Solid-state Single Crystal Growth Research Articles

Top-seeded solid-state single crystal growth of 0.75(Na0.5Bi0.5)TiO3-0.25SrTiO3 single crystals in oxygen and their characterization

Top-seeded solid-state single crystal growth of 0.75(Na0.5Bi0.5)TiO3-0.25SrTiO3 single crystals in oxygen and their characterization

On the growth and characterization of SmOFe[formula omitted]Co[formula omitted]As single crystals

In this work we report the crystal growth of SmOFe1−xCoxAs single crystals with Co content 0≤x≤0.25 via the solid-state single crystal growth method at ambient pressure. The centrepiece of this method is to trigger the abnormal grain growth process, where only a small amount of grains grows significantly larger than the majority of grains. In its extreme case, this diffusion-controlled process in the solid state may foster large and three-dimensional crystals that grow out of a polycrystalline matrix. Since most parameters known to trigger solid-state single crystal growth are known only empirically, we discuss in detail which are the optimal parameters for the growth of SmOFe1−xCoxAs single crystals and rationalize the mechanisms that may be relevant to activate the diffusion-driven solid-state single crystal growth in the system under study. The plate-like crystals show distinct facets, which is a common feature of crystals grown by this method, with lateral dimensions of up to 4.8mm and a thickness of up to 0.06mm. The single crystals of this series as well as the corresponding polycrystals were characterized and compared regarding their crystal structure, chemical composition, morphology as well as magnetic and superconducting properties. Interestingly, our characterization data suggest a solubility gap for high Co contents. This finding is supported by comparing with previous reports, albeit existence of a solubility gap is not discussed therein. As expected across the series, charge doping suppresses the structural and magnetic transitions until for 5% Co content superconductivity is established. In particular, the splitting and clear differentiation of the structural and subsequent magnetic transition is rarely seen for REOFeAs compounds, but well resolved for the Fe-rich SmOFe1−xCoxAs single crystals and even for the x=0.0125 crystal, but smeared out for the corresponding polycrystalline samples. Hence, the SmOFe1−xCoxAs single crystal presented in this work are of exceptional high quality.

Comparison of (K0.5Na0.5)NbO3 Single Crystals Grown by Seed-Free and Seeded Solid-State Single Crystal Growth.

(K0.5Na0.5)NbO3-based piezoelectric ceramics are of interest as a lead-free replacement for Pb(Zr,Ti)O3. In recent years, single crystals of (K0.5Na0.5)NbO3 with improved properties have been grown by the seed-free solid-state crystal growth method, in which the base composition is doped with a specific amount of donor dopant, inducing a few grains to grow abnormally large and form single crystals. Our laboratory experienced difficulty obtaining repeatable single crystal growth using this method. To try and overcome this problem, single crystals of 0.985(K0.5Na0.5)NbO3-0.015Ba1.05Nb0.77O3 and 0.985(K0.5Na0.5)NbO3-0.015Ba(Cu0.13Nb0.66)O3 were grown both by seed-free solid-state crystal growth and by seeded solid-state crystal growth using [001] and [110]-oriented KTaO3 seed crystals. X-ray diffraction was carried out on the bulk samples to confirm that single-crystal growth had taken place. Scanning electron microscopy was used to study sample microstructure. Chemical analysis was carried out using electron-probe microanalysis. The single crystal growth behaviour is explained using the mixed control mechanism of grain growth. Single crystals of (K0.5Na0.5)NbO3 could be grown by both seed-free and seeded solid-state crystal growth. Use of Ba(Cu0.13Nb0.66)O3 allowed a significant reduction in porosity in the single crystals. For both compositions, single crystal growth on [001]-oriented KTaO3 seed crystals was more extensive than previously reported in the literature. Large (~8 mm) and relatively dense (<8% porosity) single crystals of 0.985(K0.5Na0.5)NbO3-0.015Ba(Cu0.13Nb0.66)O3 can be grown using a [001]-oriented KTaO3 seed crystal. However, the problem of repeatable single crystal growth remains.

Effect of ZrO2 doping on the growth of lead-free piezoelectric 0.75(Bi1/2Na1/2)TiO3-0.25SrTiO3 single crystals by solid-state single crystal growth

Single crystals of 0.75(Bi1/2Na1/2)TiO3-0.25SrTiO3 have potential for use in piezoelectric actuators because of their large values of electric field-induced strain. Single crystals of 0.75(Bi1/2Na1/2)TiO3-0.25SrTiO3 have been prepared by solid-state single crystal growth, but growing large crystals is difficult due to matrix grain growth. Previous experiments with 0.95(Bi1/2Na1/2)TiO3-0.05BaTiO3 showed that doping with ZrO2 reduced matrix grain growth but also reduced single crystal growth. In this work, 0.75(Bi1/2Na1/2)TiO3-0.25SrTiO3 is doped with small amounts of ZrO2 and the effect on both single crystal and matrix grain growth is examined. ZrO2 addition has a minor effect on single crystal and matrix grain growth.

Solid-state single-crystal growth of YAG and Nd: YAG by spark plasma sintering

• Growth of YAG and Nd:YAG single crystals achieved during the spark plasma sintering. • Porosity of the single crystals reduced due to the application of external pressure. • High Nd 3+ doping had a positive effect on the single-crystal conversion kinetics. Recent studies have shown that many challenges encountered in conventional single crystal growth methods, including high production costs, can be overcome by using the solid-state single-crystal growth (SSCG) approach, which has been recognized as a simple and cost-effective alternative for obtaining single crystals. In this work, Y 3 Al 5 O 12 (YAG) and Nd 3+ -doped YAG (Nd:YAG) single crystals were grown via the SSCG method using spark plasma sintering (SPS). The growth of single crystals was initiated at the surface of (110) YAG single-crystal seeds embedded inside YAG and Nd:YAG powder beds, and this growth continued as the surrounding polycrystalline matrix was converted into a single crystal. The application of external pressure during the SPS process has been found beneficial for reducing the porosity of the grown single crystals. Moreover, high Nd 3+ doping levels had a positive effect on the conversion kinetics, with a growth rate of almost 50 µm/h, which increased the driving force for single-crystal growth through the solute drag effect. EDS elemental mapping and line scans confirmed the compositional uniformity of the grown single crystals, while EBSD images verified their crystallization in the (110) direction. The obtained results confirm the strong potential of the SSCG technique coupled with SPS for the growth of undoped and highly doped YAG single crystals with excellent quality.

“Generation III” Piezoelectric Single Crystals Developed by Solid-State Single Crystal Growth Method

Crystallographically engineered Relaxor-PT single crystals, specifically PMN-PT (Generation I) and PIN-PMN-PT/PMN-PZT (Generation II), offer much higher piezoelectric and electromechanical coupling coefficients (d33&gt;1,500 pC/N, k33&gt;0.9), when compared to polycrystalline PZT-5H ceramics (d33&gt;600 pC/N, k33&gt;0.75). Recently Ceracomp Co., Ltd. (www.ceracomp.com) has developed the solid-state single crystal growth (SSCG) technique and successfully fabricated Gen III PMN-PZT single crystals modified with acceptors or donors. The piezoelectric constants (d33) of (001) Gen III PMN-PZT single crystals were measured to be higher than 4,000 pC/N and thus about two times higher than those of PMN-PT/PZN-PT (Gen I) and PIN-PMN-PT/PMN-PZT (Gen II) single crystals. The Gen III PMN-PZT single crystals have been firstly applied to single crystal-epoxy composites, ultrasonic transducers, piezoelectric sensors, and piezoelectric actuators. In this paper we introduce the development of Gen III PMN-PZT single crystals, piezoelectric composites and multilayer single crystal actuators.

In situ total strain measurements revealing the strain mechanism of Pb(Mg1/3Nb2/3)O3[sbnd]PbTiO3 single crystals

The strain behavior of 0.71 Pb(Mg1/3Nb2/3)O3-0.29 PbTiO3 (PMN-PT) single crystal prepared by a solid-state single crystal growth method was investigated on two most widely used orientations, i.e., (001)- and (011)-oriented. A special emphasis was put on the correlation among longitudinal and transverse strains and the consequent volume change. We show that seemingly different strain behavior of (001)- and (011)-oriented crystals has the same origin, and the underlying mechanism excludes possible contribution from the frequently cited polarization rotation. In situ monitoring of electric field induced Poisson’s ratio further suggested that the polarization vectors contributing to the strain properties in PMN-PT are not confined to a unique direction forced by the crystallographic symmetry but possess a span of angular range.

Formation of ceramic and crystal claddings for a Ti:sapphire crystalline fiber core

We describe the fabrication and characterization of single-mode Ti:sapphire crystalline fibers, cladded by dip coating and high-temperature sintering at 1750 o C. Solid-state single crystal growth was observed at the perimeter of the crystalline core, and the growth speed along ( 1 1 ¯ 0 ) is about 2.7 times faster than that of (001). The grown cladding was single-crystalline as evidenced by electron backscattered diffraction and scanning electron microscopy examinations. From optical transmission measurement at 1550 nm, the far-field distribution of the transmitted light matches well with that of the fundamental mode. With a core size of 30 µm, the refractive index difference between core and clad was measured to be 1.0 × 10−4. From fluorescence mapping on the fiber end face, a very limited amount of the Ti3+ ions in core were diffused into the grown crystalline cladding during the solid-state growth.

Enhanced Mechanical Quality Factor of 32 Mode Mn Doped 71Pb(Mg1/3Nb2/3)O3–29PbZrTiO3 Piezoelectric Single Crystals

The solid solution of relaxor and lead titanate single crystals have been an excellent choice for electromechanical applications such as energy harvesters, SONARs, transducers, and biomedical equipment. The mechanical quality factor (Qm) plays a crucial role in such applications using high power resonance condition. In this work, 32 mode (011) oriented along thickness direction, Generation-III piezoelectric single crystals based on PMN-PZT [71Pb(Mg1/3Nb2/3)O3–29PbZrTiO3] have been grown by solid state single crystal growth method. The Mn doping concentration in the crystals were systematically controlled within the range of 0 to 1.0 mol.%. The piezoelectric properties noticeably varied with the Mn doping concentration when the content is over 0.1 mol.%. In order to obtain significant enhancement in Qm in PMN-PZT single crystals, especially, the Mn doping concentration should be higher than 0.7 mol.% (which offers highest figure of merit) for high power resonance applications.

Precursor Phenomena of Barium Titanate Single Crystals Grown Using a Solid-State Single Crystal Growth Method Studied with Inelastic Brillouin Light Scattering and Birefringence Measurements.

The nature of precursor phenomena in the paraelectric phase of ferroelectrics is one of the main questions to be resolved from a fundamental point of view. Barium titanate (BaTiO3) is one of the most representative perovskite-structured ferroelectrics intensively studied until now. The pretransitional behavior of BaTiO3 single crystal grown using a solid-state crystal growth (SSCG) method was investigated for the first time and compared to previous results. There is no melting process in the SSCG method, thus the crystal grown using a SSCG method have inherent higher levels of impurity and defect concentrations, which is a good candidate for investigating the effect of crystal quality on the precursor phenomena. The acoustic, dielectric, and piezoelectric properties, as well as birefringence, of the SSCG-grown BaTiO3 were examined over a wide temperature range. Especially, the acoustic phonon behavior was investigated in terms of Brillouin spectroscopy, which is a complementary technique to Raman spectroscopy. The obtained precursor anomalies of the SSCG-grown BaTiO3 in the cubic phase were similar to those of other single crystals, in particular, of high-quality single crystal grown by top-seeded solution growth method. These results clearly indicate that the observed precursor phenomena are common and intrinsic effect irrespective of the crystal quality.

Effect of Mn on Dielectric and Piezoelectric Properties of 71PMN-29PT [71Pb(Mg1/3Nb2/3)O3-29PbTiO3] Single Crystals and Polycrystalline Ceramics

In order to investigate the effect of Mn on the dielectric and piezoelectric properties of PMN-PT [Pb(Mg1/3Nb2/3)O3-PbTiO3], four different types of 71PMN-29PT samples were prepared using the solid-state single crystal growth (SSCG) method: (1) Undoped single crystals, (2) undoped polycrystalline ceramics, (3) Mn-doped single crystals, and (4) Mn-doped polycrystalline ceramics. In the case of single crystals, the addition of 0.5 mol% Mn to PMN-PT decreased the dielectric constant (K3T), piezoelectric charge constant (d33), and dielectric loss (tan δ) by about 50%, but increased the coercive electric field (EC) by 50% and the electromechanical quality factor (Qm) by 500%, respectively. The addition of Mn to PMN-PT induced an internal bias electric field (EI) and thus specimens changed from piezoelectrically soft-type to piezoelectrically hard-type. This Mn effect was more significant in single crystals than in ceramics. These results demonstrate that Mn-doped 71PMN-29PT single crystals, because they are piezoelectrically hard and simultaneously have high piezoelectric and electromechanical properties, have great potential for application in fields of SONAR transducers, high intensity focused ultrasound (HIFU), and ultrasonic motors. Key words: Piezoelectric, Single Crystal, 71PMN-29PT, Mn Doping, Ultrasonic Transducer

Solid state single crystal growth of three-dimensional faceted LaFeAsO crystals

Solid state single crystal growth (SSCG) is a crystal growth technique where crystals are grown from a polycrystalline matrix. Here, we present single crystals of the iron pnictide LaFeAsO grown via SSCG using NaAs as a liquid phase to aid crystallization. The size of the as-grown crystals are up to 2 × 3 × 0.4 mm3. Typical for this method, but very uncommon for crystals of the pnictide superconductors and especially for the oxypnictides, the crystals show pronounced facets caused by considerable growth in c direction. The crystals were characterized regarding their composition, structure, magnetic, and thermodynamic properties. This sets the stage for further measurements for which single crystals are crucial such as any c axis and reciprocal space dependent measurements.

Strong and anisotropic magnetoelectricity in composites of magnetostrictive Ni and solid-state grown lead-free piezoelectric BZT–BCT single crystals

Aimed at developing lead-free magnetoelectric (ME) composites with performances as good as lead (Pb)-based ones, this study employed (001) and (011) oriented 82BaTiO3-10BaZrO3-8CaTiO3 (BZT–BCT) piezoelectric single crystals, fabricated by the cost-effective solid-state single crystal growth (SSCG) method, in combination with inexpensive, magnetostrictive base metal Nickel (Ni). The off-resonance, direct ME coupling in the prepared Ni/BZT–BCT/Ni laminate composites was found to be strongly dependent on the crystallographic orientation of the BZT–BCT single crystals, as well as the applied magnetic field direction. Larger and anisotropic ME voltage coefficients were observed for the composite made using the (011) oriented BZT–BCT single crystal. The optimized ME coupling of 1 V/cm Oe was obtained from the Ni/(011) BZT–BCT single crystal/Ni composite, in the d32 mode of the single crystal, when a magnetic field was applied along its [100] direction. This performance is similar to that reported for the Ni/Pb(Mg1/3Nb2/3)O3-Pb(Zr,Ti)O3 (PMN–PZT) single crystal/Ni, but larger than that obtained from the Ni/Pb(Zr,Ti)O3 ceramic/Ni composites. The results of this work demonstrate that the use of lead-free piezoelectric single crystals with special orientations permits the selection of desired anisotropic properties, enabling the realization of customized ME effects in composites.

Improved solid-state conversion and piezoelectric properties of 90Na1/2Bi1/2TiO3-5BaTiO3-5K1/2Na1/2NbO3 single crystals

Na1/2Bi1/2TiO3-BaTiO3-K1/2Na1/2NbO3 (NBT-BT-KNN) is a promising candidate system for actuator applications in lead-free piezoelectric materials because of its large electric-field-induced strain. We were able to fabricate 96.9% dense 90NBT-5BT-5KNN (mol%) single crystals by the solid-state single crystal growth technique using sintered pellets and SrTiO3 seed crystals. The fabricated single crystals with a 〈001〉 direction exhibited high piezoelectric performance with a large strain of 0.67% and a high converse piezoelectric constant (Smax/Emax) of about 1670 pm/V at 4kV/mm. These values are much higher than those previously reported for ceramics, 0.45% and 560 pm/V at 8kV/mm, and for single crystals, 0.57% and 950 pm/V at 6kV/mm, of the NBT-BT-KNN system. The measured piezoelectric properties are even comparable with those of lead-containing piezoelectric single crystals, which demonstrates high applicability of the fabricated NBT-5BT-5KNN single crystals for actuators.

Dielectric and Piezoelectric Properties of “Lead-free” Piezoelectric Rhombohedral Ba(Ti0.92Zr0.08)O3 Single Crystals

Rhombohedral Ba(Ti 0.92 Zr0.08)O₃ single crystals are fabricated using the cost-effective solid-state single crystal growth (SSCG) method; their dielectric and piezoelectric properties are also characterized. Measurements show that (001) Ba(Ti 0.92 Zr 0.08 )O₃ single crystals have an electromechanical coupling factor (k 33 ) higher than 0.85, piezoelectric charge constant (d 33 ) of about 950 [pC/N], and piezoelectric voltage constant (g 33 ) higher than 40 [x10 -3 Vm/N]. Especially the d 33 of (001) Ba(Ti 0.92 Zr 0.08 )O₃ single crystals was by about six times higher than that of their ceramics. Because their electromechanical coupling factor (k 33 ) and piezoelectric voltage constant (d 33 , g 33 ) are higher than those of soft PZT ceramics, it is expected that rhombohedral (001) Ba(Ti 0.92 Zr 0.08 )O₃ single crystals can be used as “lead-free” piezoelectric materials in many piezoelectric applications such as actuator, sensor, and transducer.

Solid-state conversion of (94-x)(Na1/2Bi1/2)TiO3-6BaTiO3-x(K1/2Na1/2)NbO3 single crystals and their enhanced converse piezoelectric properties

(94-x)(Na1/2Bi1/2)TiO3-6BaTiO3-x(K1/2Na1/2)NbO3 (NBT-6BT-xKNN) piezoelectric ceramics have notable potential for replacing lead containing piezoelectric ceramics in actuator applications due to their exceptionally large strain. However, a high electric field for producing a large strain and a large hysteresis are critical issues that should be resolved for practical actuator applications. In an attempt to address these issues and optimize the piezoelectric performance, we fabricated NBT-6BT-xKNN (x = 0 - 5) piezoelectric single crystals with a size of 8 x 8x 10 mm by the solid-state single crystal growth method and systematically measured their electrical properties. With increased addition of KNN to replace NBT, the ferroelectricity and piezoelectricity of the fabricated [001] NBT-6BT-xKNN single crystals decreased, but their unipolar strain and hysteresis were considerably improved. For NBT-6BT-5KNN single crystals, the largest maximum strain (Smax) was 0.57% at 6 kV/mm, showing a converse piezoelectric constant (Smax/Emax) of 950 pm/V, and their hysteresis in the unipolar S-E curve was 12% at 6kV/mm, which would be appropriate for some actuator applications. Our results demonstrate the applicability of the produced single crystals as lead-free piezoelectric actuator components.

압전 PMN-PZT 단결정의 유전 및 압전 특성에 미치는 전극 종류의 영향

The effect of the electrode type on the dielectric and piezoelectric properties of Pb(Mg 1/3 Nb 2/3 )O₃-PbZrO₃-PbTiO₃ (PMN-PZT) single crystals was investigated in an effort to improve their properties for various piezoelectric applications. First, three different types of PMN-PZT single crystals [PMN-PZT-A (piezoelectrically soft type; dielectric constant ~ 10,000), PMN-PZT-B (piezoelectrically soft type; phase-transition temperature between the rhombohedral and tetragonal phases (T RT ) ~ 145℃), PMN-PZT-C (piezoelectrically hard type; high mechanical quality factor (Q m ) ~ 1,000)] were fabricated using the solid-state single crystal growth (SSCG) method. Then, four different types of electrodes [sputtered Au, sputtered Cr/Au, sputtered Ti/Au, and fired Ag] were formed on the single crystals, and their dielectric and piezoelectric properties were measured. The single crystals with a sputtered Ti/Au electrode showed the highest dielectric and piezoelectric constants but the lowest coercive electric field (E C ). The single crystals with a fired Ag electrode showed the lowest dielectric and piezoelectric constants but the highest coercive electric field (E C ). This dependence on the type of electrode was most significant in the piezoelectrically hard PMN-PZT-C single crystals. However, the effects of the electrode type on the phase transition temperatures (T C , T RT ) and dielectric loss were negligible. These results clearly demonstrate that it is important to select an appropriate electrode so as to maximize the dielectric and piezoelectric properties of single crystals in each type of piezoelectric application.

Solid‐State Conversion of Single Crystals: The Principle and the State‐of‐the‐Art

Solid‐state conversion of single crystals from polycrystalline materials has the advantages of cost‐effectiveness, chemical homogeneity, and versatility over the conventional melt growth and solution growth methods, particularly for systems with high melting points, incongruent melting, high reactivity (volatility), and phase transformations at high temperature. Nevertheless, for commercial production, this technique has only been successful in a few limited systems, in particular ferroelectric systems. This is mostly because of the difficulty in controlling the microstructure, particularly suppressing grain growth in the polycrystal during its conversion. This article describes the principle and the current status of the solid‐state conversion of single crystals. We first introduce the recently developed principle of microstructural evolution to explain the basis of the microstructure control in polycrystals for solid‐state conversion. We then report recent technical developments in fabricating single crystals by the solid‐state single crystal growth (SSCG) method and their physical properties. The SSCG method is expected to be studied and utilized more widely in fabricating single crystals with complex compositions as a strong alternative to the melt growth and solution growth methods.

0.8 이상의 전기기계결합계수(k33)를 가지는 고효율 무연 압전 Ba(Ti0.94Zr0.06)O3단결정

Orthorhombic Ba(Ti 0.94 Zr 0.06 )O₃ single crystals are fabricated using the cost-effective solid-state single crystal growth (SSCG) method; their dielectric and piezoelectric properties are also characterized. Measurements show that (001) Ba(Ti 0.94 Zr 0.06 )O₃ single crystals have an electromechanical coupling factor (k 33 ) higher than 0.83, piezoelectric charge constant (d 33 ) of about 400 [pC/N], and piezoelectric voltage constant (g 33 ) higher than 50 [x10 -3 Vm/N]. The transition temperature (TOT) of the (001) Ba(Ti 0.94 Zr 0.06 )O₃ single crystals between orthorhombic and tetragonal phases is also observed to be about 61℃. Because their electromechanical coupling factor (k 33 ) and piezoelectric voltage constant (g 33 ) are higher than those of soft PZT ceramics, it is expected that (001) Ba (Ti 0.94 Zr 0.06 )O₃ single crystals can be used as “lead-free” piezoelectric materials in many piezoelectric applications.

001] 및 [011] 방향 분극의 압전 단결정 PMN-PZT를 이용한 진동 에너지 수확 특성

This work investigated the electromechanical performance of a cantilevered vibration energy harvester incorporating the single crystal PMN-PZT, manufactured with the most recent technology of solid-state single crystal growth. The performances of single crystal PMN-PZTs with two different crystallographic axes such as [011] and [001] are compared with those of PZT ceramics. From the investigations, it is shown that the [001]-poled PMN-PZT is advantageous for the excitations containing single dominant frequency component, while the single crystal [011]-<TEX>$d_{32}$</TEX> is superior in terms of the energy storage density and energy conversion efficiency.