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10 pages, 10705 KiB

Open AccessArticle

Super-Lattice Structure and Phase Evolution of Pb(Lu_0.5Nb_0.5)O₃-PbTiO₃ Single Crystal with Low PbTiO₃

by Ying Liu, Xiaoming Yang, Chao He, Xiuzhi Li, Zujian Wang and Xifa Long

Crystals 2018, 8(2), 50; https://doi.org/10.3390/cryst8020050 - 23 Jan 2018

Cited by 4 | Viewed by 4630

Abstract

The phase diagram of the Pb(Lu_0.5Nb_0.5)O₃-PbTiO₃ (PLN-PT) binary system was previously reported based on XRD and dielectric measurements results. Unusually, the Curie temperature of PLN-PT with low PT obtained from the phase diagram is much lower [...] Read more.

The phase diagram of the Pb(Lu_0.5Nb_0.5)O₃-PbTiO₃ (PLN-PT) binary system was previously reported based on XRD and dielectric measurements results. Unusually, the Curie temperature of PLN-PT with low PT obtained from the phase diagram is much lower than that of PLN and PT end members, which is different from others, such as PZT. Therefore, the complex structure of PLN-PT with low PT is desired to be studied. In this work, PLN-PT single crystals with low PT were grown for the study of their super-lattice structure and phase evolution. The super-lattice reflections were identified by X-ray diffraction. Domains and their evolution by heating from room temperature to 150 °C were observed under a polarized light microscope. The phase transition from the ferroelectric phase to the paraelectric phase was determined by dielectric spectra and polarized light microscopy. A precursor/intermediate phase exhibiting pinched hysteresis loops was displayed above the Curie temperature, which originates from some polar region embedded in the non-polar matrix. The coexistence of the ferroelectric and antiferroelectric domains leads to peculiarities of the phase transitions, such as a lower Curie temperature compared with PLN and PT. The studies of the phase evolution of PLN-PT with low PT single crystal is a supplementary amendment of the PLN-PT phase diagram as previously reported. Full article

(This article belongs to the Special Issue Crystal Growth for Optoelectronic and Piezoelectric Applications)

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10 pages, 5314 KiB

Open AccessArticle

Temperature Dependence of the Thermal, Electrical Resistivity, Dielectric and Piezoelectric Properties of CaYAl₃O₇ Crystal

by Yang Li, Zhitai Jia, Yanru Yin, Qiangqiang Hu, Wenxiang Mu, Jian Zhang, Xiaoqiang Yu and Xutang Tao

Crystals 2018, 8(1), 34; https://doi.org/10.3390/cryst8010034 - 17 Jan 2018

Cited by 9 | Viewed by 4892

Abstract

Calcium yttrium aluminate (CaYAl₃O₇) crystal was grown and characterized in detail for high temperature piezoelectric sensors for the first time. The thermal properties of the CaYAl₃O₇ (CYAM) crystal were investigated systematically. In particular, the CYAM crystal [...] Read more.

Calcium yttrium aluminate (CaYAl₃O₇) crystal was grown and characterized in detail for high temperature piezoelectric sensors for the first time. The thermal properties of the CaYAl₃O₇ (CYAM) crystal were investigated systematically. In particular, the CYAM crystal exhibits considerably high resistivity along X- and Z- direction in the order of 6.96 × 10⁷ Ω·cm and 2.86 × 10⁸ Ω·cm at 600 °C, respectively. The temperature dependence of the electromechanical properties of CYAM crystal were investigated over the temperature range of 25–500 °C. The high thermal stability of piezoelectric properties together with its high electrical resistivity, makes CaYAl₃O₇ crystal a promising candidate for high temperature piezoelectric applications. Full article

(This article belongs to the Special Issue Crystal Growth for Optoelectronic and Piezoelectric Applications)

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12 pages, 2261 KiB

Open AccessArticle

Modeling and Analysis of Novel Horizontal Ribbon Growth of Silicon Crystal

by Jiawei Xu, Dapeng Shen, Tao Sun, Jianning Ding and Ningyi Yuan

Crystals 2018, 8(1), 36; https://doi.org/10.3390/cryst8010036 - 16 Jan 2018

Cited by 2 | Viewed by 3879

Abstract

We present a novel horizontal ribbon growth (HRG) process and a theoretical analysis of this method. Assuming that the existence of the meniscus is defined by diffuse growth, we determine analytically the thickness and height of the meniscus and an explicit expression for [...] Read more.

We present a novel horizontal ribbon growth (HRG) process and a theoretical analysis of this method. Assuming that the existence of the meniscus is defined by diffuse growth, we determine analytically the thickness and height of the meniscus and an explicit expression for the performance of meniscus under different conditions. We then calculate the thermal profile in melt part, as well as the conditions under which the undercooling is sufficient around the solidification point. We find that diffuse growth is more sensitive to small initial thickness, and find the minimum length of the melt part to obtain undercooling. Finally, we calculate the change rule of solidification position by a variational approach, as well as the stability of the process under different conditions. We also give an expression to the instability of past HRG methods. Full article

(This article belongs to the Special Issue Crystal Growth for Optoelectronic and Piezoelectric Applications)

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2936 KiB

Open AccessArticle

Pb(In_1/2Nb_1/2)O₃–Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ Piezoelectric Single-Crystal Rectangular Beams: Mode-Coupling Effect and Its Application to Ultrasonic Array Transducers

by Wei Wang, Siu Wing Or and Haosu Luo

Crystals 2017, 7(4), 101; https://doi.org/10.3390/cryst7040101 - 2 Apr 2017

Cited by 4 | Viewed by 4873

Abstract

Pb(In_1/2Nb_1/2)O₃–Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ (PIN–PMN–PT) piezoelectric single-crystal rectangular beams with the PIN:PMN:PT ratio of 0.33:0.35:0.32 are prepared, and their mode-coupling effect is investigated both theoretically and experimentally for ultrasonic array transducer applications. The [...] Read more.

Pb(In_1/2Nb_1/2)O₃–Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ (PIN–PMN–PT) piezoelectric single-crystal rectangular beams with the PIN:PMN:PT ratio of 0.33:0.35:0.32 are prepared, and their mode-coupling effect is investigated both theoretically and experimentally for ultrasonic array transducer applications. The PIN–PMN–PT rectangular beams become a tall-narrow beam and a short-wide plate, and so exhibiting an uncoupled height-extensional (beam) mode and an uncoupled thickness-extensional (plate) mode, at a width-to-height ratio G (= L / H) of <0.7 and >6.0, respectively. With G varying in the range of 1.6 to 3.1, the beam mode not only couples strongly with the width (lateral) mode, but also coexists obviously with the plate mode, giving high electromechanical coupling coefficients k_33^' and k_t of ~0.75 and ~0.50, respectively. With the guide of the mode-coupling results, a multifrequency ultrasonic array transducer having three distinct operational frequencies of 1.52, 2.60, and 6.01 MHz, corresponding to the coupled/coexistent beam mode, lateral mode, and plate mode, respectively, is developed using a mode-coupled rectangular beam of G = 1.6. Two different single-frequency ultrasonic array transducers, fabricated using two different uncoupled rectangular beams, one operating in uncoupled beam mode with G = 0.6 at 2.24 MHz and one working in uncoupled plate mode with G = 10.0 at 5.75 MHz, are also developed for comparison. Full article

(This article belongs to the Special Issue Crystal Growth for Optoelectronic and Piezoelectric Applications)

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16878 KiB

Open AccessArticle

Growth and Physical Properties of Sr_xCa_1−xCrO₃ Single Crystals

by Lipeng Cao, Aizi Jin, Changzhi Gu, Haiyang Bai, Youwen Long, Richeng Yu, Liqing Pan and Changqing Jin

Crystals 2017, 7(3), 91; https://doi.org/10.3390/cryst7030091 - 21 Mar 2017

Viewed by 5054

Abstract

Perovskites Sr_xCa_1−xCrO₃ attract much attention due to the controversy on the anomalous electronic state. In this study, we synthesized a series of Sr_xCa_1−xCrO₃ (0 ≤ x ≤ 1) single crystals under high pressure [...] Read more.

Perovskites Sr_xCa_1−xCrO₃ attract much attention due to the controversy on the anomalous electronic state. In this study, we synthesized a series of Sr_xCa_1−xCrO₃ (0 ≤ x ≤ 1) single crystals under high pressure and high temperature conditions with self-oxidization. The crystal structure was determined using X-ray diffraction (XRD). With the increase of x, the structure transformed from orthorhombic to tetragonal to cubic. Antiferromagnetism was observed except for SrCrO₃, and the T_N decreased with increased x. All samples demonstrated semiconductive behavior by electrical resistivity measurement. Full article

(This article belongs to the Special Issue Crystal Growth for Optoelectronic and Piezoelectric Applications)

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1729 KiB

Open AccessArticle

Crystal Growth and Glass-Like Thermal Conductivity of Ca₃RE₂(BO₃)₄ (RE = Y, Gd, Nd) Single Crystals

by L. V. Gudzenko, M. B. Kosmyna, A. N. Shekhovtsov, W. Paszkowicz, A. Sulich, J. Z. Domagała, P. A. Popov and S. A. Skrobov

Crystals 2017, 7(3), 88; https://doi.org/10.3390/cryst7030088 - 17 Mar 2017

Cited by 14 | Viewed by 5310

Abstract

Crystal growth and thermal properties of binary borates, Ca₃RE₂(BO₃)₄ (RE = Y, Gd, Nd), are considered promising crystals for laser applications. These single crystals were grown by the Czochralski method. The crystal and defect structure were [...] Read more.

Crystal growth and thermal properties of binary borates, Ca₃RE₂(BO₃)₄ (RE = Y, Gd, Nd), are considered promising crystals for laser applications. These single crystals were grown by the Czochralski method. The crystal and defect structure were characterized. Volumetric chemical methods without prior separation of the components were developed and applied for the determination of the dependence of chemical compositions of the crystals on the growth conditions. The thermal conductivity was investigated in the 50–300 K range. The character of the temperature dependence of thermal conductivity was found to be similar to that of glass. The possible reasons of the observed features of the thermal conductivity were analyzed. Full article

(This article belongs to the Special Issue Crystal Growth for Optoelectronic and Piezoelectric Applications)

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5186 KiB

Open AccessArticle

The Effect of Trimethylaluminum Flow Rate on the Structure and Optical Properties of AlInGaN Quaternary Epilayers

by Dongbo Wang, Gang Liu, Shujie Jiao, Lingping Kong, Teren Liu, Tong Liu, Jinzhong Wang, Fengyun Guo, Chunyang Luan and Zhenghao Li

Crystals 2017, 7(3), 69; https://doi.org/10.3390/cryst7030069 - 6 Mar 2017

Cited by 4 | Viewed by 4775

Abstract

In this work, a series of quaternary Al_xIn_yGa_1−x−yN thin films have been successfully achieved using metal organic chemical vapor deposition (MOCVD) method with adjustable trimethylaluminum (TMA) flows. Surface morphology and optical properties of Al_xIn_y [...] Read more.

In this work, a series of quaternary Al_xIn_yGa_1−x−yN thin films have been successfully achieved using metal organic chemical vapor deposition (MOCVD) method with adjustable trimethylaluminum (TMA) flows. Surface morphology and optical properties of Al_xIn_yGa_1−x−yN films have been evaluated. The indium segregation effect on the enhancement of UV luminescence emission in Al_xIn_yGa_1-x-yN films with increasing TMA flows was investigated. Our results shed some lights on future optical materials design and LED/LD applications. Full article

(This article belongs to the Special Issue Crystal Growth for Optoelectronic and Piezoelectric Applications)

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4410 KiB

Open AccessArticle

A Novel Effect of CO₂ Laser Induced Piezoelectricity in Ag₂Ga₂SiS₆ Chalcogenide Crystals

by Oleg V. Parasyuk, Galyna L. Myronchuk, Anatolij O. Fedorchuk, Ahmed M. El-Naggar, Abdullah Albassam, Andrii S. Krymus and Iwan V. Kityk

Crystals 2016, 6(9), 107; https://doi.org/10.3390/cryst6090107 - 31 Aug 2016

Cited by 6 | Viewed by 4322

Abstract

We have discovered a substantial enhancement of the piezoelectric coefficients (from 10 to 78 pm/V) in the chalcogenide Ag₂Ga₂SiS₆ single crystals. The piezoelectric studies were done under the influence of a CO₂ laser (wavelength 10.6 μm, time [...] Read more.

We have discovered a substantial enhancement of the piezoelectric coefficients (from 10 to 78 pm/V) in the chalcogenide Ag₂Ga₂SiS₆ single crystals. The piezoelectric studies were done under the influence of a CO₂ laser (wavelength 10.6 μm, time duration 200 ns, lasers with power densities varying up to 700 MW/cm²). Contrary to the earlier studies where the photoinduced piezoelectricity was done under the influence of the near IR lasers, the effect is higher by at least one order, which is a consequence of the phonon anharmonic contributions and photopolarizations. Such a discovery allows one to build infrared piezotronic devices, which may be used for the production of the IR laser tunable optoelectronic triggers and memories. This is additionally confirmed by the fact that analogous photoillumination by the near IR laser (Nd:YAG (1064 nm) and Er:glass laser (1540 nm)) gives the obtained values of the effective piezoelectricity at of least one order less. The effect is completely reversible with a relaxation time up to several milliseconds. In order to clarify the role of free carriers, additional studies of photoelectrical spectra were done. Full article

(This article belongs to the Special Issue Crystal Growth for Optoelectronic and Piezoelectric Applications)

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Review

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35 pages, 19400 KiB

Open AccessReview

Enhancing Light Extraction of Inorganic Scintillators Using Photonic Crystals

by Matteo Salomoni, Rosalinde Pots, Etiennette Auffray and Paul Lecoq

Crystals 2018, 8(2), 78; https://doi.org/10.3390/cryst8020078 - 1 Feb 2018

Cited by 50 | Viewed by 10830

Abstract

Inorganic scintillators are commonly used as sensors for ionizing radiation detectors in a variety of applications, ranging from particle and nuclear physics detectors, medical imaging, nuclear installations radiation control, homeland security, well oil logging and a number of industrial non-destructive investigations. For all [...] Read more.

Inorganic scintillators are commonly used as sensors for ionizing radiation detectors in a variety of applications, ranging from particle and nuclear physics detectors, medical imaging, nuclear installations radiation control, homeland security, well oil logging and a number of industrial non-destructive investigations. For all these applications, the scintillation light produced by the energy deposited in the scintillator allows the determination of the position, the energy and the time of the event. However, the performance of these detectors is often limited by the amount of light collected on the photodetector. A major limitation comes from the fact that inorganic scintillators are generally characterized by a high refractive index, as a consequence of the required high density to provide the necessary stopping power for ionizing radiation. The index mismatch between the crystal and the surrounding medium (air or optical grease) strongly limits the light extraction efficiency because of total internal reflection (TIR), increasing the travel path and the absorption probability through multiple bouncings of the photons in the crystal. Photonic crystals can overcome this problem and produce a controllable index matching between the crystal and the output medium through an interface made of a thin nano-structured layer of optically-transparent high index material. This review presents a summary of the works aiming at improving the light collection efficiency of scintillators using photonic crystals since this idea was introduced 10 years ago. Full article

(This article belongs to the Special Issue Crystal Growth for Optoelectronic and Piezoelectric Applications)

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21 pages, 7665 KiB

Open AccessReview

Rare-Earth Tantalates and Niobates Single Crystals: Promising Scintillators and Laser Materials

by Renqin Dou, Qingli Zhang, Jinyun Gao, Yuanzhi Chen, Shoujun Ding, Fang Peng, Wenpeng Liu and Dunlu Sun

Crystals 2018, 8(2), 55; https://doi.org/10.3390/cryst8020055 - 24 Jan 2018

Cited by 31 | Viewed by 5807

Abstract

Rare-earth tantalates, with high density and monoclinic structure, and niobates with monoclinic structure have been paid great attention as potential optical materials. In the last decade, we focused on the crystal growth technology of rare-earth tantalates and niobates and studied their luminescence and [...] Read more.

Rare-earth tantalates, with high density and monoclinic structure, and niobates with monoclinic structure have been paid great attention as potential optical materials. In the last decade, we focused on the crystal growth technology of rare-earth tantalates and niobates and studied their luminescence and physical properties. A series of rare-earth tantalates and niobates crystals have been grown by the Czochralski method successfully. In this work, we summarize the research results on the crystal growth, scintillation, and laser properties of them, including the absorption and emission spectra, spectral parameters, energy levels structure, and so on. Most of the tantalates and niobates exhibit excellent luminescent properties, rich physical properties, and good chemical stability, indicating that they are potential outstanding scintillators and laser materials. Full article

(This article belongs to the Special Issue Crystal Growth for Optoelectronic and Piezoelectric Applications)

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19 pages, 4639 KiB

Open AccessReview

Characterization of Pb-Free KNbO₃- and (Na,Bi)TiO₃-Based Piezoelectric Single-Crystals Using X-ray and Neutron Diffraction

by Abhijit Pramanick

Crystals 2018, 8(2), 49; https://doi.org/10.3390/cryst8020049 - 23 Jan 2018

Cited by 1 | Viewed by 5100

Abstract

In view of serious environmental concerns with traditional Pb-based piezoelectrics, the search for new Pb-free alternatives has intensified recently. A thorough investigation of structure-property relationships in Pb-free piezoelectrics is desired in order to design new material compositions with high electromechanical properties that can [...] Read more.

In view of serious environmental concerns with traditional Pb-based piezoelectrics, the search for new Pb-free alternatives has intensified recently. A thorough investigation of structure-property relationships in Pb-free piezoelectrics is desired in order to design new material compositions with high electromechanical properties that can be operated over a broader range of conditions. Recent availability of high-quality single crystals has not only opened the possibility for achieving multifold enhancements in the electromechanical properties in this new class of materials, but has also provided opportunities to undertake fundamental studies on their structure-property relationships. In the following pages, I review some of the recent X-ray and neutron diffraction studies of Pb-free piezoelectric single crystals, which have provided novel insights into their multiscale stimuli-induced structural mechanisms, including phase transitions, nanoscale structural ordering, lattice instability, and domain re-orientation. Opportunities and challenges for future progress in this area of study are discussed. Full article

(This article belongs to the Special Issue Crystal Growth for Optoelectronic and Piezoelectric Applications)

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967 KiB

Open AccessReview

Hydrothermal Crystal Growth of Piezoelectric α-Quartz Phase of AO₂ (A = Ge, Si) and MXO₄ (M = Al, Ga, Fe and X = P, As): A Historical Overview

by Olivier Cambon and Julien Haines

Crystals 2017, 7(2), 38; https://doi.org/10.3390/cryst7020038 - 4 Feb 2017

Cited by 11 | Viewed by 7980

Abstract

Quartz is the most frequently used piezoelectric material. Single crystals are industrially grown by the hydrothermal route under super-critical conditions (150 MPa-623 K). This paper is an overview of the hydrothermal crystal growth of the AO₂ and MXO₄ α-quartz [...] Read more.

Quartz is the most frequently used piezoelectric material. Single crystals are industrially grown by the hydrothermal route under super-critical conditions (150 MPa-623 K). This paper is an overview of the hydrothermal crystal growth of the AO₂ and MXO₄ α-quartz isotypes. All of the studies on the crystal growth of this family of materials enable some general and schematic conclusions to be made concerning the influence of different parameters for growing these α-quartz-type materials with different chemical compositions. The solubility of the material is the main parameter, which governs both thermodynamic parameters, P and T, of the crystal growth. Then, depending on the chemistry of the α-quartz-type phase, different parameters have to be considered with the aim of obtaining the basic building units (BBU) of the crystals in solution responsible for the growth of the α-quartz-type phase. A schematic method is proposed, based on the main parameter governing the crystal growth of the α-quartz phase. All of the crystal growth processes have been classified according to four routes: classical, solute-induced, seed-induced and solvent-induced crystal growth. Full article

(This article belongs to the Special Issue Crystal Growth for Optoelectronic and Piezoelectric Applications)

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10516 KiB

Open AccessReview

Control of Intrinsic Defects in Lithium Niobate Single Crystal for Optoelectronic Applications

by Rajeev Bhatt, Indranil Bhaumik, Sarveswaran Ganesamoorthy, Riscob Bright, Mohammad Soharab, Ashwani Kumar Karnal and Pradeep Kumar Gupta

Crystals 2017, 7(2), 23; https://doi.org/10.3390/cryst7020023 - 24 Jan 2017

Cited by 46 | Viewed by 8602

Abstract

A single crystal of lithium niobate is an important optoelectronic material. It can be grown from direct melt only in a lithium deficient non-stoichiometric form as its stoichiometric composition exhibits incongruent melting. As a result it contains a number of intrinsic point defects [...] Read more.

A single crystal of lithium niobate is an important optoelectronic material. It can be grown from direct melt only in a lithium deficient non-stoichiometric form as its stoichiometric composition exhibits incongruent melting. As a result it contains a number of intrinsic point defects such as Li-vacancies, Nb antisites, oxygen vacancies, as well as different types of polarons and bipolarons. All these defects adversely influence its optical and ferroelectric properties and pose a deterrent to the effective use of this material. Hence, controlling the defects in lithium niobate has been an exciting topic of research and development over the years. In this article we discuss the different methods of controlling the intrinsic defects in lithium niobate and a comparison of the effect of these methods on the crystalline quality, stoichiometry, optical absorption in the UV-vis region, electronic band-gap, and refractive index. Full article

(This article belongs to the Special Issue Crystal Growth for Optoelectronic and Piezoelectric Applications)

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2978 KiB

Open AccessReview

Advances in Single-Crystal Fibers and Thin Rods Grown by Laser Heated Pedestal Growth

by Gisele Maxwell, Bennett Ponting, Eminet Gebremichael and Ruben Magana

Crystals 2017, 7(1), 12; https://doi.org/10.3390/cryst7010012 - 4 Jan 2017

Cited by 22 | Viewed by 7467

Abstract

Single-crystal fibers are an intermediate between laser crystals and doped glass fibers. They have the advantages of both guiding laser light and matching the efficiencies found in bulk crystals, which is making them ideal candidates for high-power laser and fiber laser applications. This [...] Read more.

Single-crystal fibers are an intermediate between laser crystals and doped glass fibers. They have the advantages of both guiding laser light and matching the efficiencies found in bulk crystals, which is making them ideal candidates for high-power laser and fiber laser applications. This work focuses on the growth of a flexible fiber with a core of dopant (Er, Nd, Yb, etc.) and a polycrystalline clad of yttrium aluminum garnet (YAG) that will exhibit good wave guiding properties. Direct growth or a combination of growth and cladding experiments are described. Scattering loss measurements at visible wavelengths, along with dopant profile characterization with damage threshold results, are also presented. For single-pass amplification, a single-pass linear gain of 7.4 was obtained for 29 nJ pulses of 5 ns duration at 1 MHz repetition rate. We also obtained a laser efficiency of over 58% in a diode-pumped configuration. These results confirm the potential for single-crystal fibers to overcome the limitations of the glass fibers commonly used in fiber lasers, making them prime candidates for high-power compact fiber lasers and amplifiers. Full article

(This article belongs to the Special Issue Crystal Growth for Optoelectronic and Piezoelectric Applications)

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