Solid Solution Single Crystals Research Articles

Heat Capacity and Features of the Phonon Spectrum of Single Crystals of Solid Solutions of Yttrium-Lutetium Alumogranates

Heat Capacity and Features of the Phonon Spectrum of Single Crystals of Solid Solutions of Yttrium-Lutetium Alumogranates

Effect of Mo addition on the microstructure and superelastic properties of Fe-Mn-Al-Ni alloy

This study systematically investigated the effect of Mo addition on the microstructure and superelasticity of Fe-Mn-Al-Ni alloy. The findings indicate that the addition of Mo element efficaciously suppressed the formation of γ phase after air cooling. Single crystal samples were prepared through cyclic heat treatment. The size of the precipitates in the solid-solution single crystal was found to be ∼ 12.90 nm. In contrast, the mean precipitates size in the aging single crystal was ∼ 18.07 nm. An excellent superelasticity with an average recoverable strain of ∼ 8 % at an applied strain of ∼ 9.5 % can be obtained in both the solid solution and aging single crystals with a near [-412] orientation. The Mo addition widens the size range of precipitates with good superelasticity up to ∼ 18 nm. Additionally, there is a significant difference in the superelastic performance of single crystals with different orientations. Superelastic strain values for orientated single crystals near [-412], [1-20] and [‐14‐3] were 5.5 %, 4.8 % and 4.4 %, respectively.

Heat Capacity and Features of the Phonon Spectrum of Single Crystals of Solid Solutions of Yttrium–Lutetium Aluminum Garnets

The temperature dependences of the heat capacity were measured and the general patterns of the formation of the phonon spectrum of single crystals of solid solutions of yttrium-lutetium aluminum garnets Y3 – xLuxAl5O12 at 0 ≤ x ≤ 3 were investigated in the temperature range from 1.9 to 220 K. According to the data obtained at temperatures below 10 K, the Debye temperatures were calculated. The features of the phonon spectrum in the intermediate temperature range are interpreted as a superposition of optical modes for yttrium and lutetium garnets. It is shown that the low heat capacity values due to the contribution of acoustic phonons for Y2.25Lu0.75Al5O12 correlate with anomalies in the concentration dependences of the phonon transport, the absorption of acoustic waves, and the shape of the aluminum NMR line.

Visualization of the Magnetic Domain Structure in FeBO3 and Fe0.94Ga0.06BO3 Single Crystals by Synchrotron X-Ray Topography

The method and experimental cell for the X-ray diffraction diagnostic of crystalline materials exposed to magnetic fields have been described. It has been shown that the application of even weak magnetic fields (about several Oersteds) allows one to significantly reduce the diffraction contrast on X-ray topograms of FeBO3 and Fe0.94Ga0.06BO3 single crystals, which is due to a nonuniform distribution of magnetostriction strains, and thereby to improve the degree of their structural perfection. The magnetic domain structure of Fe1 –xGaxBO3 solid solution single crystals has been visualized. It has been found that small concentrations of diamagnetic Ga ions do not significantly change the configuration of domain walls in FeBO3-based crystals.

Solid solutions of lithium niobate and lithium tantalate: crystal growth and the ferroelectric transition

Specific heat capacity measurements by differential scanning calorimetry (DSC) of single crystals of solid solutions of LiNbO3 and LiTaO3 are reported and compared with corresponding ab initio calculations, with the aim to investigate the variation of the ferroelectric Curie temperature as a function of composition. For this purpose, single crystals of these solid solutions were grown with Czochralski pulling along the c-axis. Elemental composition of Nb and Ta was investigated using XRF analysis, and small samples with homogeneous and well known composition were used for the DSC measurements. We observed that the ferroelectric Curie temperature decreases linearly with increasing Ta concentration in the LiNb Ta O3 solid solution crystals. Furthermore, the ferroelectric transition width of a mixed crystal appears to be smaller, as compared to pure LiTaO3.

Effect of cobalt content on point defects and local structure in activated Ca3(VO4)2 single-crystal solid solutions

Doping-induced structural changes of Co-activated calcium orthovanadate Ca3(VO4)2 (CVO) single crystals and specific local behavior of cobalt ions depending on the dopant content are presented in this paper. CVO is activated with over-stoichiometric Co3O4 of different concentration (CVO:xCo; x ​= ​0.1, 0.5, 1.0, 1.5, 2.0 ​wt %) during the Czochralski growth. Single-crystal synchrotron X-ray diffraction study shows gradual increase in the number of Ca crystallographic sites occupied by cobalt ions with increasing dopant concentration: from Ca3 site for CVO:0.1Co to additionally Ca2 and Ca4 sites for CVO:0.5–1.5Co, and also to Ca1 site for CVO:2.0Co. Vacancies in the tetrahedral vanadium V2 site are detected for all samples, and those in the tetrahedral V1 site are additionally found for CVO:2.0Co. Disordering of O1, O4, O7 oxygen sites is observed in all structures. Combined results of X-ray diffraction analysis and X-ray absorption spectroscopy showed that the formal charge of Co ions is mixed between 2+ and 3+ with the prevalence of 2+. A trend towards a decrease in formal charge with an increase in Co concentration is observed. The coordination number of Co(2+δ)+ ions is found to be 4.6 and polyhedron is intermediate between tetrahedral and octahedral.

A High‐Detectivity, Fast‐Response, and Radiation‐Resistant TiN/CdZnTe Heterojunction Photodiode

AbstractA novel high‐performance ultraviolet–visible–near‐infrared (300–820 nm) heterojunction photodiode based on radiation‐resistant semiconductor materials is proposed. A titanium nitride (TiN) “window” layer is deposited via magnetron sputtering onto a cadmium zinc telluride (CdZnTe) solid solution single crystal. The TiN/CdZnTe heterojunction photodiodes concurrently reveal an outstanding detectivity, response time, and linear dynamic range outperforming similar heterojunction photodiodes and photodetectors, based on photoactive inorganic compound semiconductor materials. Moreover, the added feature of the proposed heterojunction photodiodes is their excellent radiation resistance, experimentally demonstrated under short impulse proton irradiation (170 keV) with an accumulated fluence of 2 × 1012 proton cm−2. This unusual synergy of high performance and advanced radiation resistance of the TiN/CdZnTe photodiodes provides a unique platform for operation in space or radioactively contaminated environments.

New insight into lithium-containing ternary compound based on barium gadolinium molybdate

In this work, a part of BaMoO4-Gd2(MoO4)3–Li2MoO4 ternary system has been investigated. It has been shown that the ternary compounds formed in the system are solid solutions based on BaGd2(MoO4)4 with 0–90% filling of cationic vacancies as the lithium content in the solid solution increases. XRD and Raman studies have been carried out, and the possibilities of growing solid solution single crystals of various compositions have been determined. Neodymium doped solid solution single crystals has been grown and optical absorption spectra has been analysed.

Deformation mechanisms in single crystal Ni-based concentrated solid solution alloys by nanoindentation

Nanoindentation is a critical technique to probe mechanical properties at the micrometer and sub-micrometer scales, accompanied by challenges from indentation size effect, pile-up/sink-in effect, and strain rate sensitivity. In this study, different nanoindentation techniques have been employed to explore Ni-based concentrated solid solution alloys (CSAs) with the addition of 3d transition metal elements including Co, Cr, Mn, and Fe, including unique single-crystal Ni, NiCo, NiFe, Ni80Cr20, and NiCoFeCr samples with (100) surfaces. A procedure of nanoindentation tests and data analysis/correction have been developed, and a data set of hardness, elastic modulus, strain rate sensitivity, and activation volume for Ni-based CSAs are provided, including the less explored binary alloys such as Ni80Cr20 and Ni80Mn20. The results show that the type of alloying elements is more critical than the number of elements in strengthening: Co does not provide strengthening in NiCo, while Cr, Mn, and Fe are effective strengthening elements. Cr is the most effective among all the 3d transition metal elements. Furthermore, atomic-level lattice distortion is responsible for the strengthening and the role of stacking fault energy is insignificant in Ni-based CSAs at room temperature. In summary, nanoindentation shows increasing promise as a reliable and fast tool to provide comprehensive mechanical information for new alloy design and development.

Thermal conductivity of single crystals zirconia stabilized by scandium, yttrium, gadolinium, and ytterbium oxides

The phase composition and heat conductivity of (ZrO2)0.9(R2O3)0.1 solid solution single crystals have been studied, where R = (Gd, Yb, Sc, Y), (ZrO2)0.9(Sc2O3)0.09(Gd2O3)0.01 and (ZrO2)0.9(Sc2O3)0.09(Yb2O3)0.01. Single crystals have been grown by directional melt crystallization in a cold skull. The phase composition of the crystals has been studied using X-ray diffraction and Raman spectroscopy. The heat conductivity of the crystals has been studied using the absolute steady-state technique of longitudinal heat flow in the 50—300 K range. We show that at a total stabilizing oxide concentration of 10 mol.% the phase composition of the crystals depends on the ionic radius of the stabilizing cation. The (ZrO2)0.9(Sc2O3)0.1 crystals have the lowest heat conductivity in the 50—300 K range while the (ZrO2)0.9(Gd2O3)0.1 solid solutions have the lowest heat conductivity at 300 K.Analysis of the experimental data suggests that the heat conductivity of the crystals depends mainly on the phase composition and ionic radius of the stabilizing cation. Phonon scattering caused by the difference in the weight of the co-doping oxide cation has a smaller effect on the heat conductivity.

High-quality ferroelectric Bi0.5K0.5TiO3‒BiFeO3 solid-solution single crystals grown under high-pressure oxygen atmosphere

Ferroelectric (Bi0.5K0.5)TiO3–BiFeO3 solid solutions are promising materials for high-temperature piezoelectric applications because of their high depolarization temperature. In this study, we demonstrate the successful growth of high-quality (Bi0.5K0.5)TiO3–BiFeO3 single crystals near the morphotropic phase boundary by a flux method. Crystal growth at a high oxygen pressure of 0.9 MPa drastically reduces leakage currents, which enables ferroelectric polarization switching and a piezoelectric response associated with a rotation of polar nanosized domains. This study contributes to further detailed analyses of the relationship between crystal structures and ferroelectric properties of the (Bi0.5K0.5)TiO3–BiFeO3 solid-solution system.

Thermal conductivity of single crystals zirconia stabilized by scandium, yttrium, gadolinium, and ytterbium oxides

The phase composition and heat conductivity of (ZrO2)0.9(R2O3)0.1 solid solution single crystals have been studied, where R = (Gd, Yb, Sc, Y), (ZrO2)0.9(Sc2O3)0.09(Gd2O3)0.01 and (ZrO2)0.9(Sc2O3)0.09(Yb2O3)0.01. Single crystals have been grown by directional melt crystallization in a cold skull. The phase composition of the crystals has been studied using X-ray diffraction and Raman spectroscopy. The heat conductivity of the crystals has been studied using the absolute steady-state technique of longitudinal heat flow in the 50–300 K range. We show that at a total stabilizing oxide concentration of 10 mol.% the phase composition of the crystals depends on the ionic radius of the stabilizing cation. The (ZrO2)0.9(Sc2O3)0.1 crystals have the lowest heat conductivity in the 50–300 K range while the (ZrO2)0.9(Gd2O3)0.1 solid solutions have the lowest heat conductivity at 300 K. Analysis of the experimental data suggests that the heat conductivity of the crystals depends mainly on the phase composition and ionic radius of the stabilizing cation. Phonon scattering caused by the difference in the weight of the co-doping oxide cation has a smaller effect on the heat conductivity.

Long-wavelength optical properties of the Ca0.33Sr0.33Ba0.33F2 solid solution single crystals

The optical characteristics of Ca0.33Sr0.33Ba0.33F2 (CSBF) single crystal of a ternary solid solution of calcium, strontium and barium fluorides were studied in order to create disordered optical media. Characteristics of the single crystals of individual fluorides CaF2, SrF2, BaF2 and binary solid solutions Ca0.6Sr0.4F2 and Ba0.67Sr0.33F2 were obtained. Broadband reflection and transmission spectra of the said crystals were recorded in the frequency range of 3–5000 cm−1, and the values of the complex refractive indexes and dielectric constants were calculated. The generalized four parameter model were used for calculation of absorption band parameters. For the CSBF crystal, a significant broadening of the band was observed in the absorption region at optical phonon modes along with an increased absorption in the region below the optical phonon frequencies, which is typical for disordered dielectric media.

Effect of Cobalt Content on Point Defects and Local Structure in Activated Ca3(Vo4)2 Single-Crystal Solid Solutions

Effect of Cobalt Content on Point Defects and Local Structure in Activated Ca3(Vo4)2 Single-Crystal Solid Solutions

Peculiarities of the induced phase transition in single-crystal solid solutions Na-=SUB=-1/2-=/SUB=-Bi-=SUB=-1/2-=/SUB=-TiO-=SUB=-3-=/SUB=--5 %BaTiO-=SUB=-3-=/SUB=-

The dielectric and optical properties, as well as the time dependences of the permittivity in an electric field applied along the [001] direction, are studied in Na1/2Bi1/2TiO3-5 %BaTiO3 single crystals lying near the morphotropic phase boundary. It is shown that, even in the absence of an electric field, dielectric and optical hysteresis associated with the coexistence of tetragonal and rhombohedral phases is observed in a wide temperature range, and the relative volume fractions of the two phases largely depend on temperature. It was found that at temperatures below the temperature of the morphotropic phase transition, the induction of the ferroelectric phase occurs without a delay time, which distinguishes the samples under study from PbMg1/3Nb2/3O3-xPbTiO3 solid solutions. The results obtained are explained by different sizes of polar nanoregions in the low-temperature phase. Keywords: ferroelectricity, relaxors, induced phase transition.

Surface-barrier structures based on solid solutions (In <sub>2 </sub>S <sub>3 </sub>) <sub>х </sub>•(AgIn <sub>5 </sub>S <sub>8 </sub>) <sub>1–х </sub>

Single crystals of solid solutions (In2S3)x⋅ (AgIn5S8)1–x were grown by the method of directional crystallization of the melt (Bridgman method). Studies of the elemental composition and crystal structure of these single crystals have been carried out. On the basis of solid solutions (In2S3)x⋅ (AgIn5S8)1–x, photosensitive structures have been created for the first time and the photoelectric properties of these structures have been determined. The possibility of using the created structures as broadband photoconverters of optical radiation is shown.

Growth, Structure, and characterization of new High-TC Piezo-/Ferroelectric Bi(Zn2/3Ta1/3)O3-PbTiO3 single crystals

In this work, new bismuth-based complex perovskite piezo-/ferroelectric single crystals of the (1-x)PbTiO3-xBi(Zn2/3Ta1/3)O3 solid solution have been successfully grown by the high temperature solution method (HTSG). The crystal structure was found to be tetragonal at room temperature by means of structural analysis by X-ray diffraction and domain examination by polarized light microscopy (PLM). High Curie temperature (TC = 470 °C) was determined by dielectric measurements and PLM observations. Band-like domain structures were observed in the (001)-oriented single crystal with a width of 100–200 µm. Good piezoelectric performance (d33 = 251 pC/N) and high coercive field (EC = 30 kV/cm) were found by the piezoelectric and ferroelectric characterizations. Detailed crystal structural refinement was performed to establish the structure–property relationship in this system. Comparative studies of current bismuth-based complex perovskite solid solution single crystals point to the advantages of the Bi(Zn2/3Ta1/3)O3-PbTiO3 single crystals in terms of high TC, good piezoelectric performance, and high coercive field. These advantages make this piezo-crystal system a favourable candidate for potential high-temperature and high-power electromechanical applications.

Single crystal solid state electrolytes based on yttria, ytterbia and gadolinia doped zirconia

The effect of stabilizing oxide cation radius on the phase composition and transport properties of single crystal solid state ZrO2 electrolytes doped with Yb2O3, Y2O3 or Gd2O3 have been studied. The solid solution single crystals have been grown by directional melt crystallization in a cold crucible. The structure of the single crystals has been studied using X-ray diffraction, Raman scattering and transmission electron microscopy. We show that the formation of the cubic solid solution depends on the concentration of stabilizing oxide and the ionic radius of stabilizing cation. The smaller the ionic radius of the stabilizing cation, the lower the stabilizing oxide concentration at which the forming cubic phase is stable. Study of the high-temperature conductivity of the (ZrO2)1-х(R2O3)х solid solution crystals where R–Y, Yb and Gd has shown that an increase in the ionic radius of the stabilizing oxide reduces the conductivity of the crystals. The conductivity vs. concentration dependences of the crystals stabilized with Yb2O3, Y2O3 and Gd2O3 have maxima at stabilizing oxide concentrations of 8, 9 and 10 mol.%, respectively.

Ternary Hybrid Perovskite Solid Solution Single Crystals: Growth, Composition Determination and Phase Stability in Highly Moist Atmosphere.

Ternary hybrid perovskite solid solutions have shown superior optoelectronic properties and better stability than their ABX3 simple perovskite counterparts under ambient conditions. However, crystal growth and identification of the accurate composition of these complex crystalline compounds remain challenging, and their stability under extreme conditions such as in highly moist atmosphere is unknown. Herein, large-size (up to 2 cm) single crystals of ternary perovskite 0.80FAPbI3 ⋅ x'FAPbBr3 ⋅ y'CsPbI3 (x'+y'=0.20) are grown. An elemental analysis method based on wavelength dispersive X-ray fluorescence is proposed to determine their accurate compositions. Among these single crystals, the composition with y'=0.12 shows the best moisture stability at 90 % relative humidity for 15 days. Other components with richer or poorer Cs+ ions undergo different phase segregation behaviours. The performance and stability of photodetectors based on these single crystals are tested. This work offers a deeper insight into phase stability of ternary hybrid perovskite solid solution crystals in highly moist atmosphere.

High-temperature poling treatment of congruent ferroelectric LiNb0.5Ta0.5O3 solid solution single crystals

Lithium niobate and tantalate are among the most important and widely used materials of acoustooptics and acoustoelectronics. They have high piezoelectric constants enabling their use as actuators. Their use is however restricted by the thermal instability of lithium niobate crystals and the low Curie temperature TC of lithium tantalate crystals. Overcoming these drawbacks typical of some compounds is possible by growing LiNb1-xTaxO3 single crystals. Good quality LiNb1-xTaxO3 single crystals have been grown using the Czochralsky technique. High-temperature poling process of LiNb1-xTaxO3 single crystals has been studied. The main differences between the process modes required for poling of congruent LiNb1-xTaxO3 single crystals and congruent LiNbO3 single crystals have been demonstrated. Parameters of high-temperature electric diffusion processing of LiNb1-xTaxO3 single crystals that provide for singledomain crystals for further study of physical properties have been reported.