Solid-state Crystal Growth Method Research Articles

Self-poling and DC poling of Mn doped Pb(Mg1/3Nb2/3)O3-Pb(ZrTi)O3 single crystals grown by a solid state crystal growth process

Acceptor Mn-doped Pb(Mg1/3Nb2/3)O3-Pb(ZrTi)O3 (PMN-PZT) single crystals (SCs) grown by a solid state crystal growth (SSCG) process electrode with Ag at 650 °C showed a high piezoelectric coefficient (d 33) of 520 pC N−1 at 25 °C by self-poling, i.e. without any additional poling process. Upon heating above the Curie temperature (T c), the impedance characteristics’ oscillation peak due to piezoelectricity disappears. However, as the temperature falls below T c, these oscillation peaks reemerge around T c. And when the temperature is further lowered to around RT, the impedance characteristics return to almost the original state. The d 33 values of the non-poled SCs, initially 520 pC N−1, increased to 910 pC N−1 after DC poling (DCP) and to 1170 pC N−1 after field cooling (FC)-DCP. These values surpass those of commercially available high-Qm PZT ceramics. These high-Qm PMN-PZT single crystals developed using the SSCG method demonstrate huge potential for future transducer applications.

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.

Ultrahigh-performance [001]-oriented porous PZT-5H single crystal grown by the solid state crystal growth method

Porous PZT-5H single crystals are grown by the solid state crystal growth (SSCG) method. The microstructure, phase structure and dielectric/piezoelectric properties are investigated for [001]-oriented porous PZT-5H single crystal. Evolution of phase structure with temperature is researched using in-situ temperature-dependent X-ray diffraction. The effect of pores on performance parameters is simulated using COMSOL Multiphysics® software. Ultrahigh piezoelectric coefficient d33 of up to about 1700 pC/N and effective piezoelectric coefficient d33* of up to about 3700 pm/V at 5 kV/cm are obtained. Moreover, the effective piezoelectric coefficient d33* is stable around 1900 pm/V under 3 kV/cm and 5 kV/cm in the temperature range of 70–160 °C. Importantly, the sample possess an extremely large figure of merit g33*d33 (111 × 10−12 m2/N), which is related to the presence of pores in the single crystal. This work expands the scope of PZT based single crystal and highlights their significant application possibilities in piezoelectric energy harvester, and actuator at high temperature.

Growth and enhanced electrical properties of PIN-PMN-PT piezoelectric single crystal grown by the solid-state crystal growth method

0.32Pb(In1/2Nb1/2)O3-0.335Pb(Mg1/3Nb2/3)O3-0.345PbTiO3 single crystals were successfully grown by a solid-state crystal growth (SSCG) method through precise control of the key growth parameters. The effects of the sintering temperature and the soaking time on the growth of the PIN-PMN-PT single crystals were investigated. The growth distance is up to 1069 µm for [110]-oriented PIN-PMN-PT single crystal grown at 1150 °C for 50 h. The microstructure, crystal structure and dielectric, ferroelectric and piezoelectric properties were systematically investigated for the SSCG-grown [110]-oriented PIN-PMN-PT single crystals. The [110]-oriented PIN-PMN-PT single crystals exhibit high piezoelectric properties (d33 ∼ 1041pC/N, d33 * ∼ 1024 pm/V), Curie temperature (TC ∼ 250 °C) and ferroelectric properties (EC ∼ 8.4 kV/cm and Pr ∼33 μC/cm2). Further, the [001]-oriented single crystals also possess outstanding piezoelectric properties (d33 ∼ 1004pC/N, d33 * ∼ 1203 pm/V), Curie temperature (TC ∼ 266 °C) and ferroelectric properties (EC ∼ 9.7 kV/cm and Pr ∼36 μC/cm2), which are much superior to those of counterpart ceramics.This work opens the door of growth of PIN-PMN-PT single crystals by SSCG method and the SSCG-grown PIN-PMN-PT single crystals are very promising candidates for high performance electromechanical devices with wide temperature and electric field application.

Enhanced electrical properties by AC poling of relaxor-Pb(Zr,Ti)O3 single crystals manufactured by the solid state crystal growth method

An exceptionally large free dielectric permittivity of 14200, piezoelectric coefficient (d 33) of 4800 pC/N and calculated electromechanical coupling factor k 33 of 95.7% were obtained from Pb(Mg1/3Nb2/3)O3 (PMN) - Pb(Zr,Ti)O3 (PZT) single crystals (SCs) under AC poling (ACP). The PMN −0.3PZT SCs grown by a solid-state crystal growth (SSCG) method with high composition uniformity showed a phase change temperature of 57 °C–72 °C and Curie temperature T c of 140 °C. The measured d 33 of 250 pC/N was obtained after a heat treatment at 250 °C, which is 110 °C higher than the T c of the SC. Microstructural observations revealed that the ACP SC showed a different 109° domain wall layers morphology due to the presence of some pores, which is dissimilar to the Bridgman ACP relaxor-PbTiO3 SCs. These outstanding piezoelectric properties, heat durability, lower acoustic impedance, and better machinability of ACP SSCG SCs are promising for future piezoelectric device applications.

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.

Conditions of large unitary (K, Na)NbO3 system single crystals for rapid solid-state crystal growth method

To expand the process window for the rapid solid-state crystal growth (RSSCG) method, through which large unitary single crystals of a (K0.5Na0.5)NbO3 (KNN) system can be synthesized in a short time, we varied the dominant fabrication parameters, the B-site excess ratio and the Bi2O3 content, over a range wider than that utilized in previous studies. Unitary single crystals were obtained at the B-site excess ratios of 0.75%–1.75%; particularly, 1.00% and 1.25% were found to be suitable for the synthesis. Electron spin resonance analysis showed that the concentration of oxygen vacancies increased with increasing B-site excess ratios and decreased with increasing amount of added Bi2O3 in the calcined powder. The optimization of the critical driving force for crystal growth by controlling oxygen vacancy concentration was found to be key to growing the large unitary single crystals appropriately by the RSSCG method.

Giant piezoelectric properties of the [110]-oriented PZT-5H single crystals grown by solid state crystal growth

An ultrahigh piezoelectric performance (d33 ∼ 1800 pC N−1 and ∼ 2400 pm V−1 at 3 kV cm−1, k33 ∼ 87%) is achieved in the [110]-oriented PZT-5H single crystals grown using the solid state crystal growth method with excess PbO addition.

Effects of MnO2-doping on growth, structure and electrical properties of lead-free piezoelectric K0.5Na0.5NbO3-BiAlO3 single crystals

K0.5Na0.5NbO3 (KNN)-based lead-free piezoelectric single crystals have been prepared by the Seed-Free, Solid-State Crystal Growth (SFSSCG) method, and the effects of MnO2 doping on the structural and electrical properties were systematically investigated. The results showed that the MnO2-doping can promote the growth of K0.5Na0.5NbO3-BiAlO3 (KNN-BA) single crystals and enhance its electrical properties. Furthermore, the size of the (1 - x)( KNN-BA)-xMnO2 crystals reached the maximum value of about 18 × 17 × 2 mm3 at x = 0.005. Also, the color of the crystals did gradually change, from light yellow to dark brown, due to the addition of MnO2. The XRD and refinement results showed that the addition of MnO2, in the range of 0 ≤ x ≤ 0.009, did not change the crystalline structure of the perovskite crystals. A two-phase perovskite crystalline structure was present in all crystals: an orthorhombic and a tetragonal phase. The content of the orthorhombic phase decreased, while the content of the tetragonal phase increased, with an increase in the MnO2 content. In addition, the domains in the crystals were mainly composed of 180° ones and had a parallel lamellar structure. Also, the smallest average domain width was obtained for crystals with x = 0.003. These crystals had the largest piezoelectric constant of 568 pC/N and an excellent overall performance of d33 = 568 pC/N, Pr = 32.2 μC/cm2, Qm = 55.3, kt = 0.36, kp = 0.39, TC = 418 °C, εr = 430, and tan δ = 0.015.

Effects of Cu addition on rapid solid-state crystal growth of (K,Na)NbO3 single crystals

We investigated the effects of 0.5 mol% to 6.0 mol% CuO addition on crystal growth by the rapid solid-state crystal growth method to synthesize large unitary rectangular (K,Na)NbO3 (KNN) single crystals several square centimeters within 24 h. X-ray photoelectron spectroscopy and X-ray powder diffraction measurements revealed that CuO and Cu2O segregated in the region near the coarsened single crystal/polycrystal boundary. A positive correlation between crystal growth and the addition of CuO up to 1.5 mol% was observed; however, for CuO amounts larger than 1.5 mol%, this correlation became negative. To investigate these phenomena, a high-precision synchrotron powder diffraction measurement was performed. Significant precipitation of the CuO phase was detected in the calcined powders with a CuO addition larger than 1.5 mol%. The effects of this precipitation on the growth mechanism for coarsening the single crystals were discussed.

(INVITED)Magneto-optical performance of (LuTb)3Al5O12 single crystal by SSCG method

High quality LuTAG [(Lu0.1Tb0.9)3Al5O12] single crystal was successfully synthesized by SSCG (Solid State Crystal Growth) method using <100>YAG (Y3Al5O12) seed crystals for the first time. The growth rate of the LuTAG single crystal is > 2 mm/h, and residual pores and birefringence cannot be detected inside the material. At a wavelength of 633 nm, a sample with a thickness of 7 mm has an inline transmittance of 81.5%, an optical loss of 0.06%/cm, and an extinction ratio of >35 dB, hence the optical quality is particularly excellent. The Verdet constant of this material at 1064 nm was 51 rad T−1m−1, which was 1.4 times that of the commercially available TGG (Tb3Ga5O12) single crystal.

Microstructure and electrical properties of CuO-doped K0.5Na0.5NbO3-based single crystals with low dielectric loss

CuO-doped K0.5Na0.5NbO3 (KNN)-based lead-free piezoelectric single crystals were realized by using a seed-free solid-state crystal growth (SFSSCG) method. The effect of the CuO addition on the single-crystal growth, microstructure and electrical properties of the systems was studied systemically. The addition of CuO is beneficial for the growth of the KNN-based crystals and decreases the width of ferroelectric domains of the crystals. In particular, the CuO doping significantly reduces the dielectric loss of the crystals. The lowest dielectric loss tanδ of 1% was achieved for the CuO-doped crystals with high piezoelectric constant and Curie temperature. The study on the leakage behavior of the crystals shows that the main electrical conduction mechanism is the space-charge-limited-current (SCLC). A coexisting crystalline structure with orthorhombic and tetragonal phases forms in the (1 − x)[KNN-LiBiO3]-xCuO crystals at x = 0.007–0.009. The growth kinetics and mechanism of the crystals were also investigated.

Effects of the calcined temperature of ingredients on the growth, structure and electrical properties of (K0.5Na0.5)NbO3-based single crystals

Lead-free K0.5Na0.5NbO3 (KNN)-based single crystals have been prepared by a seed-free, solid-state crystal growth method. The effects of the calcined temperature of ingredients on the growth, structure and electrical properties of the single crystals are systematically studied. Results show that increasing the calcined temperature is beneficial to the synthesis of pure orthorhombic-phase powder, but it hardly affects the phase structure of the single crystals. When the calcined temperature is in the range of 700–850 °C, it is more useful for obtaining larger KNN-based crystals. What is more, the width of the domains in the crystals first decreases and then increases with rising of the calcined temperature, which is in well agreement with the changing regularity of the structure and electrical properties. The single crystals with good electrical properties can be obtained in a wide calcined-temperature range of 700–850 °C: the piezoelectric constant d33 of 155–209 pC N−1, dielectric constant e of 291–389, dielectric loss tanδ of 2.0–3.4%, and remnant polarization Pr of 25.4–49.1 μC cm−2.

Growth of large unitary (K,Na)NbO3 single crystals using a seed-free solid-state crystal growth method by adjusting the B-site excess ratios and additional Bi2O3

We adjusted the B site excess ratio and the quantity of additional Bi2O3 in the KNN calcined powder in order to establish a process to fabricate, (K,Na)NbO3 (KNN)-based single crystals, with large and uniform configurations and relatively stable low porosity, using the seed-free solid-state crystal growth method. When the activity of abnormal grain growth during sample heating was controlled appropriately by adding 0.5 wt% Bi2O3 into the calcined powder with a B site excess ratio of 1%, extraordinarily large unitary rectangular single crystals were grown successfully. The individual crystals started to grow from the nucleus around the center of the green compacts formed by the calcined powder. Then they expanded until they became larger than 15 × 15 mm2 by heating at 1060 °C for 15 h. The relative density of the fabricated single crystals was higher than 99%.

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.

Effects of sintering aid and atmosphere powder on the growth of (K0.5Na0.5)NbO3 single crystals fabricated by solid-state crystal growth method

(K0.5Na0.5)NbO3 (KNN) + x (= 1, 0.5, 0.05, and 0) wt%Co3O4 single crystals were fabricated by a solid-state crystal growth method with a KTaO3 seed crystal and a KNN atmosphere powder, and the effects of the sintering aid content x and the addition of Co3O4 to the atmosphere powder on the growth of the single crystals were investigated. The formation of pores in the single crystals was suppressed by a decrease of x, which, however, decreased the crystal growth length. On the other hand, dense and large KNN single crystals could be fabricated by sintering with a KNN + 5 wt%Co3O4 atmosphere at x = 0. The dielectric, ferroelectric, and piezoelectric properties of the KNN single crystals were comparable to those of reported (K,Na)NbO3 single crystals. These results would be useful for fabricating dense and large single crystals by the solid-state crystal growth method.

Influence of trace lithium addition on the structure and properties of K0.5Na0.5NbO3-based single crystals

K0.5Na0.5NbO3 single crystal with trace amounts of lithium addition was grown by the seed-free solid-state crystal growth method. The Li addition is helpful for the growth of the crystals and improves the properties of the K0.5Na0.5NbO3 single crystals. A small amounts (0.2–0.3 at.%) of Li addition can trigger the formation of around 25% tetragonal phase. The occurrence of the phase transition may be due to the variety of the K/Na atomic ratio after Li substitution in both the Na and K sites. The optimum amount of Li addition in the crystal is 0.2–0.3 at.% in order to obtain a well performance K0.5Na0.5NbO3-based single crystal. The best electrical performance of these K0.5Na0.5NbO3-based crystals can be achieved as follows: d33 = 255 pC/N, tanδ = 1%, d*33 = 313 pm/V, and Pr = 26.1 μC/cm2, indicating that the structure and properties of K0.5Na0.5NbO3-based crystals grown by the seed-free solid-state crystal growth method can be closely affected by trace lithium carbonate addition.

Effect of sintering temperature on the growth of (K0.5Na0.5)NbO3 single crystals fabricated by the solid-state crystal growth method

The effect of sintering temperature on the growth of (K0.5Na0.5)NbO3 (KNN) single crystals fabricated by a solid-state crystal growth method with a sintering aid of 2 wt%Co3O4 and the seed crystals of (110) and (100) KTaO3 was investigated. For the KNN single crystals fabricated with the (110) KTaO3 seed crystal, crystal growth length was gradually increased with increasing sintering temperature at the temperatures of 1020 °C–1120 °C. At the temperatures of 1130 °C–1200 °C, rapid growth was observed and a grown single crystal reached the surfaces of the ceramic compact containing the seed crystal. The length of the KNN crystal sintered at 1140 °C for 24 h was 690 μm. On the other hand, such rapid growth was not observed for the KNN single crystals fabricated with the (100) KTaO3 seed crystal. The length of the KNN crystal sintered at 1140 °C for 24 h was 160 μm. The dielectric, ferroelectric, and piezoelectric properties of the KNN single crystal fabricated with the (110) KTaO3 seed crystal at a sintering temperature of 1140 °C were reported.

Elimination mechanism of micropores on bonding interface during solid-state crystal growth method

A pure yttrium aluminum garnet (YAG) ceramic/YAG single crystal composite material is prepared using the optimized solid-state crystal growth (SSCG) method. The micropores on the bonding interface of the composite sample are eliminated for the first time during the SSCG process and the transmittance is very close to the theoretical value, which reached 83.14% at 1064 nm. Meanwhile, the mechanism of elimination and migration of the pores under high temperature is studied. Additionally, the single crystal growth rate has significantly improved and the time of composite sample preparation has also significantly reduced proving that the SSCG method is an effective method for producing high quality composite material.

Rapid-Heating-Triggered in Situ Solid-State Transformation of Amorphous TiO2 Nanotubes into Well-Defined Anatase Nanocrystals

Fabrication of nanocrystals from their disordered solid-state precursors represents a new synthetic strategy. Compared to the widely used chemical vapor deposition and wet-chemistry based methods employing gas and liquid phased precursors, the solid-state transformation of disordered solid precursors to highly ordered crystals is a great challenge due to the severely restricted mass transport and inadequate structural directing mechanism. Herein, we report a rapid-heating-triggered in situ solid-state crystal growth method capable of transforming amorphous TiO2 nanotubes into anatase nanocrystals with well-defined facets and uniform sizes within a minute. The results obtained from in situ transmission electron microscopy and three-dimensional phase-field simulation indicate that the basic building blocks are formed through mechanical rupture of an amorphous TiO2 nanotube precursor, followed by an enhanced diffusion and concomitant oriented attachment onto TiO2 crystal nuclei mediated by the fluorine speci...