Lithium niobate(LiNbO3, LN) has a long history and variety of physical effects which can be used to make acoustic filters, resonators, delay lines, electro-optical modulators, electro-optical Q switches and phase modulator devices. It has been widely used in electronic technology, optical communication technology, laser technology, etc. Furthermore, with the rapid development of the fifth-generation wireless communication technology, micro-nano photonics, integrated photonics and quantum optics, LN crystal has important application prospects. In this paper, the basic properties, preparation and application of LN are summarized, and the future application is also analyzed.

The article summarizes the development and latest research progress of solid-state crystal growth(SSCG) technology. First of all, the phenomenon of abnormal grain growth in ceramic sintering and metallurgy process is reviewed, and the SSCG technology is also introduced. The process and application fields of the SSCG technology are introduced briefly. Some of typical application cases and development history of the SSCG technology are also described. Then, a new solid-state crystal growth technology: seed-free, solid-state crystal growth(SFSSCG) technology is introduced. The application of the SFSSCG technology in the lead-free ferroelectric and piezoelectric crystal, that is potassium sodium niobate based crystal, is introduced in detail, and the characteristics of this method are compared with the conventional high-temperature melt and SSCG method. Finally, based on the current discussion on the crystal growth mechanism of the solid-state method, a new comprehensive crystal growth mechanism is proposed for the SFSSCG method. And the current problems and future development of the SFSSCG technology are briefly described and prospected, respectively.

Microwave plasma chemical vapor deposition (MPCVD) is considered to be one of the ideal methods to synthesize large-scale and high-quality single crystal diamond. However, its low growth rate (~10 μm/h) and high defect density (103-107 cm-2) are the main factors hindering the application of MPCVD single crystal diamond. After decades of unremitting efforts of research teams, many achievements have been made in high-speed growth and high-quality growth of MPCVD single crystal diamond. But in addition to this, problem of the unity of high-speed rate and high-quality growth should be solved in order to realize the high-end application value of MPCVD single crystal diamond.

Rare-earth orthoferrite RFeO3 crystals are important multifunctional magnetic materials. Orthorhombic RFeO3 crystals display various interesting properties, like exotic magnetic behavior, excellent magneto-optical and opto-magnetic properties. The regulation of the magneto-optical and opto-magnetic properties were intensively studied in this system. In addition, orthorhombic DyFeO3 and GdFeO3 crystals exhibit magnetoelectric coupling characteristics at extremely low temperature, due to the exchange striction between R3+ and Fe3+. In recent years, novel hexagonal RFeO3 crystal has been reported to show multiferroic behavior at room temperature. The crystal growth of hexagonal RFeO3 is relatively difficult, due to its metastable state. In this paper, the crystal growth, magneto-optical, opto-magnetic and magneto-electric coupling characteristics of orthorhombic and hexagonal RFeO3 crystals are systematically reviewed, which provide valuable reference for the research of RFeO3 crystals in the future.

Piezoelectric single crystal composites (PSCCs) are important materials for preparing underwater acoustic transducers because of their high piezoelectric coefficients, electromechanical coupling factors and figure-of-merit. However, different types of underwater acoustic transducers have different requirements for piezoelectric materials, therefore, it is of great significance to design the structure and performances of PSCCs according to the specific application requirements of underwater acoustic transducers. In order to accurately select the parameters of piezoelectric phase and polymer phase, such as material properties, volume fraction, aspect ratio, et al, a design approach with a combination of analytical model and numerical model was proposed. Experimental results confirmed that this approach can accurately and efficiently predict the vibration modes and macroscopic equivalent performances of the 1-3 PSCCs. The present study provides a guideline from the underwater acoustic transducers to the PSCCs.

The research progress on rapidly grown KDP-type crystals is summarized. By integrating the pipe system of the growth equipment, upgrading the continuous filtration system, developing the real-time monitoring system of the crystal growth process and the high-precision thermal annealing equipment, the integration of the crystal growth system is realized. The flow field of crystal surface is optimized through numerical simulation, the whole process is controlled quantitatively to realize the stable crystal growth and the crystal performance is further improved through high-precision thermal annealing. In order to solve the problem of pyramid-prism boundary of “point-seed” rapidly grown KDP-type crystals, the pyramidal-restriction long-seed growth method and the free-long-seed growth method are proposed in succession, which provide new technical schemes for the growth of large size and high performance KDP-type crystals.

In order to prepare large-thickness near-stoichiometric lithium tantalate (nSLT) crystals by diffusion method, the high temperature lithium-rich diffusion process of lithium tantalate crystals were studied from the aspects of the ratio and synthesis process of Li-rich polycrystalline powders, polarization process and diffusion conditions. The lithium content, poling fields and optical homogeneity of prepared crystals were characterized, and the effect of diffusion conditions on crystal composition was studied. The results show that the repeatable use of lithium-rich polycrystalline material with Li/Ta of 60/40 has no significant effect on the composition, domain inversion voltage and optical quality of the prepared crystal wafers. Based on the research, a series of nSLT wafers were prepared. The maximum thickness of the wafer is 3.2 mm, its composition reaches the stoichiometric ratio and the composition is uniform, the coercive field is about 152 V/mm, and the crystal optical quality meets practical requirements.

Effect of La3+-doping on energy storage performance of Pb(Lu1/2Nb1/2)O3 antiferroelectric(AFE) single crystals (abbreviated as xLa-PLN, x=1%, 3%, 5%) was studied, which is abtained by the top-seed growth method. The actual components of these crystals were 0.3%, 1.1% and 2.9% by ICP test, respectively. The crystal structure is found to be perovskite orthorhombic in nature based on the XRD analysis. In addition, two superlattice reflections are identified, which stem from the antiparallel displacements of the Pb2+ and the ordered B-site ions. The dielectric spectrum shows the variation of dielectric constant, dielectric loss as a function of temperature and frequencies, and there is no diffuse phase transition. This system shows the typical double hysteresis loops and the energy storage density gradually increases with increasing La3+ content, which can reach to 5.1 J/cm3. This is mainly because La3+-doping leads to a decrease in the tolerance factor, which enhances the stability of antiferroelectric, eventually increasing the energy density of this system.

In order to explore the luminescence characteristics of Er3+ in Pb(Mg1/3Nb2/3)-PbTiO3 relaxor ferroelectric crystal field, PMN-32PT∶Er3+ relaxor ferroelectric single crystal was grown by high temperature solution method. The micro morphology, phase structure, absorption spectrum and up conversion emission spectrum of the crystal were measured and analyzed. The J-O oscillator strength parameters of Er3+ in PMN-32PT∶Er3+ crystal field were calculated by Judd Ofelt theory. The unit cell parameters of the crystals are a=0.402 3 nm, c=0.403 3 nm, V=0.065 23 nm3 and a=0.403 5 nm, b=0.403 2 nm, c=0.403 1 nm, V=0.065 57 nm3 for tetragonal and monoclinic phase respectively. The oscillator strength parameters are Ω2=1.77×10-20 cm2, Ω4=1.50×10-20 cm2, Ω6=0.79×10-20cm2, δrms=0.18×10-6. The calculated radiative lifetime of 4I11/2 is 1.75 ms. Bright green emission band (552 nm) is generate at the 980 nm excitation. The research results suggest that Er3+∶PMN-PT ferroelectric single crystal will be a new promising luminescent crystal.

In order to determine the second-order nonlinear optical property of the ultraviolet powder material, according to the Kurtz-Perry powder second-order nonlinear optical theory, a study on the second-order nonlinear optical performance test of the ultraviolet powder was carried out. The test laser is a Nd∶YAG-KTP electro-optical Q-switched laser pumped by xe-lamp. KTP is the nonlinear optical crystal, with an output wavelength of 532 nm, a single pulse energy of 100 mJ, a repetition frequency of 1-10 Hz, and a pulse width of 8 ns. In order to ensure the transmittance of 266 nm, ultraviolet melting quartz JGS1 was used as the window. In order to ensure the accuracy of the test, the grating spectrometer was selected to split the light. According to tests of KDP, LBO, BBO, which commonly used in UV prove that this method has the advantages of stability, reliability, high discrimination accuracy, and simple operation. As an important testing method, it can effectively qualitatively or semi-quantitatively test the UV second-order nonlinear optical properties of materials.

A systemic research were carried out on the problem that the lithium niobate (LN) electro-optic (EO) Q-switches have poor consistence and can not completely hold-off in pulse-off Q-switching mode. The pulse-off EO Q-switching performances of several LN Q-switches were investigated in a flash-lamp pumped Nd∶YAG laser. The possible causes for the light leakage were analyzed according to EO Q-switching theory. On these basis, the axial deviation and optical inhomogeneity were characterized by a X-ray diffraction goniometer and the conoscopic interference method. The EO inhomogeneity of LN crystals was first found, the direction of main induction axis deviated from the theoretical 45° and the induced birefringence was inconsistent throughout the clear aperture. Through contrast experiments, the EO inhomogeneity is verified to be the main reason to cause the light leakage and poor consistence.

The film bulk acoustic resonator (FBAR) has the advantages such as small volume, high operating frequency and strong performance, so that it has wide application prospects in the field of filter. The most important functional layer of FBAR filter is the piezoelectric layer composed of piezoelectric materials. In this paper, AlScN piezoelectric films were prepared on 6 inch silicon substrates by magnetron sputtering. The AlScN films were analyzed and characterized. The results show that the preferred orientations for the (002) crystal face of AlScN films are excellent, the full width at half maximum (FWHM) of the rocking curve is 1.75°. The thickness uniformity of AlScN films is less than 0.6%. The film stress is 10.63 MPa, and the stress can be adjusted. FBAR resonators based on AlScN piezoelectric films were prepared. The electromechanical coupling coefficients were 7.53%. The results show that doping Sc in AlN can improve the effective electromechanical coupling coefficient, which is significance for studying the wide band FBAR filter.

Y-orientated langatate piezoelectric crystal with size of 80 mm×100 mm was successfully grown by Czochralski method, which is transparent, inclusions-free．The relative dielectric constants and the piezoelectric strain constants were determined by an electric bridge and resonant-anti-resonant method. The performance difference between head and tail was studied. The uniformity of frequency constant has been determined to be 99.95%, which shows the excellent uniformity of the crystal. In addition, the swing curve and the temperature coefficient of frequency(TCF) were tested on (010) crystal facet. The FHMW and TCF values were 38.5″ and 1.23ppm/K, respectively.

Calcium fluoride (CaF2) crystals have high UV transmittance (>99%@193 nm) and high resistance to laser damage threshold, which have been widely used in the fields of high-power UV lasers and ArF laser lithography stepper. Stress birefringence is the key performance index of calcium fluoride in practical application, stress birefringence can cause deformation of the optical wavefront, which seriously affects image quality. Calcium fluoride crystals 210 mm in diameter were prepared by Bridgman-Stodebarger(B-S) method. The effects of crystal dislocation and small angle grain boundaries and crystal quality on stress birefringence were systematically studied. The experimental results show that the increase of dislocation density, the aggregation of small angle grain boundaries and the deterioration of crystal quality can cause the concentration of local residual stress and exacerbate the phenomenon of stress birefringence.

The hysteresis loop equation of PbZr0.4Ti0.6O3/SrTiO3 hetero-junction was constructed by the modified Landau-Devonshire thermody-namic model, and the analytical functions of remanent polarization intensity Pr, coercive electric field Ec and effective energy storage density Wrecwith respect to the thin film thickness h of PbZr0.4Ti0.6O3 were obtained, respectively, and then the effects of the thickness of the PbZr0.4Ti0.6O3 thin films on ferroelectric properties and ferroelectric energy storage properties were investigated. The results show that Pr, Ec and Wrec all increase nonlinearly with the increase of PbZr0.4Ti0.6O3 film thickness h, and reach saturation values of 75.3 μC·cm-2, 2 240.7 kV·cm-1 and 9.0 J·cm-3 when the thickness h is 57.0 nm, 64.2 nm and 65.8 nm, respectively, the energy storage conversion efficiency η, however, decreases nonlinearly with the increase of h, reaching a stable value of 4.79% when h is close to 52.6 nm. In addition, both W′rec(h) and η′(h), the instantaneous relative rates of change, decrease with the increase of h, when h is less than 2.4 nm, η′(h) is greater than W′rec(h), when h is greater than 2.4 nm, η′(h) is less than W′rec(h), and η′(h)/W′rec(h) tends to a stable value of 0.65 as h is close to 50.0 nm.

In order to quickly and accurately measure the fracture toughness of brittle cleavable gallium oxide crystals, to provide a theoretical basis for the precise processing of gallium oxide. A G200 nanoindenter was used to perform a nanoindentation test on gallium oxide crystals. The indentation morphology was analyzed by a scanning electron microscope. The indentation method and the energy method were used to calculate fracture toughness. The fracture toughness of the (010) plane gallium oxide crystal was 0.769 MPa·m1/2, and the fracture toughness of the (010) plane was 0.782 MPa·m1/2. Compared with the traditional fracture toughness testing method, the indentation method and energy method based on nanoindenter can quickly test the fracture toughness of brittle materials with micro damage. Energy method is a more accurate and convenient method for testing nano-scale fracture toughness.

The gadolinium-based borate Rb2LiGdB2O6 (RLGBO) single crystals were obtained by the spontaneous crystallization method from the Rb2CO3-Li2CO3-Gd2O3-H3BO3 system. Meanwhile, the polycrystalline powder RLGBO were obtained by solid phase reaction. The analysis of single crystal structure shows that RLGBO belongs to the orthorhombic system, Pbcm space group, with cell parameters of a=7.025 9(3), b=9.610 3(4), c=10.056 2(4) and z=4. Thermal properties indicate that RLGBO is stable below 840 ℃. After 2% Ce3+, 80% Eu3+ and 50% Tb3+ are doped in the RLGBO respectively, the host structure remains unchange. Under ultraviolet (UV) or near-UV light excitation, RLGBO∶Ce3+, RLGBO∶Eu3+ and RLGBO∶Tb3+can emit blue, red and green lights, respectively. The results show that RLGBO is a promising matrix compound for luminescence materials.

The locally resonant (LR) cylindrical shell phononic crystal structure with periodically attached spring-mass resonators in the circumferential direction of cylindrical shells is proposed in this study to reduce the vibration of cylindrical shells. And the band structure of the phononic crystal shows that the two low frequency band gaps can be formed. One of the band gaps has a starting frequency as low as 650 Hz and a bandwidth of 330 Hz, and the other has a lower frequency range of 0 to 371 Hz, which is due to the coupling between the cylindrical shell and spring-mass resonators. Further, the effects of the mass ratio of the cylindrical shell to the mass, the stiffness of the spring-mass resonators and the cell width on the band gaps were analyzed. Moreover, the characteristics of the vibration transmission in finite LR cylindrical shells verify the vibration suppression in the band gap for the locally resonant cylindrical shell phononic crystal. Finally, the research results provide a theoretical reference for the vibration reduction of cylindrical shells.

Existence of bandgap is an important characteristic of the periodic materials or structures, which has potential use in the development of vibration/sound isolation and frequency filters. By controlling and adjusting the material layout and properties in the periodic microstructure, phonon crystals with special bandgap requirements were designed. In this paper, the optimal design of one-dimensional three-phase phnononic crystals were investigated by genetic algorithm and topology optimization technique and two examples were presented. The results show that three-phase materials can achieve better vibration isolation effect and will reduce the bandgap frequency greatly compared with the two-phase materials, even get up to 99.21% forbidden band. Therefore, it is feasible to use evolutionary algorithm to optimize and design the topology of multi-phase phononic crystals.

Solvent refining is one of the processing methods for production of solar-grade silicon. During Al-Si solvent refining process, the cooling rate has a significant effect on microstructure and purity of primary silicon. In this paper, the Al-30wt%Si melt was solidified at different cooling rates, then the microstructures and impurity contents were analyzed. The results show that the length and width of primary silicon increase with the cooling rate decrease, which results in the increase of recovery rate of primary silicon. The -orientation was preferred in the lower cooling rate range during growth of primary silicon grains. Meanwhile, it is obvious that the impurity content is related to the cooling rate. In the lower cooling rate range, the removal rate of impurities is higher, especially for the B and Ti impurities. Accordingly, to improve the recovery rate and purity of primary Si in the refining process of Al-30wt%Si alloy, the cooling rate of molten solvent should be lower than 3 ℃/min.

In view of the lack of effective and timely online testing methods for the current quality effects of ingot products, this paper proposes an on-line detection system for the production gas of polycrystalline silicon ingots. The system realizes the online automatic sampling real-time analysis and the function of over-limit alarm, which can be based on real-time automatic sampling and real-time analysis through dry pump sampling, pressurization test, and real-time analysis of the argon gas, which is an exhaust of the technical exhaust gas in the process of ingot production. Changes in the atmosphere in the furnace cavity during the production process, early detection of faults and abnormalities in the ingot furnace reduced the yield of abnormal products. Through the support of the follow-up battery data, the limit values of water leakage and gas leakage of the equipment can be determined to achieve the effect of fine-tuning the quality of silicon ingots and early warning of danger, and prepare for the pre-research for the ingot argon gas recovery system.

This paper presents a detailed study of gap-filling method to fabricate graphene films with high quality on polished Cu substrate. The nucleation density of graphene domains (GDs) reduces on the electrochemically and mechanically polished (ECMP) Cu substrate. Through the optical microscope and scanning electron microscope (SEM) testing of the graphene domains grown on the unpolished and polished Cu substrate, it demonstrated that the surface morphology of the Cu substrate was crucial in reducing the nucleation density and increasing the size of GDs. The Raman maps demonstrate that the GDs were homogeneous and monolayer graphene domains. Then large-area homogeneous monolayer graphene films with large-scale hexagonal domains were synthesized on the polishing Cu substrate by the gap-filling method. The process of preparing high quality graphene film by gap-filling method is explained through flow chart. Consequently, the technique of fabricate graphene films with high quality on polished Cu substrate by gap-filling method proposed in this paper can conveniently improve the properties of graphene films and graphene-based photoelectronic devices.

The MoS2/graphene composites were prepared by hydrothermal method. Then the composites were fabricated to gas sensors for exploring the sensing characteristics of mercury vapor. When the molar ratio of graphene and MoS2 was 0.5%, the composites has the best gas sensor response. The concentration in 2.18-126.18 mg/m3 of mercury vapor was tested, and the sensor show excellent linearity. When the concentration of mercury vapor is 29.48 mg/m3, the response time of the sensor is 8.5 min and the recovery time is 9.0 min. The sensor has excellent repeatability, stability and selectivity. Other common gases in coal-fired power plant flue gas such as H2S, NH3 and NO2 has no obvious response, and the sensor can be used for practical detection.

The stability, electronic structure and optical properties of ZnO with Cu/Ag doped and Cu-Ag codoped were studied by first-principles method. Formation energies of CuZn2 and CuZn1-CuZn3 are close to 0.0 eV, and negative for CuZn1-CuZn2, which indicates that Cu doped is effortless and tends to gather. The value for AgZn2 is 2.5 eV, and higher than 4.5 eV for AgZn1-AgZn2 and AgZn1-AgZn3. It’s difficult for Ag doping with higher concentration. Formation energies of CuZn1-AgZn2 and CuZn1-AgZn3 are close to that of AgZn2. The Cu3d and O2p states have obvious hybridization in models of CuZn2, CuZn1-CuZn2 and CuZn1-CuZn3, the top of valence band is mainly occupied by Cu3d states. The hybridization between Ag4d and O2p states for AgZn2, AgZn1-AgZn2 and AgZn1-AgZn3 models is weaker, the top of valence band is mainly occupied by O2p states. For CuZn1-AgZn2 and CuZn1-AgZn3 models, although Cu3d states hybridize with O2p states, the top of valence band is mainly occupied by O2p states. Cu/Ag doped and Cu-Ag codoped lead Zn4s states downward significantly, which reduces the band gap of above models. They influence the electronic structure of ZnO near the band gap mainly. The modified ability of Cu-Ag codoped to ZnO electronic structure is between Cu/Ag doped ZnO. The absorption edges of above models have obvious red-shift, which realizes the visible light absorption for ZnO. The ultraviolet light absorption also is higher than pure ZnO in the range of 3.10-3.90 eV. Cu/Ag doped and Cu-Ag codoped improves the photocatalytic activity of ZnO. According to formation energy analysis, the models with higher photocatalysis under different doping are CuZn1-CuZn2, AgZn2 and CuZn1-AgZn2.

In this paper, a series of m-SCCN composite photocatalytic materials were prepared by direct calcination using strontium carbonate (SrCO3) and melamine (C3H6N6) as raw materials. The photocatalytic degradation effect of m-SCCN composites prepared by different raw material ratios, different calcination temperatures and different calcination time on crystal violet solution under visible light was studied. The materials were characterized by SEM, XRD, UV-Vis and so on. The results show that the treatment effect of crystal violet is best when SrCO3∶C3H6N6 is 7%(w/w), calcination temperature is 600 ℃, and calcination time is 4 h. The removal rate can reach 89.70% after 120 min of light, which is 5 times that of pure g-C3N4 (17.70%). The analysis mechanism may be that SrCO3 destroys part of the hydrogen bonds in the g-C3N4 plane, resulting in the ring opening of the hepazine unit to generate a strong electron-withdrawing group-cyano group (-C≡N), which changs the transmission path of photogenerated electrons. The separation efficiency of photogenerated electrons and holes optimizes the photocatalytic activity of m-SCCN.

Anatase TiO2 spheres with algae spherical shape were synthesized using Na salt and K salt by normal pressure hydrolysis-ion exchange method. The surface of the material is covered with ultra-fine nano-TiO2 whiskers, forming three-dimensional, interconnected, nanopore anatase structure. The crystal structure and morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and the electrochemical performance of lithium storage was tested. The material exhibits excellent electrochemical performance. At a current density of 100 mA · g-1, the first specific discharge capacities of samples synthesized from Na salt and K salt methods are 347 mAh·g-1 and 242 mAh·g-1, respectively. The TiO2 sample prepared by Na salt has better rate performance, it has a high specific capacity of 168 mAh·g-1 at a current density of 2 000 mA · g-1, and shows good cycling performance, it still remains at 153 mAh·g-1 after 20 cycles.

Nanocrystalline powder of gadolinium-doped-ceria (Gd0.2Ce0.8O1.9, GDC) was successfully synthesized by one step, low cost and environment friendly maillard method, using glucose as organic solvent and urea as addictives. The synthesized GDC powders were analyzed by a range of techniques including TG/DSC, XRD, Raman spectroscopies, FESEM, in-situ XRD and electrochemical impedance. The results reveal that the synthesized powder has a single cubic fluorite structure and forms pure-phase nanoparticles with adjustable size, narrow particle size distribution, and high crystallinity in the range of 10-50 nm. After sintering at 1 550 ℃, the dense GDC electrolyte pellets with an average grain size of 3 μm and small number of grain boundaries is obtained which is pre-sintered at 800 ℃. They have superior electrochemical performance and structural stability. The test results above prove that Maillard method is suitable for the synthesis of GDC.