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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Revisit the stress-orienting effect of θ' in Al-Cu single crystal during stress aging

Highlights: • The microstructures observed along two different <001>{sub Al} zone axes were determined. • Three-dimension precipitation distribution of θ'-precipitates was established. • The different rules of the stress-orienting effect on θ'-phase were proposed. • Two opposite views of the stress-orienting effect on θ' are compared in detail. • Increasing in number density of θ' is the other sign of the stress-orienting effect. - Abstract: Three-dimension precipitation distribution of θ'-precipitates was established to revisit the stress-orienting effect of θ'-phase in Al-Cu single crystal during stress aging, via determining the microstructure observed along two different <001>{sub Al} zone axes. The results show that the θ'-precipitates prefer to precipitate on the habit planes parallel to the loading orientation, rather than the habit planes perpendicular to the loading orientation proposed in current views. Two opposite models of the stress-orienting effect on θ'-phase are compared and discussed in detail. They show the same aligned θ'-precipitate structure while observed perpendicular to the loading direction (i.e. [100]{sub Al} or [010]{sub Al}). The crucial difference actually lies in the microstructure observed along the loading orientation (i.e. [001]{sub Al}), which shows an increasing tendency in the number density of θ'-precipitates with increasing applied stress. This result further proves that the θ'-precipitates prefer to precipitate on the habit planes parallel to the loading orientation. In addition to the aligned θ'-precipitate structure, the fact that the number density of θ'-precipitates is increasing can be also treated as the other sign of the stress-orienting effect.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Characterization of dislocation microstructures in cyclically deformed [001] copper single crystals using high voltage scanning transmission electron microscopy

Highlights: • High voltage scanning transmission electron microscopy is adopted. • Dislocation structure strongly depends on given plastic strain amplitude. • Evolution of dislocation structure from vein-like to labyrinth is revealed. - Abstract: Low-cycle fatigue tests of copper single crystals with the [001] stress axis were performed at room temperature under constant plastic shear strain amplitudes between γ{sub pl} = 3.5 × 10{sup − 4} and 1.0 × 10{sup − 2}. Characteristic dislocation structures, which are highly dependent on a given plastic strain amplitude, were observed by high voltage scanning transmission electron microscopy. A vein-like dislocation structure, having a parallelepiped shape with two longitudinal (100) and (001) sides, was periodically formed along the [010] direction at around γ{sub pl} = 1.0 × 10{sup − 3}. Labyrinth structure with the (100) and (001) dislocation walls was then gradually developed with increasing plastic strain amplitude.

36 MATERIALS SCIENCE↗
DOE OSTI2018

EBSD characterization of boundary types after discontinuous precipitation in a grit-blasted nickel-based superalloy

Highlights: • During recrystallization, high-angle grain boundaries increased dramatically. • The reaction fronts are high-angle GBs, but are not always correspond to CSL type. • Σ3 twin boundaries have been confirmed to be positive on reducing residual stress. • No advancing reaction front corresponds to Σ3 twin boundary type. - Abstract: In the present work, direct and detailed insights with respect to the statistical information on boundary type of discontinuous precipitates and their advancing reaction fronts in a Re-containing single crystal superalloy DD6 have been obtained by EBSD. With the annealing time prolonging, the reaction fronts proceeded into the original matrix for gradual release of grit-blast induced stress. The average recrystallized grain diameter and the average depth of recrystallization were respective 0.83 μm and 3.98 μm for the specimen annealed at 1050 °C for 10 min, which, after 16 h, had grown to the average values of 3.22 μm and 31.17 μm. The reaction fronts of discontinuous precipitation have been confirmed to be high-angle grain boundaries, but do not always correspond to CSL type. Besides the role of strain energy dissipation for recrystallization, the formation of twin structure has no direct relationship with the proceeding of reaction fronts. The information of boundary type of discontinuous precipitation and its advancing reaction fronts would provide new insight into the cellular recrystallization behavior.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Negative influence of rafted γ′ phases on 750 °C/750 MPa creep in a Ni-based single crystal superalloy with 4% Re addition

Highlights: • The negative influence of the rafted γ′ phases on creep was investigated. • The rafted sample exhibited a lower creep rate a shorter rupture life. • Fine γ′ phases impeded first the dislocation movement in γ matrix. • Existed superdislocations and the stress release decreased the creep resistance. • Rafted γ′ phases were more easily cut by superdislocations and stacking faults. - Abstract: Specimens with two different γ′ phase microstructures, named as-heat treated sample with cuboidal γ′ phases and pre-rafted sample with N-type rafted γ′ phases, were compared to investigate the negative influence of the rafted γ′ phases on the creep property in a Ni-based single crystal superalloy with 4% Re addition at 750 °C and 750 MPa condition. The results indicated that the sample with cuboidal γ′ phases exhibited a lower creep rate and a longer rupture life compared to that with rafted γ′ phases. Transmission electron microscope examinations showed that lots of fine γ′ phases impeded first the dislocation movement in the channel of γ matrix in the initial primary creep stage before the cuboidal γ′ phases were cut by stacking faults in as-heat treated sample. However, in pre-rafted sample, some existed superdislocations located in rafted γ′ phases and the mismatch stress release at γ/rafted γ′ interface resulting from pre-rafted treatment not only decreased the creep resistance of rafted γ′ phases, but also weakened the γ/rafted γ′ interface pinning effect for dislocation movement. Therefore, the rafted γ′ phases were easily cut by superdislocations and stacking faults resulting in a higher creep rate and a shorter creep life.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Characterization of niobium-doped titania epitaxial films deposited by metalorganic chemical vapor deposition

Highlights: • The undoped and Nb-doped TiO{sub 2} films were deposited on SrTiO{sub 3} (100) substrates. • The epitaxial growth relationship between TiO{sub 2} film and the substrate was confirmed. • The microstructures of the films were explored. • The electrical and optical properties of the films were revealed. - Abstract: Titania (TiO{sub 2}) films with different niobium (Nb) doping concentrations were deposited on SrTiO{sub 3} (STO) (100) substrates by metalorganic chemical vapor deposition (MOCVD). The crystal structures, surface morphologies, electrical and optical properties of the Nb-doped TiO{sub 2} (TiO{sub 2}:Nb) films varying with Nb content were investigated. The single crystal TiO{sub 2} films with anatase structure were obtained at low Nb doping levels. The highest Hall mobility of the prepared films reached as high as 16.50 cm{sup 2} V{sup −1} s{sup −1}. The lowest resistivity of 5.75 × 10{sup −2} Ω cm with a Hall mobility of 7.40 cm{sup 2} V{sup −1} s{sup −1} and a carrier concentration of 1.47 × 10{sup 19} cm{sup −3} were obtained from the 1.20% Nb-doped TiO{sub 2} film. This resistivity was about 6 orders of magnitude lower than the undoped TiO{sub 2} film. Moreover, all the deposited films exhibited high average transmittances of over 88% in the visible wavelength range.

36 MATERIALS SCIENCE↗
DOE OSTI2018

A study on spherical particles in Al65Cu20Fe15 alloy prepared by arc melting

Highlights: • Spherical particles and facets were found. • Spherical particles consist of quasicrystalline grains embedded in single crystal matrix. • Facets were found on the surface of spherical particles, which can be classified to three types. • A model for the formation of spherical particles is suggested. • Reasons for the formation of facets are discussed. - Abstract: Al-Cu-Fe alloys are important due to reports that stable icosahedral quasicrystalline phase with composition in the vicinity of Al{sub 65}Cu{sub 20}Fe{sub 15} can be prepared. However, it has been widely reported that the as-prepared alloy, very often by arc-melting, is porous, consisting of particles with different morphologies. Among these, one type of particles of a spherical shape is considered as pure cubic β phase in previous reports. In this research, this spherical particle was studied using a Scanning Electron Microscope, Energy Dispersive X-ray Spectroscopy, Transmission Electron Microscope, and Electron Diffraction. It was found that the particles are not single phase, consisting of icosahedral quasicrystalline grains embedded inside single crystal matrix of τ phase. Additionally, there are places where the τ phase appears to have out-most layer enriched in Cu. The surface of the particles is faceted and the facets can be classified to three types according to their detailed structures. A close examination and analysis led to the conclusion that these three types are parallel to the atomic planes of {1 1 0}, {1 1 1}, and {1 0 0}, respectively. A model for the spherical particle formation is suggested and the reasons for the formation of facets are discussed. This report is valuable in clarifying some discrepancies in previous reports, and in understanding the phase development in an Al-Cu-Fe alloy system.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Influence of temperature on the lattice misfit and elastic moduli of a Ni based single crystal superalloy with high volume fraction of γ′ phase

Highlights: • The variation of the lattice misfit with temperature in a Ni based single-crystal superalloy with high volume fraction of γ' phase was determined by high-temperature X-ray diffraction (HT-XRD) technique at temperatures between 25 °C and 1200 °C. • When the temperature was higher than 1100 °C, the γ' phase obviously dissolved, leading to a lower content of Mo and Re in the γ phase, and then resulted in a smaller absolute value of the lattice misfit. • The contribution of dissolution of γ′ phase to the reduction of the misfit increased with rising temperature and reached 29.5% at 1200 °C. • When the temperature exceeded 1100 °C, the difference of elastic moduli of γ and γ′ phases increased with rising temperature was attributed to the elastic modulus of γ phase decreased significantly. - Abstract: The variation of the lattice parameter with temperature in a Ni based single-crystal superalloy with high volume fraction of γ′ phase IC32 was determined by high-temperature X-ray diffraction (HT-XRD) technique at temperatures between 25 °C and 1200 °C. The effects of the temperature, especially the ultra-high temperature (beyond 1100 °C), on lattice misfit, elastic moduli, γ′ volume fraction and composition of γ, γ′ phases were investigated in this study. The results show that the absolute value of lattice misfit first increased and then decreased with increasing temperature and reached the maximum of 0.53% at 1100 °C. When the temperature was higher than 1100 °C, the γ′ precipitate obviously dissolved, leading to a lower content of Mo and Re in the γ phase, and then resulted in a smaller absolute value of lattice misfit. The contribution of dissolution of γ′ phase to the reduction of the misfit increased with rising temperature and reached 29.5% at 1200 °C. Moreover, when the temperature was above 1100 °C, the elastic moduli of the γ phase and alloy decreased significantly, while this phenomenon was not observed in the γ′ phase.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Elements distribution and deformation features of a 4.5% Re nickel-based single crystal superalloy during creep at high temperature

Highlights: • Atom probe is used to investigate the element concentration changes in γ and γ' phase during creep. • Mo, W and Re diffuse from γ' to γ phase and enrich in γ/γ' interface during high temperature creep. • Super-dislocations in γ' phase may cross-slip from {111} to {100} plane due to the elements diffusions. • Dislocations shearing into γ' phase may decompose into K-W locks plus APB due to the refractory elements enrichment. - Abstract: By means of creep property measurement, microstructure observation and atom probe tomography, the elements distribution and deformation features of a 4.5% Re nickel-based single crystal superalloy during creep are investigated. Results show that after fully heat treated, the elements Al and Ta are mainly distributed in γ′ phase of alloy. After the alloy is crept up to fracture at 1100 °C/137 MPa, the change of the elements distributing in γ and γ′ phases occurs, wherein, the concentration decrement of the elements Al and Cr in γ′ and γ phases is attributed to their oxidation which may consume the ones. Moreover, some of the atoms Re, W and Mo dissolving in γ′ phase are repelled into γ matrix to reduce its internal energy. And the peak concentration of the atoms Re and W appears in the γ phase near the transition region, the atoms Re, W in the peak region cause the lattice distortion to increase the resistance of dislocations motion, which may improve the creep resistance of alloy. In the later stage of creep, dislocations shearing into the rafted γ′ phase may cross-slip from {111} to {100} plane to form the configuration of K-W locks, which may restrain the slipping of dislocations to improve the creep resistance of alloy. Wherein, the atom Re with lower diffusion coefficient may delay the dislocations in K-W locks for slipping and cross-slipping, which is thought to be the main reason of the K-W locks keeping in 4.5%Re alloy during creep at 1100 °C.

36 MATERIALS SCIENCE↗
DOE OSTI2018

A compositional gradient Ce1−xZrxO2 buffer architecture for producing high-performance YBCO film

Highlights: • The compositional gradient CZO buffer architecture can help improve the biaxial texture of YBCO film. • The high density stacking faults are directly observed via a spherical aberration corrected transmission electron microscope. • The enhanced flux pinning force and current-carrying capacity of YBCO films are achieved as a result of lattice strains. - Abstract: In this work, YBCO films were epitaxially grown on Ce{sub 1−x}Zr{sub x}O{sub 2} (CZO) buffered yttria stabilized zirconia (YSZ) single crystal substrates through a fluorine-free sol-gel process. The influence of two different CZO buffer architectures on the microstructure and superconducting properties of YBCO films was investigated. According to XRD results in combination with (S)TEM analysis, it was confirmed that YBCO film grown on the gradient CZO buffer layer (CZO-G) exhibits better in-plane and out-of-plane texture than YBCO film deposited on the uniform CZO buffer layer (CZO-20). And besides, the superconducting performances especially the current-carrying capacity under magnetic field of the former was much higher than that of the latter, which means that the enhanced flux pinning force will be presented in YBCO film on CZO-G buffer layer. The maximum pinning force of the YBCO film grown on CZO-G buffer architecture is up to 17.67 GN/m{sup 3} @ 65 K. HR-STEM analysis shows that the stacking faults within YBCO matrix gave rise to the considerable nanoscale lattice-strains which may suppress the formation of Copper pairs and produce nanoscale non-superconducting regions served as pinning centers to significantly improve the flux pinning performance of YBCO film. Given the above, it has been implied that high-performance YBCO coated conductor can be developed by using a compositional gradient Ce{sub 1−x}Zr{sub x}O{sub 2} films as buffer architecture.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Dislocation arrangements within slip bands during fatigue cracking

Highlights: • Dislocation cells form near early slip bands fatigue cracks in wavy-slip materials. • Lattice rotates severely and grain boundaries form between neighboring cells. • The walls of dislocation cells are preferential sites for fatigue cracking. - Abstract: Microstructures and dislocations associated with the slip band (SB) fatigue cracks were investigated in Cu single crystal and bicrystal. It is found that there are high strain localizations with abundant dislocation cells around the cracked SBs. Due to the high local strain and slip irreversibility, the lattice rotates severely leading to large misorientation and hence low- or high- angle grain boundaries could form between the neighboring cells. Moreover, the dislocation walls can serve as preferential sites for nucleation and propagation of fatigue cracks with high density of dislocations, vacancies and high strain incompatibility.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Sparse modeling of space- and time-varying diffraction response of a progressively loaded aluminum alloy

Highlights: • Plasticity induces crystal orientation and lattice spacing heterogeneity. • High energy x-ray diffraction spot broadening typically accompanies plasticity. • Method quantifies spot broadening in difficult, mixed microstructure data. • Algorithm finds sparse combination of entries from dictionary of peak functions. • Approach showed asymmetric plastic response in preprocessed AA7075 T651 sample. - Abstract: High energy X-ray diffraction data collected in situ during loading experiments permits probing of the crystal structure of a plastically deforming material sample. An elastoplastic deformation is associated with heterogeneity in both crystal orientation and lattice spacing—each manifesting as azimuthal broadening and radial broadening of diffraction peaks respectively. Quantifying the spreading effect is challenging, especially in cases where the sample has a granularity between that of a single crystal and fine grain or powder material. The approach developed in this paper begins by modeling the intensity signal in the vicinity of a Debye-Scherrer ring as a sparse, nonnegative superposition of Gaussian basis functions drawn from an over-complete dictionary. Processing automatically selects from the dictionary basis functions whose widths and amplitudes are representative of the data. The chosen basis functions are used to compute scalar measures of radial and azimuthal broadening for the set of diffraction peaks composing a Debye-Scherrer ring. To demonstrate the utility of the approach, we show that analysis of diffraction peak shape information from an aluminum alloy 7075 T651 (AA7075 T651) sample provides insight into the origin of material state that would have otherwise have been difficult if not impossible to extract using conventional methods. Furthermore, the extracted information revealed a deformation response linked to the processing history of the sample.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Free surface effects on the recrystallization of compressed, stable, Al-Mn single crystals

Highlights: • The free surface provokes high frequency nucleation. • The free surface and surface ‘quality’ do not modify the orientations of the recrystallized grains. • The misorientation relations across recrystallization front are similar for all sections of both orientations. The free surface effect on the grain crystallography and morphology during recrystallization has been studied in stable Goss {110}001 and brass {110}112 - oriented single crystals of Al-1%wt.Mn alloy. The samples were plane strain compressed up to a strain of about 0.5 to develop a homogeneous structure comprising two sets of symmetrical microbands and then lightly annealed. The variation of recrystallization after annealing was then analysed by optical microscopy and SEM/EBSD on different cross-sections. The results are discussed in terms of the misorientation angle and axis distributions. The free surface provokes high frequency nucleation leading to a small grain size compared to internal sections of the bulk sample. However, the free surface and surface ‘quality’ do not modify the orientations of the recrystallized grains, i.e. similar groups of recrystallized grain orientations were observed for all sections. This leads to a strong misorientation relation between deformed/recovered area orientations and the limited number of groups of recrystallized grain orientations, basically the same as those observed during bulk recrystallization of similar crystals.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Crystal rotation and microstructures in an aluminum single-slip system under tensile loading

Highlights: • The crystal rotation angle with the progression of ductile damage was larger in the vertical plane than that in the horizontal plane. In the measurement along 110, the relative rotation angle was the maximum at the intersection of 111 and 110. • The integrated intensity and the FWHM decreased near the notch (from 0 to 0.3 mm) as well as at the intersection of 110 and 111 in the measurement along 110. • The dislocation cell size and the dislocation density decreased at the intersection of 111 and 110 in the measurement of 110 for ε = 5%. This behavior was attributed to the strain energy being released by the rotation of the dislocation cell. We experimentally investigated the rotation angle of the (220) plane in an aluminum single-slip system in which the angles of 110 and 111 in the single crystal were 45° relative to the tensile loading direction. Crystal rotation was investigated at several spots (50 × 50 μm) along 110 and 111 using synchrotron radiation white X-rays at the BL28B2 beamline of super photon ring-8. In measurements along the 110 axis, at an applied strain of ε = 5%, the relative crystal rotation of (220) in the vertical plane increased from 0.850° to 5.438° in the range of 0.9 to 1.4 mm. We observed the microstructure using a transmission electron microscope and verified the size of the dislocation cells or subgrains at each spot along 110. The fundamental local crystallography revealed in this work should be helpful in establishing a method for evaluating ductile damage in materials.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Scintillation, dosimeter and optical properties of MgF2 transparent ceramics doped with Gd3+

Highlights: • We have developed MgF{sub 2}:Gd{sup 3+} transparent ceramics by SPS. • The samples showed luminescence due to the 4f-4f transitions of Gd{sup 3+}. • The 1% Gd-doped sample has high TSL sensitivity equivalent to commercial personal dosimeters. - Abstract: In this study, we have developed MgF{sub 2}:Gd transparent ceramics by spark plasma sintering (SPS) and evaluated the scintillation, dosimeter and optical properties. All the sample were successfully synthesized in a transparent form with relative densities over 99% to that of the single crystal. The samples were confirmed to show scintillation, thermally-stimulated luminescence (TSL) and optically-stimulated luminescence (OSL). The origin of these emissions was due to the 4f-4f transitions of Gd{sup 3+} appearing as a single peak at 310 nm. In particular, the TSL was very sensitive to X-rays, and especially the 1% Gd-doped sample showed a sensitivity as low as 0.1 mGy. The TSL response increases monotonically with the irradiation dose, and the dynamic range was confirmed to be over 0.1–1000 mGy, which was equivalent sensitivity to that of commercial personal dosimeters.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2018

Fabrication and characterization of electrospun single-crystal lead manganese borate nanofibers

Highlights: • Single crystal PbMnBO4 nanofibers were successfully fabricated by electrospinning process. • The PbMnBO4 nanofibers synthesized for the first time and unprecedented in the literature. • Characterization of PbMnBO{sub 4} nanofibers in mineralogical, optical and thermal properties was revealed. • The nanofibers exhibit single crystalline features with an average size between 120 and 250 nm. • These nanofibers can be used in optic or photonic fields as a flexible sensor due to its nonlinear and ferromagnetic properties. - Abstract: Anhydrous borate compounds are important materials in optical applications as nonlinear optical materials (NLO), due to the presence of structural B{sub x}O{sub y} subunits. Herein, lead manganese borate (PbMnBO{sub 4}) nanofibers have been firstly fabricated via a facile approach using a simple and inexpensive electrospinning technique. All of the synthesized samples were analyzed with X-Ray Diffractometer (XRD), Transmission Electron Microscope (TEM), Scanning Electron Microscope (SEM), Fourier Transform Infrared (FTIR), and Ultraviolet-visible Spectroscopy (UV–vis) method. In addition, they were thermally analyzed with Thermal Gravimetric and Differential Thermal Analyzer and TG-DTA diagrams were discussed in detail. All of the characterization results showed that the obtained PbMnBO{sub 4} nanostructures have nanofiber structures and good crystalline features. PbMnBO{sub 4} nanofiber synthesized for the first time and unprecedented in the literature is promising absorber materials for nonlinear optic applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Magnetic studies on Sm0.55Sr0.45Mn0.4Fe0.6O3 single crystals grown by optical floating zone technique

Highlights: • Single crystals of Sm0.55Sr0.45Mn0.4Fe0.6O3 were grown by optical floating zone technique. • Replacement of Mn by iron has suppressed the double exchange interactions and ferromagnetism. • Crystal exhibited spin glass behavior below 35 K due to the competition between the Mn{sup 3+}-O-Mn{sup 4+} double exchange and the Mn{sup 3+}-O-Fe{sup 3+} super exchange interactions. - Abstract: Single crystals of high concentration iron substituted Sm{sub 0.55}Sr{sub 0.45}Mn{sub 0.4}Fe{sub 0.6}O{sub 3} were grown by optical floating zone technique in oxygen atmosphere. Analysis of powder X-ray diffraction and Laue patterns revealed single-phase formation and crystal quality respectively. Replacement of Mn by iron has reduced the ratio of trivalent to tetravalent Mn ions thus suppressing the double exchange interactions and ferromagnetism. The grown crystal exhibits spin glass behavior below 35 K due to the competition between the Mn{sup 3+}-O-Mn{sup 4+} double exchange and the Mn{sup 3+}-O-Fe{sup 3+} super exchange interactions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Anisotropic ionic transportation performances of (100) and (112) planes in MAPbI3 single crystal

Highlights: • Anisotropic ion transportations of MAPbI{sub 3} are studied. • Photon excited ion transportation is investigated. • Linear increase trends with incident light power of ion transportation are observed. • Enhanced electron and ion transportations have been observed on (112) plane of MAPbI{sub 3}. • (112) plane of MAPbI{sub 3} shows more active transportation properties than (100). - Abstract: Organic–Inorganic hybrid perovskites attract intensive attentions due to significant optoelectronic performances. However, abnormal phenomena such as photocurrent hysteresis and slow photoconductivity response caused by ion migration made ionic transportation properties to be a hot topic in this area. Thinking of serious influences such as efficiency decay of excited carrier separation and poor reliability are caused by ion migration, systematical research on this topic is still highly demanded. Here, anisotropic ionic transportation performances of (100) and (112) planes in MAPbI{sub 3} single crystal have been investigated with various photon excitation conditions. Enhanced ionic conductance had been extracted on (112) plane both with and without illuminations. Comparing to exponential saturation revealed by the electrons, the ionic conductance exhibits a linear increase trends with incident light power in MAPbI{sub 3}.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Stable dielectric, elastic, and piezoelectric properties of Yb3+:CNGS crystals at high temperature

Highlights: • Single crystals Yb:CNGS with high quality have been successfully grown using the Czochralski method. • The dielectric, elastic and piezoelectric coefficients are measured and calculated according to the impedance method. • Piezoelectricity and dielectric properties at room temperature and elevated temperature are investigated for the first time. • The doped crystals show good temperature stability at elevated temperature condition. - Abstract: In this study, Yb{sup 3+}:Ca{sub 3}NbGa{sub 3}Si{sub 2}O{sub 14} (Yb{sup 3+}:CNGS) single crystals with different doping concentrations (2 and 5 at%) were grown using the Czochralski method. The dielectric, elastic, and piezoelectric coefficients at room temperature and elevated temperature were measured and calculated according to the impedance method for the first time. Crystals show excellent piezoelectricity and exhibit favorable temperature stability from room temperature to 800 °C. The transmittance spectrum of the Yb{sup 3+}:CNGS crystals is also recorded, and the results prove the high optical quality of these crystals.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗