White-beam Synchrotron Radiation Topography Research Articles

Growth and defects of DAST crystal in high concentration solution

The 4-N,N-dimethylamino-4-N-methyl stilbazolium tosylate (DAST) crystal with large size and nearly square shape was grown in high concentration solution by slope nucleation method coupled slow cooling (SNM-SC). Striations considered as planar defects were found on the (001) face along a-axis in the crystal by optical microscope. Some of the striations were continuous while some of them were discontinuous. In addition, the striations were found on (231) diffracting face and such lines did not occur on the (3-21) and (−221) planes. The surface distribution and morphological structure of the crystal were characterized by XRD and atomic force microscope (AFM). The presence of striations in the sample was also confirmed by white-beam synchrotron radiation topography (WBSRT). The mechanism of striations formation was also discussed.

Synchrotron Radiation Topography on Domain Structure Induced by DC Electric Field in PZNT Ferroelectric Crystals

The ferroelectric domain’s structure and its evolution processes induced by DC electric field in 0.92Pb（Zn1/3Nb2/3）O3-0.08PbTiO3（PZNT）crystal is observed using synchrotron radiation white-beam topography. Two organic plates with tinsels covering their surfaces are used as electrodes to employ DC electric field, and the characterizing sample is two PZNT crystal slices whose surface orientation is [111] and [001], respectively. This research results is considered to be useful for demonstrating the electric field induced phase transition in PZNT crystals.

Cross-twinning in a natural spinel from Sri Lanka

A modified cross-twinning growth mechanism is put forward to explain the anomalous morphology of a spinel multiple-twin from Sri Lanka, flattened crosswise the twin planes. Cross-twinning in spinel was found also in other specimens from Pegu (Myanmar), and the results were published in a previous paper. This particular type of twinning is derived from the combination of cyclic twinning with lamellar twinning, so that these samples may be thought of as partial fivelings (cubic cyclic {111} twins with five components sharing a common pseudo-fivefold axis). In the present paper, the sample from Sri Lanka has been suitably cut with the aim of focusing the study on the cross-twinning region. The transformation matrices that link the orientation states of each couple of twin components have been determined by means of White Beam Synchrotron Radiation Topography. They showed that the specimen is made up of four twin components (A, B, C and D), with three twin planes: $$(\bar{1}11)_{\rm A/B}, (1\bar{1}\bar{1})_{\rm B/C}$$ and $$(\bar{1}\bar{1}\bar{1})_{\rm AC/D}.$$ They also showed that the cross-twinned individuals (B and D) actually are not twinned to each other, and that a simple crystallographic relationship holds between them. X-ray diffraction topography by conventional source allowed to image the crossing-region and to determine that the cross-twinned individuals are in contact through a semi-coherent boundary, with twinning dislocations contributing to relieve the coherency strains. Electron probe microanalyses with wave dispersive spectroscopy showed that the chemical composition is almost homogeneous, at least within the spatial resolution limit of this technique. The similar growth features observed in the spinel sample from Sri Lanka and in those from Myanmar are interpreted as growth marks, indicators of a similar origin: in both cases they are found in impure dolomitic marbles. In particular, the specimen from Sri Lanka results from the interaction of thermal and metasomatic effects due to contact metamorphism. An unusual stepped morphology of the $$(1\bar{1}0)_{\rm C}$$ face close to the $$(\bar{1}\bar{1}\bar{1})_{\rm C/D}$$ twin boundary, possibly due to corrosion and re-growth processes acted preferentially at a re-entrant corner by metasomatic fluids, is interpreted as indicator of a metasomatic event that succeeded to the crystal growth, the latter occurred by thermal effect.

Czochralski growth of YAP crystal doped with high Tm concentration

The Czochralski growth of Tm:yttrium aluminate (YAP) crystal (10 at%) has been presented. The as-grown crystal has been investigated by X-ray diffraction (XRD) method using its powder sample, which showed that only YAP phase existed and there was no TmAlO 3 phase in the crystal. The X-ray rocking curve (XRC) of as-grown crystal was determined, the full-width at half-maximum (FWHM ) is 31.5″. The absorption and fluorescence spectra of Tm:YAP crystal with different Tm concentration were measured. Though the absorption intensity of 10 at% Tm:YAP crystal is much bigger, its fluorescence intensity is smaller. Some “hidden defects” like core and growth striations could not be observed with naked eyes and microscope, but they could only be determined by synchrotron radiation white-beam topography (SRWBT) technique.

White-beam synchrotron topographic study of antiparallel 180° domains in near-stoichiometric LiNbO 3 grown from Li 2O-rich melt

A near-stoichiometric LiNbO 3 (N-SLN) single crystal has been grown by a Czochralski method from a melt of 58.5 mol% Li 2O composition. The N-SLN single crystal has been studied by white-beam synchrotron radiation topography. Due to the different structure factors between positive and negative domains at the reflection wavelength near the absorption edge of Nb atom, antiparallel 180° domains in N-SLN have been observed by anomalous scattering. The domain boundary is visible by black–white contrast from positive and negative domain and the ratio of | F ( 0 0 0 6 ) | 2 to | F ( 0 0 0 6 ¯ ) | 2 is calculated.

Synchrotron white beam topography studies of SrLaGaO 4 crystals

Strontium lantanum gallate SrLaGaO 4 tetragonal single crystal was investigated by white beam synchrotron radiation topography. Projection and section topographs were taken in back reflection and transmission geometry. The central “core” crystal region was practically free of defects; only one extended “oval” defect with strong boundary contrast was observed. The strong white–black contrasts connected with elongated volume defects and cracks were observed in surrounding the “core” region.

Study of growth defects in benzophenone crystals

Synchrotron radiation white-beam topography was used to investigate the defects in benzophenone crystals grown from undercooled melt. The individual grown defects, such as growth striations, dislocations, inclusions and cavities, were observed in the topographs. The origin of the defects in benzophenone crystals was analyzed, and the results indicated that the purity of materials and the degree of undercooling were the main causes of the formation of defects in benzophenone crystals.

In situ synchrotron radiation topography study of the anomalous phase transition behavior in unpoled 0.92Pb (Zn 1/3Nb 2/3)O 3–0.08PbTiO 3 crystals

Through the unique white-beam synchrotron radiation topography (WBSRT) method with several Al foils covering the sample, we have investigated in situ phase transition behavior in unpoled relaxor ferroelectric 0.92Pb (Zn 1/3Nb 2/3)O 3–0.08PbTiO 3 (PZN–8%PT) crystals and found it was anomalous to that reported previously. According to the ferroelectric domain growth behavior on heating and cooling, it was demonstrated that the unpoled PZN–8%PT crystal undergone three phase transitions, i.e., the rhombohedral-orthorhombic (R–O) phase transition at 75 °C, the rhombohedral-monoclinic or orthorhombic–tetragonal (R–M/O–T) phase transition at 132 °C, and the monoclinic or tetragonal–cubic (M–C/T–C) phase transition at 262 °C. DSC analysis revealed that the R–O phase transition and the M–C/T–C transition was of the first-order, while the R–M/O–T one belonged to the second-order type.

In situ observation of ferroelectric domain configurations in unpoled 0.92Pb(Zn 1/3Nb 2/3)O 3–0.08PbTiO 3 crystals by synchrotron radiation topography

In situ observation of ferroelectric domain structures and phase transition in unpoled 0.92Pb(Zn 1/3Nb 2/3)O 3–0.08PbTiO 3 (PZN–8%PT) crystals has been successful performed by real time white-beam synchrotron radiation topography (WBSRT) with several aluminum foils for surrounding the sample. This novel topography method can be used to overcome the shortage of the common WBSRT for investigating lead-contained crystals. The complex and unique configurations and dynamic behaviors of ferroelectric domain walls in unpoled PZN–8%PT induced by temperature variation were revealed, which were believed to be meaningful for indicating the intrinsic nature of the phase transition and the origin of the strong piezoelectricity in relaxor ferroelectric materials.

Characterization of 0.92Pb(Zn 1/3Nb 2/3)O 3–0.08PbTiO 3 crystals grown from high-temperature solutions

Large 0.92Pb(Zn 1/3Nb 2/3)O 3–0.08PbTiO 3 (0.92PZN–0.08PT) single crystals were grown successfully by the high-temperature solutions method using PbO as flux. The crystal was determined by powder X-ray analysis to have rhombohedral structure. The surface profile and topography of the crystals were investigated by atomic force microscopy and synchrotron radiation white-beam topography, through which defects such as scratches and inclusions were observed. The optical spectra show that the crystals’ absorption edge is 360 nm. The results of ferroelectric hysteresis loops experiments indicated that the ferroelectric parameters including saturation polarization, remnant polarization, and coercive field increased with the highest applied voltages. According to the differential thermal analysis curve, the melting point of 0.92PZN–0.08PT crystals can be found at approximately 1187°C.

Czochralski growth and topographic study of tetragonal (La,Sr)(Al,Ta)O 3 single crystals

Large tetragonal phase (La,Sr)(Al,Ta)O 3 (LSAT) crystals used as substrates for growing functional thin-film materials were successfully grown by the Czochralski method using [0 0 1] LaAlO 3 rod as seed. The crystal phase was determined by the method of powder X-ray diffraction analysis and the transmission spectrum indicates that the absorption edge of the crystal is at 270 nm while no apparent absorption peaks were found. Through the technique of environmental scanning electron microscopy and synchrotron radiation white-beam topography, the surface topography and defects were characterized, and clear and stable images of twins, micro-cracks, inclusions, grain boundaries, dislocation etch pits, and growth striations in the as-grown LSAT crystals were obtained.

Growth defects in BiB 3O 6 crystals observed with white-beam synchrotron topography

The growth defects in BiB 3O 6 (BIBO) crystals have been investigated by white-beam synchrotron radiation topography for the first time. It is found that inclusions, dislocations and growth sector boundaries are the primary growth defects nearby the seed. The area away from the seed is nearly free of defects. Based on the experimental observations, the formation mechanism of brown region in BIBO crystals is discussed. Twins and growth sector boundarie exist in the brown region, which is the key reason resulting in brown presentation. The approaches to reduce and eliminate the defects are presented.

Image shifts resulting from the misorientation of two individuals in GdCa 4O(BO 3) 3 crystal

Large GdCa 4O(BO 3) 3 crystal has been grown by the Czochralski method. The quality of GdCa 4O(BO 3) 3 crystal was assessed by white-beam synchrotron radiation topography. It has been found that there is a sub-grain boundary in the GdCa 4O(BO 3) 3 crystal. The boundary divides the large GdCa 4O(BO 3) 3 crystal into two individuals. Due to the misorientation between the two individuals, the image shifts can be observed in the synchrotron topographs. Based on the misorientation determined by high resolution X-ray diffractometer, the image shifts were calculated for several reflections. The calculations are in agreement with the measurements from the topographs very well. In addition, the formation mechanism of sub-grain boundary is discussed.

Synchrotron radiation topographic characterization of L-arginine phosphate monohydrate crystals

The growth defects in solution grown L-arginine phosphate monohydrate (LAP) organic crystals were investigated by white-beam synchrotron radiation topography. The crystals were cut into slices in different directions. The transmission topographies showed the dislocations, growth striations, growth sector boundaries and inclusions in both (100) slice and (001) slice with different reflection. We also presented the contrast of microbe, which is a severe problem in LAP crystal growth. The topography with 015 reflection showed the dislocations originated from the surface of the seed and following the (001) and (100) direction, and the Burgers vectors of those dislocations were determined. The dynamic images of growth sector boundaries were also showed clearly.

Dislocations in dendritic web silicon

Due to its peculiar laminated structure, dendritic web silicon presents one of the most interesting configurations of dislocations in Si crystals. On the way to growing dislocation-free Si webs, X-ray diffraction topography techniques were used to visualize the dislocations in the material. The results and the analysis of dislocation reactions reported here provide information on the mechanisms involved in the formation of dislocation networks in the material. Also, the applicability of synchrotron radiation white-beam topography for a rapid characterization of dislocations is investigated and discussed.

Measurement of elastic shear strain by white-beam SR topography

An external tensile stress applied to an elastically anisotropic cubic material along a direction different to that of the cubic axes can cause a shear deformation. In bicrystals the shear strain can result in a mutual tilt of some planes at the grain boundary. Taking advantage of the high sensitivity of the white-beam synchrotron radiation topography to the tilt of diffracting planes, the small elastic shear strain was measured using suitable bicrystals. source code)

Growth defects in flux grown RbTiOAsO 4 crystals observed with white-beam synchrotron radiation topography

The growth defects in flux grown RbTiOAsO 4 crystal have been investigated by white-beam synchrotron radiation topography. It is found that growth sector boundaries are the primary growth defects and they show strong X-ray kinematical contrast in the topograph. All the dislocations are growth induced and appear only in the near capping region. The area away from the capping region is nearly dislocation free. Growth bands show weak contrast in the X-ray topograph, which implies that the impurity contents are relatively low in various growth sectors and each growth sector is uniform in composition.

The application of synchrotron radiation techniques to the study of domain structures and their dynamics in ferroic crystals

The recent research work on domain structures and their dynamics in ferroelastic and ferroelectric crystals by white-beam synchrotron radiation topography is summarized. The real-time imaging, fine-beam Laue diffraction, and anomalous-scattering topography were carried out to the study of the domain structures and phase transition in the ferroelastic NdP5O14 and LaP5O14, and ferroelectric KTa1-xNbxO3, (Ba0.25Sr0.75)0.9(K0.5Na0.5)0.2Nb2O6, and KTiOPO4 crystals. Some preliminary results are presented and discussed.

Growth Twins in YbxY1−xAl3(BO3)4 and NdxGd1−xAl(BO3)4 Crystals Observed by White-Beam Synchrotron Radiation Topography

ABSTRACTGrowth twins in Ybx Y1−xAl3(BO3)4 (YbYAB) and NdxGd1−xAl3(BO3)4 (NGAB) crystals were observed by white-beam synchrotron radiation topography combined with chemical etch. It was found that growth twins in YbYAB crystals are of inversion types in which two twinned pairs have the central inversion relationship. This kind of twinning was visible in x-ray topography not by ‘domain contrast’ but by ‘boundary contrast’ stemming from the kinematical x-ray diffraction at the boundary. Growth twins in NGAB crystals are of 1800 rotation types in which the twofold symmetric operation axis is parallel to the [0001] axis. This kind of twinning often shows black-and-white contrast in x-ray topography which originates from the different structure factors between twinned pairs. In addition. the formation mechanisms of growth twins are discussed.

Growth Twinning in Self-Frequency-Doubling Laser Crystal NdxGd1—xAl3(BO3)4 Observed with White-Beam Synchrotron Radiation Topography

The growth twinning in self-frequency-doubling laser crystal NdxGd1-xAl3(BO3)(4) (NGAB) has been observed with white-beam synchrotron radiation topography (WBSRT). It is shown that the growth twinning in flux-grown NGAB crystal is the 180 degrees rotation twin in which the twofold symmetric operation axis is parallel to the [0001] direction and this kind of twinning often shows the black-and-white contrast in X-ray topography. It is believed that the growth twinning in NGAB was induced by growth bands formed during crystal growth.