are 159 V/mm and 145 V/mm, respectively, and their uniformity in the whole SLT crystal is promising. [ABSTRACT FROM AUTHOR]