Narrow Results

The influence of different concentrations of Mg²⁺ ions doping on the structure, morphology and phase transition of LiIO₃ crystal was investigated. The best Mg²⁺-doped alpha-lithium iodate (Mg:α-LiIO₃) crystals for potential optical applications can be successfully grown by the aqueous solution method when the concentration of Mg²⁺ ions in the initial mother solutions C_m< 0.001 M. Chemical component analysis shows the Mg:α-LiIO₃ crystal is a new system with the segregation coefficient k>1. The polarized Raman results are consistent with our conclusions that the Mg²⁺ ion substitutes for the host Li⁺ cation in the pure α-LiIO₃ crystals and results in the corresponding cation vacancies. As C_m increases, inclusions, spontaneously crystalline grains, β phase of LiIO₃ and hillock-shape Mg:α-LiIO₃ crystals are induced respectively by different concentrations of Mg²⁺ ions doping under the same crystal growth conditions. When C_m>0.1 M, the polarized Raman results indicate that larger amounts of Mg²⁺ ions incorporated inhibit LiIO₃ growth and result in the hillock-shape morphology by destabilizing the crystal lattice and inducing lattice distortion.

A series of ${\mathrm{\text{In:Yb:Nd:LiNbO}}}_3$ crystals with various [Li]/[Nb] ratios (0.946, 1.05, 1.20 and 1.38) were grown by the Czochralski method. They were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES). As the [Li]/[Nb] ratio increases in the melt, the segregation coefficients of ${\mathrm{\text{Yb}}}^{3+}$ and ${\mathrm{\text{Nd}}}^{3+}$ ions increase, while the segregation coefficient of ${\mathrm{\text{In}}}^{3+}$ ions decrease. The [Li]/[Nb] ratio in the crystal of sample ${\mathrm{\text{LN}}}_{1.20}$ is 0.996, which is near stoichiometric. The dopant occupancy with different [Li]/[Nb] ratios was analyzed by IR transmission spectrum and UV-VIS-NIR spectrum. When the [Li]/[Nb] ratio reaches 1.20, the absorption peak at $3505{\mathrm{\text{cm}}}^{-1}$ indicates that the threshold concentration of ${\mathrm{\text{In}}}^{3+}$ is 1 mol.% in the sample ${\mathrm{\text{LN}}}_{1.20}$.

Lithium niobate is a crystal with excellent electric-optic and nonlinear optical properties. Double-doped and multi-doped lithium niobate are widely used in a wide variety of optical devices. A series of Zn:Ru:Fe:LiNbO₃ crystals with different lithium-niobium molar ([Li]/[Nb]) ratios were grown by the Czochralski method. The structures of the crystals with different [Li]/[Nb] ratios are analyzed using X-ray diffraction patterns and infrared spectra. The effect of the [Li]/[Nb] ratio dependence of the doped element concentration and segregation coefficient was studied using an inductive coupled plasma-atomic emission spectrometer (ICP-AES). It was found that the doping elements do not change the crystal structure, and the change of the [Li]/[Nb] ratio will affect the concentration and the occupancy of the doped ions in the crystal. The segregation coefficient and defect structures can be controlled by different [Li]/[Nb] ratios in Zn:Ru:Fe:LiNbO₃ crystal.

Mg:Fe:Cu:LiNbO₃ crystals with different [Li]/[Nb] ratios (0.946, 1.05, 1.20, 1.38) were prepared by the Czochralski method. The crystal structure and the occupancy of impurity ions were analyzed by X-ray diffraction (XRD). The effective segregation coefficient was analyzed by an inductively coupled plasma-atomic emission spectrometer (ICP-AES). The optical uniformity of the crystal is analyzed by birefringence gradient. The results show that the dopant ions do not change the crystal structure, and the concentration of dopant ions changes with the ratio of [Li]/[Nb]. The greater the ratio of [Li]/[Nb], the better the optical uniformity. Finally,we conclude that when the [Li]/[Nb] ratio approaches 1.20, the intrinsic defects of Mg:Fe:Cu:LiNbO₃ crystals almost disappear and the crystals approach the stoichiometric ratio. When the [Li]/[Nb] ratio is 1.38, the optical uniformity of the crystal is the best.

Zn:Yb:Tm:LiNbO₃ crystals with a range of [Li]/[Nb] ratios (0.94, 1.05, 1.20, and 1.38) were grown by Czochraski technique. The influence of [Li]/[Nb] ratio on the concentration of doped elements in grown crystal was investigated by inductively coupled plasma atomic emission spectrometry (ICP-AES). The defect structures formed at different [Li]/[Nb] ratios were studied by X-ray diffraction and INFRARED spectroscopy. The results show that, when the [Li]/[Nb] ratio increases, the segregation coefficients of ${\text{Yb}}^{3+}$ and ${\text{Tm}}^{3+}$ ions increase, while the segregation coefficient of ${\text{Zn}}^{2+}$ ions decreases. When the [Li]/[Nb] ratio in the melt increases to 1.20, the Zn:Yb:Tm:LiNbO₃ crystal approaches the stoichiometric ratio.

The 0.96Na_0.5Bi_0.5TiO₃–0.04K_0.5Bi_0.5TiO₃ (NKBT96/4) lead-free single crystal was successfully grown by top-seeded solution growth method. The effective segregation coefficient for K was calculated to be 0.20. X-ray powder diffraction measurement showed that the as-grown crystal possesses rhombohedral perovskite structure at room temperature. X-ray rock curve measure indicated that the as-grown single crystal owned relatively higher quality. The NKBT96/4 single crystal exhibits apparent diffused dielectric behavior, where the diffusiveness index α is 1.79 for the [001]-oriented crystal planes. A notable thermal hysteresis, ΔT_h, of 25°C was disclosed for the tetragonal antiferroelectric-tetragonal paraelectric phase transition in the dielectric property studies between heating and cooling. The highest remnant polarization, P_r, 16.8 μC/cm², was obtained at 100°C. The electromechanical coupling coefficient k_t of the [001]-oriented crystal planes at room temperature was determined to be 38% using resonance–antiresonance technique. The room temperature piezoelectric constant d₃₃ reaches 120 pC/N.