Properties Of LiNbO3 Single Crystals Research Articles

Depth profiling of dopant concentration and pyroelectric properties of LiNbO3 single crystals treated at high-temperature in the presence of metal ions

The dopant and pyroelectric coefficient depth profiles of LiNbO3 single crystals grown by Czochralski method were investigated. Doping was performed after crystal growth by thermal diffusion at elevated temperatures. Diffusion doping did not deteriorate the pyroelectric properties of the crystal.

Effect of Zn doping on the photoluminescence properties of LiNbO3 single crystals

An extraordinary violet luminescence at 418 nm together with the intrinsic blue band at 440 nm with excitation in the UV region (380 nm) was observed in a series of LiNbO3 single crystals doped with Zn. Structural and photoluminescence properties were studied by Raman, UV reflectance, and fluorospectrometry, respectively. The emission peaks in PL spectra varied in amplitude according to the level of concentration of Zn in LiNbO3 crystals. It was found, from Raman spectroscopy studies, a connection between the appearance of the new emission band centered at 418 nm and a diminishing in the Li concentration in crystals, which suggest the displacement of the Li ions from their regular sites by the Zn ions. The maximum peak intensity of each one of the three PL emission components found from a deconvolution process shows a linear dependence on the Zn concentration present in the crystals studied.

Influence of gamma and gamma-neutron irradiation on the optical properties of LiNbO3 single crystals

The influence of radiation effects (gamma and mixed gamma-neutron irradiation) on the refractive indices and optical inhomogeneity of lithium niobate single crystals of congruent composition is investigated. The temperature dependences of the optical characteristics of the irradiated crystals exhibit a number of anomalies in the temperature range 20–400°C.

The crystallization and optical properties of LiNbO3 single crystals

LiNbO3 single crystals were grown by the Czochralski technique in an air atmosphere. The critical crystal diameter Dc = 1.5 cm and the critical rate of rotation wc = 35 rpm were calculated from the dynamic of fluids equations for buoyancy-driven and forced convections under which the shape of the melt/crystal interface changed. The domain inversion was carried out at 1473 K using a 10 min 3.75 V/cm electric field. The obtained crystals were cut, polished and etched to determine the presence of dislocations and single domain structures. The lattice parameters a = 0.51494 nm, c = 1.38620 nm and V = 0.3186 nm 3 were determined by X-ray powder diffraction. The optical properties were studied by infrared spectroscopy in the wave number range 20. 5000 cm -1. With decreasing temperature, an atypical behaviour of the phonon modes, due to the ferroelectric properties of LiNbO3 single crystal, could be seen. The optical constants were calculated by Kramers-Kronig analysis and the value of the critical temperature was estimated. The obtained results are discussed and compared with published data.

The optical properties of LiNbO3 single crystals obtained in air atmosphere

Single crystals of LiNbO3 were grown by the Czochralski technique in an air atmosphere. The critical diameter and the critical rate of rotation were calculated. X-Ray measurements of the powder were carried out to obtain the lattice parameters.The optical constants were calculated by Kramers-Kronig analysis of reflectance data. The optical properties of LiNbO3 single crystals were studied for samples grown in an air atmosphere to investigate the influence of air on the optical properties of the formed crystals. A peak due to OH. gtroups appears in the transmission spectrum at 3385 cm -1. It was still present after annealing in an air atmosphere at temperature up to 873 K, but it was no longer detectable after annealing at 1473 K in an electric field. Thick films of the high-temperature superconductor YBa2Cu3O7 (Ag) were obtained on plates of LiNbO3 single crystals. The obtained results are discussed and compared with published data.

The silicon impurity as a possible growth‐regime indicator for LiNbO3 crystals

AbstractThe influence of Si concentration and temperature regimes on the visually observable properties of LiNbO3 single crystals grown by Czochralski method was studied. Si concentration measurements were carried out and minima in the radial and axial distribution curves have been established. An upper estimate is given for the equilibrium distribution coefficient of Si in LiNbO3. A direct correlation has been found between the degree of opacity and the Si concentration. The variation of the Grashof number during growth and a correlated modification of the structure of the concentration layer width, implying a position dependent fulfilment of the Hurle‐Bardsley criterium for constitutional supercooling, accounts reasonably well with the visually observable properties of the opaque regions appearing in the course of crystal growth. The use of Si as an overall indicator for the characterization of growth regimes is discussed.

Growth, stoichiometry and properties of LiNbO3 single crystals

LiNbO3 single crystals were grown from melt by Czochralski method, for acousto-electronic purposes. The stoichiometric problems in connection with growing were studied by chemical methods: gravimetric method, based on the determination of Nb in its NbO(Oxine)3 complex; volumetric method, involving titration of peroxo-niobium(V) complex; spectrophotometric determination, in form of peroxo-niobium(V) complex in its acidic solution at 340 nm. The properties of crystals were investigated by physical methods. The inclusions, strains were studied by different microscopic investigations.