Lithium Tantalate Niobate Single Crystals Research Articles

Piezoelectric and ferroelectric properties of lead-free niobium-rich potassium lithium tantalate niobate single crystals

Lead-free potassium lithium tantalate niobate single crystals with the composition of K0.95Li0.05Ta1−xNbxO3 (abbreviated as KLTN, x=0.51, 0.60, 0.69, 0.78) were grown using the top-seeded melt growth method. Their piezoelectric and ferroelectric properties in as-grown crystals have been systematically investigated. The phase transitions and Curie temperatures were determined from dielectric and pyroelectric measurements. Piezoelectric coefficients and electromechanical coupling factors in thickness mode, length-extensional mode and longitudinal mode were obtained. The piezoelectric properties are very attractive, e.g. for x=0.60 composition, kt≈70%, k31≈70%, k33≈77%, d31≈230pC/N, d33≈600pC/N are comparable to the lead-based PZT composition. The polarization versus electric field hysteresis loops show saturated shapes. In short, lead-free niobium-rich KLTN system possesses comparable properties to those in important lead-based piezoelectric material nowadays.

Growth, characterization and upconversion properties of erbium-doped potassium lithium tantalate niobate single crystals under 975 nm laser excitation

Potassium lithium tantalate niobate single crystals doped with erbium ions are grown by top-seeded solution growth method. The crystals are characterized by X-ray diffraction and differential thermal analysis. The refractive indices of the crystal are measured using ellipsometry method and fitted by Sellmeier equation. The as-grown crystals are tetragonal phase tungsten bronze-type structure with Curie temperature of 271.3°C. Characteristic Er3+ absorption bands are observed from 350 to 1100nm in ultraviolet–visible-near infrared absorption spectra. These crystals emit brightly green and red upconversion fluorescence under 975nm LD laser excitation, and the steady state upconversion spectra are obtained at room temperature. The red emission intensity increases as the erbium ions concentration increases in crystals. Processes of excited state absorption and energy transfer are responsible for upconversion luminescence. The emission intensities are quadratic dependences on pump power from pump power dependence analyses and deduction of transition rate equation model.

Spectroscopic and upconversion properties of Er 3+/Yb 3+-codoped KLTN single crystal

A high optical quality erbium and ytterbium codoped potassium lithium tantalate niobate single crystal is grown by top-seed solution growth method, and the crystal structure is confirmed to be 4 mm point group and P4/ mbm space group by powder X-ray diffraction analysis. The ultraviolet–visible–near infrared absorption spectrum, upconversion fluorescence spectrum excited by 975 nm continuous wave laser, power dependence, and fluorescence decay curves of Er 3+ ions in the crystal are measured at room temperature. The Judd–Ofelt (JO) intensity parameters are calculated using the JO theory and absorption spectrum. The relationship of JO parameters Ω 4 < Ω 6 of Er 3+ in the crystal is different from the general trend of Ω 2 > Ω 4 > Ω 6. The absorption cross sections and emission cross sections of H 11 / 2 2 , S 3 / 2 4 , and F 9 / 2 4 levels are calculated. The upconversion mechanism of Er 3+ in the crystal is discussed based on pump power dependence analyses and decay curves. The emission intensities exhibit quadratic behaviors against pump energy, which are verified by the deduction of transition rate equation model.

Electric-field-controlled two-dimensional Raman–Nath diffraction from paraelectric potassium lithium tantalate niobate

Electric-field-controlled two-dimensional Raman–Nath diffraction has been realized using a photorefractive diffraction grating. The grating was produced by two-wave coupling (at a wavelength of 632.8 nm) at small incidence angles using a potassium lithium tantalate niobate single crystal. Results for the Raman–Nath diffraction from the g 44 grating are presented, in which the externally applied field is perpendicular to both the grating vector and the wave vector of the incident beam. Two pairs of coherent beams were used to record the grating for two-dimensional Raman–Nath diffraction. The wave vector and the polarization of one pair lay in the ( x, z) plane, and those of the other pair lay in the ( y, z) plane. The influence of the applied electric field was studied, and the results show that the intensity of the Raman–Nath diffraction could be controlled by the direction and intensity of the applied field.

Electric field control of a Bragg diffraction optical beam splitter based on a cubic K_099Li_001Ta_063Nb_037O_3 single crystal

We have realized an electric field controlled Bragg diffraction optical beam splitter based on a photorefractive Bragg diffraction grating. In our experiments, the splitter was produced by wave coupling (532.0 nm) with a potassium lithium tantalate niobate single crystal. In the process of splitting, the incident beam could be split into multioutput beams by the splitter. The influence of an externally applied electric field was studied, and the results show that the intensity of the Bragg diffraction could be controlled by the electric field. The polarization properties of the splitter are discussed.

Electric field control of a two-dimensional higher order diffraction optical beam splitter based on a cubic K0.99Li0.01Ta0.63Nb0.37O3 single crystal

An electric field controlled two-dimensional higher order diffraction optical beam splitter has been realized based on a photorefractive higher order diffraction grating. In experiments, the splitter was produced by wave coupling (632.8 nm, 532.0 nm) at a small incident angle with a potassium lithium tantalate niobate single crystal. In the process of splitting, the incident beam of different wavelengths (632.8 nm, 532.0 nm) could be split into multi-output beams by the splitter. The influence of an externally applied electric field was studied and results show that the intensity of higher order diffraction could be controlled by the electric field. The polarization properties of higher order diffraction were discussed. An electric field controlled five–three optical beam splitter was investigated theoretically.

Piezoelectric properties of the lead-free K0.95Li0.05Ta0.61Nb0.39O3 single crystal

Lead-free potassium lithium tantalate niobate single crystal with the composition of K0.95Li0.05Ta0.61Nb0.39O3 has been grown by the top-seeded solution growth method. The dielectric and piezoelectric properties of the as-grown crystal have been investigated. From the experimental results, the orthorhombic–tetragonal and tetragonal–cubic phase transition temperatures of this single crystal are −72 °C and 15 °C, respectively. It exhibits good piezoelectric properties, namely the electromechanical coupling factor k31 reaches 40.4%, the piezoelectric constant d33 reaches 431 pC N−1 and d31 reaches 183.1 pC N−1. These excellent properties indicate that K0.95Li0.05Ta0.61Nb0.39O3 single crystal is a very promising lead-free piezoelectric material for designing applicable devices and transducers.