Properties Of LiNbO3 Research Articles

The Fabrication of Lithium Niobate Nanostructures by Solvothermal Method for Photocatalysis Applications: A Comparative Study of the Effects of Solvents on Nanoparticle Properties

In this work, we report, for the first time, a comparative study on the effects of different solvents on the properties of LiNbO3 (LN) nanostructures. The solvothermal synthesis method was successfully used with three different solvents: 1—water, 2—methanol, and 3—benzyl. The structural and optical properties of the as-prepared nanoparticles were studied using transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-Vis absorbance, Raman spectroscopy, and photoluminescence (PL). Nanoparticles of a very small size, with an average size between 3 and 10 nm, were obtained for the first time. The photocatalytic activities of the three synthesized LiNbO3 nanoparticles were studied in relation to the photodegradation of a complex and heavy reactive black 5 dye for a wastewater treatment application. The LiNbO3 synthesized with deionized water showed a higher photocatalytic activity than those synthesized using other solvents, such as methanol or benzyl.

Enhanced dielectrics, ferroelectric and optical properties of lithium niobate for high temperature applications using potassium oxide (K2O) additive

Dielectrics, Ferroelectric and Optical properties of Lithium Niobate has been examined using Potassium Oxide (K2O) as an additive on the samples prepared by solid state reaction method using high energy ball milling. The crystal structure analysis by Rietveld structure refinement confirms that the LiNbO3 (LN) with K2O additive also exhibit the rhombohedral structure with R3c space group. The SEM characterization of the microstructure reveals that the samples sintered at a temperature of 1050 °C, have regular and uniform grain morphology and better density. The average grain size decreases for the K2O added compositions in the beginning and increases later for higher concentration of additive. Thermal study with TGA suggests that as the activation energy is decreases, the polarization is enhanced and the LN composition with 2.72 wt% K2O additive shows the best thermal stability. The frequency and temperature dependent dielectric properties were investigated in a wide range of frequency and a substantial enhancement in the dielectric constant of LN is obtained by K2O addition. A useful enhancement in permittivity is obtained with increase of temperature. The band gap values for direct and indirect band gaps for the various compositions are also determined. The least direct band gap is discovered to be 2.36 eV for the composition with 2.72 wt% K2O additive. The composition-dependent photoluminescence (PL) emission studies reveal that the emission spectra for both the pure LiNbO3 and K2O added LiNbO3 compositions lies in the UV–visible region. All the investigated compositions exhibit distinct green, yellow, and red emission peaks. The LN with 2.72 wt% K2O additive shows the best dielectric, thermal stability and polarization response with maximum polarization Ps ∼1.16 μC/cm2. The present investigations suggest that properties of LN can be significantly improved by using K2O additive for sustainable, low cost, environmental friendly energy storage material for high temperature applications.

Strain engineering for tuning the electronic and optical properties of lithium niobate for optoelectronic applications

In this paper, the first-principles calculations are presented to examine the effect of strain on the electronic and optical properties of Lithium niobate (LiNbO3). Recent advancements in the use of strain engineering for tuning the properties of the materials advocate investigating the effect of strain on the properties of LiNbO3. In this work, the influence of the strain of varying intensities of 10% and 20% (tensile and compressive) is investigated on the electronic and optical response of LiNbO3. The LiNbO3 is a wide bandgap material with a bandgap of 3.56 eV, which can be narrowed down by the application of strain. On the application of a tensile strain of 10%, the bandgap is reduced to 2.54 eV, which is further reduced to 1.71 eV for the tensile strain of 20%. The optical absorption which was in the ultra-violate region for unstrained structure is significantly shifted in the visible region for the applied tensile strain of 10% and 20% (Redshift). For the compressive strain, the bandgap is increased and the absorption is found more in the UV region (Blueshift). The high absorption in the visible region due to the application of tensile strain makes the strained LiNbO3 a potential candidate for optoelectronic applications.

Effect of the Doped Growth Charge Preparation Process on the Growth Conditions and Properties of LiNbO3:B:Mg Single Crystals

Effect of the Doped Growth Charge Preparation Process on the Growth Conditions and Properties of LiNbO3:B:Mg Single Crystals

Дефекты и некоторые физические свойства номинально чистых и легированных цинком кристаллов ниобата лития

The features of defect structure and their influence on the properties of LiNbO3:Zn crystals, doped in a wide concentration range, including two concentration thresholds (at ~ 3.0 and ~ 6.8 mol. % ZnO in the melt), were studied by absorption IR spectroscopy in the region of OH--group valence vibrations, photoluminescence in the visible region of the spectrum, and photoinduced light scattering. In LiNbO3:Zn(0.004-2.01 mol. % ZnO) crystals the increase of zinc concentration led to increasing in the OH--group concentration and decreasing the luminescence intensity of luminescence centers associated with NbLi defects. Apparently, the latter was connected with the formation of small energy levels near the bottom of the conduction band as the zinc atoms displaced niobium atoms from the lithium positions in the ideal structure and the NbLi defect concentration decreased, respectively. In highly doped LiNbO3:Zn crystals (4.46-6.5 mol. % ZnO) and in the LiNbO3stoich(6.0 wt. % K2O) crystal there were lower OH--group concentration, the increase of band gap by 0.3-0.4 eV, and the increase of luminescence intensity in the green region of the spectrum due to the formation of new recombination channels compared to weakly doped crystals. In addition, in such crystals, the increase of proton conductivity was observed due to increasing in the concentration of interstitial hydrogen H+ and, as a result, the formation of many small acceptor levels near the valence band.

Influence of a Static Electric Field on the Dielectric Properties of LiNbO3

Influence of a Static Electric Field on the Dielectric Properties of LiNbO3

Effect of external pressure on the structural stability, electronic structure, band gap engineering and optical properties of LiNbO3: An ab-initio calculation

A detailed theoretical investigation to explore the effects of external pressure (0.0GPa, 2.5GPa, 5.0GPa, 7.5GPa, 10GPa, 12.5GPa, 15GPa, 17.5GPa, 20GPa and 25GPa) on structural stability, electronic structure, band gap engineering and its impact on optical properties in LiNbO3 by using CASTEP code, based on ab-initio density functional theory, with ultra-soft pseudopotential and exchange correlation functional GGA-PBE, is presented. From band structure, it is observed that the top of the valence band is typically controlled by O-2p and Nb-4d orbital electrons and the band gap exhibits nearly linear decreasing trend (3.542eV–2.905eV) with the increasing external pressure. Decreasing trend of the electronic band gap with increase of external pressure is explained with the help of total density of states and elemental partial density of states. Moreover, with the increase of external pressure beyond 25 GPa stability of the structure degrades significantly. In addition, to study the impact of band gap reduction on the optical properties, we have also calculated the refractive index, the reflectivity, absorption function and the energy loss function of the LiNbO3 by the complex dielectric function under various external pressures. The optical results reveal that the static refractive index increases with the increase of pressure and the variation ranges of the absorption function and the reflectivity rate are also broadened. Absorption spectra, under increase of pressure, show the red shift and the major plasmon peaks display blue shift, which is the thumb proof of electronic band gap reduction. Both the electronic structures and optical properties of LiNbO3 can be constructively tempered with pressure, which contributes an effective theoretical basis for the further application of the LiNbO3 under pressure.

Defect Complexes and Optical Properties of Doubly Doped Lithium Niobate Crystals

The effect of defect complexes related to the presence of protons on the optical properties of LiNbO3:Y(0.24):Mg(0.63) and LiNbO3:Gd(0.25):Mg(0.75) (wt %) crystals has been studied using IR absorption spectroscopy, photoinduced light scattering, and laser conoscopy. The results indicate that the absorption bands at frequencies of 3483 and 3486 cm–1 correspond to vibrations of a V Li - –OH− defect complex. To a Mg Li + - Mg Nb 3- –OH−defect complex in the LiNbO3:Gd(0.25):Mg(0.75) crystal correspond bands at frequencies of 3526 and 3535 cm–1. In the LiNbO3:Y(0.24):Mg(0.63) crystal, we have detected an anomalous opening of the speckle structure of the photoinduced light scattering indicatrix.

Photorefractive Properties of Molybdenum and Hafnium Co-Doped LiNbO3 Crystals

A series of LiNbO3: Mo, Hf crystals with 0.5 mol % fixed MoO3 and various HfO2 concentrations (0.0, 2.0, and 3.5 mol %) were grown by the Czochralski technique. The photorefractive properties of the LiNbO3: Mo, Hf crystals were investigated by two-wave coupling measurements and the beam distortion method was employed to obtain the optical damage resistance ability. The UV-visible and OH− absorption spectra were also studied. The experimental results imply that the photorefractive properties of LiNbO3: Mo crystals at laser wavelengths of 532, 488, and 442 nm can be greatly enhanced by doping HfO2 over the threshold concentration. At 442 nm especially, the response time of LN: Mo, Hf3.5 can be shortened to 0.9 s with a diffraction efficiency of 46.07% and a photorefractive sensitivity reaching 6.28 cm/J. Besides this, the optical damage resistance at 532 nm is 3 orders of magnitude higher than that of the mono-doped LiNbO3: Mo crystal, which is beneficial for applying it in the field of high-intensity lasers.

Spectroscopic Properties of LiNbO3:Tm3+ Crystal in the 1650–1970 nm Wavelength Range

Taking into account the Stark structure of optical spectrum of the impurity ion, the theoretical study of spectroscopic properties of LiNbO3:Tm3+ crystal in the wavelength range of 1650–1970 nm was carried out. The wave functions of the Stark sublevels of both ground 3H6 and the first excited 3F4 manifolds of the Tm3+ ion were constructed in the LSJM-representation, the line strengths induced by indirect electric-dipole transitions were calculated, and the main spectroscopic characteristics of emission and absorption spectra of impurity ion were determined.

Structure and Properties of Boron-Doped LiNbO3 Single Crystals

We have studied the macro-and microstructure and properties of LiNbO3〈B〉 crystals in comparison with LiNbO3〈Zn〉 and stoichiometric and congruent lithium niobate crystals. The optical characteristics of the LiNbO3〈B〉 crystals have been shown to approach those of the stoichiometric LiNbO3 and LiNbO3〈Zn〉 crystals.

Effect of charge mixture preparation technology on the physicochemical and optical properties of LiNbO3:Mg crystals

LiNbO3:MgO crystals, representing important materials for nonlinear optics, laser optics, integrated optics, and optical electronics owing to their high resistance with respect to optical damage, are studied. The crystals of LiNbO3:MgO were grown from a granulated charge mixture of lithium niobate synthesized using homogeneously doped Nb2O5:Mg precursors of different origin. The effect of organic substances used in the technology of lithium niobate charge mixture on the properties of LiNbO3:MgO single crystals is studied. It is found that the physicochemical and optical characteristics of LiNbO3:MgO crystals grown from charge mixtures synthesized from Nb2O5:Mg precursors obtained using organic solvents and without them differ to a considerable extent. It is suggested that the difference in the properties of LiNbO3:MgО crystals of different origin is caused by change in the structure of the ion complexes in the melt owing to the presence of traces of organic impurities. Change in the structure of ion complexes in the melt leads to change in crystallization mechanisms and, accordingly, in the chemical composition and the properties of LiNbO3:MgO crystals. Furthermore, it is shown that the use of homogeneous doping methods as opposed to the method of direct doping provides the distribution coefficient K eef > 1. That is, the method of homogeneous doping allows one to introduce a substantially greater concentration of an impurity element in the LiNbO3:MgO crystal compared with the direct method for doping the charge mixture at the same impurity concentration in the starting material.

Photorefractive properties of congruent lithium niobate crystals doped with zinc

Optical and structural homogeneity and photorefractive properties of LiNbO3:Zn crystals (0.03 to 4.5 mol % Zn) were investigated by the methods of laser conoscopy, photoinduced light scattering, and Raman spectroscopy. It is established that the photorefractive effect nonmonotonically depends on the concentration of Zn2+ and is almost absent in LiNbO3:Zn crystals containing 0.05 and 4.5 mol % Zn. The suppression of photorefraction is explained by a decrease in the number of defects with the electrons localized on them due to the replacement of the NbLi and VLi defects by Zn2+ cations, by the appearance of shallow traps near the bottom of the conduction zone, and by the radiative recombination of laser-induced photo-electrons. The conoscopic pattern of a single-axis crystal of high optical quality was observed in a LiNbO3:Zn crystal containing 4.5 mol % Zn upon irradiation by the laser with a power of 90 mW. This pattern is of much better quality than the one observed with a laser radiation power of 1 mW, which is explained by curing of the defects by the laser radiation. An area of highly ordered structure with high alternation ordering of main and doped cations and vacancies along the polar axis in the cation sublattice is detected.

Synthesis of homogeneously mg-doped lithium niobate batch and study of the effect of non-metal impurities on the properties of LiNbO3:Mg crystals

The preparation conditions for the homogeneously doped precursor Nb2O5:Mg for the synthesis of granulated lithium niobate batch was studied. The effect of non-metallic impurities in the Nb2O5:Mg precursors and the lithium niobate batch on the characteristics of the melt–crystal system and the physicochemical and optical characteristics of the LiNbO3:Mg crystals was established.

First-principles study on the electronic structures and optical properties of Cu, Fe doped LiNbO_3 crystals

The binding energies, electronic structures and optical properties of LiNbO3 and Cu/Fe doped LiNbO3 crystals are investigated by first principles based on the density functional theory in this paper. The supersell structures of crystals are established each with 60 atoms, including five models: pure LiNbO3, LN1 (Cu2+ occupy Li+ site), LN2 (Fe3+ occupy Li+ site), LN3 (Cu2+ occupy Li+site and Fe3+ occupy Li+ site) and LN4 (Cu2+ occupy Li+ site and Fe3+ occupy Nb5+ site). The optimized results show that the total energies of all models can achieve certain stable values, which means that the models accord with the actual crystal structures. The impurity energy levels of Cu and Fe doped LiNbO3 crystals appear within the band gaps, which are contributed by Cu 3d orbital, Fe 3d orbital and O 2p orbital; in co-doped LiNbO3, Cu offers deep energy level and Fe offers shallow energy level within the band gaps. There are two wide absorption peaks appearing respectively at 445 nm and 630 nm in co-doped LiNbO3 crystal, which correspond to the electron transitions from Eg orbital of Cu to Nb 4d orbital and T2g orbital of Fe to Nb 4d orbital respectively; the absorption edge of Cu, Fe mono and co-doped LiNbO3 crystals are red-shift successively, which coincides with the variation of band gape. The light absorption intensity of co-doped LiNbO3 crystal is stronger than that of mono-doped LiNbO3 crystal. The co-doped sample light absorption property is related to Fe site occupation. In this paper, it is suggested that the co-doped sample with Fe at Nb site is more competitive than that with Fe at Li site in optical volume holographic storage applications, and that reducing properly [Fe2+]/[Fe3+] value may be conducible to the formation of this advantage.

Study of spectroscopic properties of LiNbO3:Ho3+ crystal in 1880–2130 nm luminescence band

Theoretical study of spectroscopic properties of LiNbO3:Ho3+ crystal in the wavelength range of 1880–2130 nm was carried out, when the Stark structure of optical spectrum of the impurity ion was taken into account. Wave functions of Stark sublevels of the ground (5 I 8) and first excited (5 I 7) multiplets of the Ho3+ ion were defined, the line strengths induced by the indirect electric-dipole and magnetic-dipole intra-Stark transitions were calculated, and the main spectroscopic characteristics were determined on this basis.

Optical Tuning of Dielectric Properties of LiNbO3:Mg in the Terahertz Range

Tuning of the dielectric permittivity spectra of congruent LiNbO3:Mg single crystals in an external optical pump is investigated at room temperature by means of terahertz time-domain spectroscopy. Application of the optical pump leads to an appreciable tuning of the permittivity, which reaches up to 2.3%. We find that the change of refractive index has a linear relationship on scale with the applied light power. These findings are attributed to the internal space charge field of photorefraction caused by the excited free carriers.

Electrical properties of LiNbO3〈RE〉 crystals grown under steady-state and transient conditions

The static piezoelectric and dielectric properties and electrical conductivity of LiNbO3〈RE〉 crystals grown under steady-state and transient conditions have been studied in the temperature range ∼290–490 K and in a wide frequency range. The magnitude of the observed anomalies in the electrical characteristics of the crystals and the kinetics of the underlying processes are determined by the micro- and nanodomain structures of the samples.

Structure and properties of LiNbO3 doped Bi(Mg1/2Ti1/2)O3–PbTiO3 ceramics with the morphotropic phase boundary composition

(1−x){0.62Bi(Mg1/2Ti1/2)O3–0.38PbTiO3}–xLiNbO3 (BMT–0.38PT–xLN, 0.00 ≤ x ≤ 0.06) ceramics were prepared by the conventional mixed oxide method. It showed that all compositions belong to the pseudocubic phase when LN doped into BMT–0.38PT ceramics, meanwhile piezoelectric properties declined. With LN content increasing, a change from a ferroelectric behavior to an abnormal diffuse behavior was observed. Furthermore, stable dielectric permittivity (1,300–3,800) and low losses were obtained in the temperature range 100–400 °C for 0.02 ≤ x ≤ 0.06 samples, indicating a potential for high-temperature applications.

Properties of LiNbO3Thin Film Deposited by Chemical Vapor Deposition and Frequency Characteristics of Film Bulk Acoustic Wave Resonator

Properties of LiNbO₃Thin Film Deposited by Chemical Vapor Deposition and Frequency Characteristics of Film Bulk Acoustic Wave Resonator