Y. G. Liu

Growth and characterization of cubic KTa1-xNbxO3 crystals

Abstract The top-seeded flux method was used to grow large size and good quality undoped, Cu or Fe doped cubic phase KTa 1- x Nb x O 3 crystals. The morphology, homogeneity, dielectric properties and electrooptic properties of these crystals have been investigated. The photorefractive properties of a Cu-doped KTN crystal have also been studied and the results obtained show that the diffraction efficiency of this crystal is above 50% at room temperature.

Soft-Mode Spectroscopy in Fe:KTa1-xNbxO3 Crystals

Fe-doped potassium tantalite niobate, Fe:KTa 1-x Nb x O 3 (Fe:KTN), crystallizes with x = 0.48 and a perovskite-type structure in tetragonal system with point group 4mm, conforming space group P4mm. The paraelectric-ferroelectric structural transition of the Fe:KTN is studied by Raman scattering investigations. A condensed soft lattice vibrational mode at the phase transition has been analyzed. It originates from the symmetric O2/O3-Nb/Ta-O3/O2 in-plane bending of the Nb/TaO 6 group. The soft optical phonon mode concerns the extraordinary transverse optical phonons propagating along the [110] direction. The Raman spectra measured reflect the crystal disorder. Curie temperature measured by two methods is within 353 and 3 56.5 K.

Characterization of Growth Defects in Nd:YCa4O(BO3)3 Crystals by Transmission Synchrotron Topography

The growth defects in Nd: YCa 4 O(BO 3 ) 3 (Nd: YCOB) crystals were investigated by transmission synchrotron topography. It was found that growth striations were the primary defects in Nd:YCOB crystals. Grown-in dislocations, mosaic blocks and inclusions were also observed in the crystals. The effect of temperature field on the formation of growth defects in the crystals was discussed.

LaAl2.03(B4O10)O0.54

The title compound, lanthanum aluminium borate, has been found to be isostructural with hexagonal NdAl 2.07 (B 4 O 10 )O 0.6 . Each La ion is coordinated by six O atoms to form a trigonal prism, while each Al is coordinated by five O atoms to form a pyramid.

Self-frequency doubled green NdxY1-xCa4O(BO3)3 laser

Nd-doped yttrium calcium oxyborate, Nd x Y 1-x Ca 4 O(BO 3 ) 3 (NYCOB), was grown using pulling from the melt, with large sizes and good optical quality as well as different Nd 3+ -ion densities of 0 to 10 at% in the lattice structure. These crystals belong to the monoclinic system with point group m, conforming space group C m . The unit cell constants were a = 0.8076(7), b = 1.6020(10), and c = 0.3527(2) nm for a Nd 3+ content of 8 at%, with β = 101.23°, and z = 2. The measured absorption of the NYCOB was compared to Judd-Ofelt (JO) theory. When applied, the JO theory of parity-forbidden electric-dipole transitions of rare earth ions on non-centrosymmetric sites demonstrates good agreement. The polarized absorption coefficients at 811 nm were calculated as α X = 1.59, ay = 1.75, and α Z = 2.02 1/cm, respectively. The valence-conduction band gap is about 5.39 eV. The fitted intensity parameters Ω t (t = 2, 4, and 6) were 3.51×10 -20 , 7.82×10 -20 , and 3.79×10 -20 cm 2 , with a root-mean square deviation of 6.30 x 10 -21 cm 2 . The emission properties of the excited 4 F 3/2 state with the level lifetime of 216.67 μs were studied, which exhibit the two pass bands of laser for possible applications in practice. The self-frequency doubling tests are interesting. A very low threshold power of 2 mW for a sample with average Nd 3+ content of 7 at%, length of 6 mm, and phase matching angles of 0 = 64.5° and φ = 35.5° have been measured. The measured output power of green light was 19.4 mW accompanied with a conversion efficiency of 3.7%.

Growth defects in flux grown RbTiOAsO4 crystals observed with white-beam synchrotron radiation topography

Abstract The growth defects in flux grown RbTiOAsO 4 crystal have been investigated by white-beam synchrotron radiation topography. It is found that growth sector boundaries are the primary growth defects and they show strong X-ray kinematical contrast in the topograph. All the dislocations are growth induced and appear only in the near capping region. The area away from the capping region is nearly dislocation free. Growth bands show weak contrast in the X-ray topograph, which implies that the impurity contents are relatively low in various growth sectors and each growth sector is uniform in composition.

The thermal properties of KTa1−xNbxO3 crystal

Abstract The thermal properties such as phase transition heat, specific heat and linear expansion of KTN (x=0.37) crystal have been measured within the temperature range of 130-370 K. The experimental results have been discussed briefly.

The DC Conductive Property of KTiOPO4 Crystal along its Z-Axis

The anomalous DC electrical conductive property of the KTP crystal along its z-axis is reported in this paper. The DC conductivity strongly depends on the measurin oltage. No Ohmic regime exists in the current-voltage relation. Ionic polarization occurs under high DC stresses. Electrode reactions were also observed. The phenomena are related to the easy movement of ions along the z-axis of the KTP crystal.

Study on the relationships of mechanical performance with the short-range and long-range structure of 500–900℃ carbonized fiber

The relationships of mechanical performance with the short-range and long-range structure of 500–900℃ carbonized fibers were studied by the combination of radial distribution function (RDF), Fourier transform infrared spectroscopy (FT-IR) and high-resolution transmission electron microscopy (HRTEM), etc. In the range of 500–900℃, there were different laws of change for tensile strength and elastic modulus during different temperature stages. The tensile strength was more nearly directly proportional to temperature, especially at higher than 600℃. The elastic modulus increased slowly from 500 to 700℃, and then elastic modulus increased rapidly after 700℃. The short-range structures had no effects on the mechanical performance. The uniform increasing rate of tensile strength was closely related to the crystallinity degree and crystal size. The outstanding increase of orientation degree was closely related to the change of elastic modulus.

Crystal growth and ferroelectric properties of KTa1−xNbxO3:Cu

Abstract The Cu-doped KTa1−xNbxO3 (KTN) crystals have been grown by flux pulling method. The ferroelectric properties of this crystal has been studied and its phase transition features have been revealed by the measurements of dielectric constant, dielectric loss, spontaneous polarization and pyroelectric coefficient in temperature range of -140° ∼ + 100°C.