Papers by Keyword: LiTaO₃

Abstract: Lithium tantalate (LT) is a kind of excellent pyroelectric materials that can be made into high performance pyroelectric detector. As the detector voltage response and detection rate inversely proportional to the thickness of the infrared sensing element, So the thinning of lithium tantalate crystals becomes a key of success. This design uses CMP method to produce 50 μm thickness of LT wafer, and via charge integration method with computer automatic test system to test the pyroelectric coefficient of crystals with different thickness and surface roughness. The pyroelectric coefficient of crystal achieved 203 μC·m^-2k^-1 proves the favorable pyroelectric properties.

Abstract: X-ray emission using pyroelectric crystals is intermittent, and has low intensity and stability. One of the factors for low stability is related to creeping discharge, due to the accumulation of surface electric charges that change in response to the temperature. The time dependence of the net amount of electric charge was investigated by changing the cycle period of the crystal temperature. The stability of the X-ray emission is demonstrated to be strongly dependent on the temperature cycle period.

Abstract: The mechanism of pryoelectric-induced X-ray emission in LaTiO₃ crystals is discussed. It is suggested that electrons which contribute to the X-ray emission were generated around and close to the crystal and were emitted from the z surface. The poor reproducibility was found to be due to a creeping electrostatic discharge. It is speculated that one of the factors of the discharge is the accumulation of positive charges on the z surface.

Abstract: A ceramics sample of LiTaO3 was prepared using a sol-gel method. The sample is annealed at 750 °C for 48 hours. X-ray diffraction analysis indicate the formation of single phase, rhombohedral structure. An ac impedance study was used to analyse the conductivity of LiTaO3 at room temperature and at various temperatures.

Abstract: Preparation of LiTaO3 was done using the sol-gel method which is also known as the wet chemical technique. Thermal analysis (TG-DSC) of LiTaO3 precursor was studied to determine an optimized heating temperature. LiTaO3 was heated at 550 °C with different sintering time of 12, 24, 48 and 72 h. The formation of pure LiTaO3 occurred during sintering time of 72 h which was confirmed using X-ray diffraction (XRD). The morphology of pure LiTaO3 was recorded using a Scanning Electron Microscope (SEM). Pure LiTaO3 can only be formed at a longer heating time in order to complete the oxidation process.

Abstract: Three and six LiTaO₃ single crystals are used to achieve continuous emission of high-intensity X-rays. Furthermore, the interaction between X-rays and the case of the X-ray source is used to generate electrons. X-rays were emitted continuously and fluctuations in the count rate were reduced when three or six crystals were used. Moreover, the X-ray intensity increased and the number of electrons generated by the above-mentioned interaction increased with increasing number of crystals.

Abstract: Materials with an average particle size of less than about 50 nm often show new or at least enhanced physical properties. In many cases nanocrystalline ionic conductors exhibit a high increase of cation, e. g. Li+, or anion, e. g. F−, diffusivity. In the present contribution we review recent studies on ion dynamics in nanocrystalline ion conductors, both single-phase systems and composites, being prepared by high-energy ball milling. These include, e.g., LiTaO3, Li2O:Al2O3, LiF:Al2O3, BaF2, CaF2, BaF2:CaF2 and (BaF2:CaF2):Al2O3. Dynamic properties were probed by 7Li and/or 19F NMR line shape and relaxation as well as ion conductivity measurements.

Abstract: The Al2O3/LiTaO3 (ALT) composite ceramics were fabricated by hot pressing method and polarization treated at different temperatures along height and width directions. Effects of polarization treatment on mechanical properties of the ALT composite ceramic were investigated. Flexural strength decreased with the increase of polarization temperature. Meanwhile, the flexural strength of samples polarized in height direction is higher than that polarized in width direction. The composite ceramic fractures intragranularly, and many rupture steps in polarization direction were observed on fractographs of the composite ceramics. Domain switching in LiTaO3 particles increased the resistance of crack propagation and improved the mechanical properties of the polarized ALT composite ceramics.

Abstract: Effects of different sintering methods such as pressureless sintering and hot press sintering on relative density and microstructure of the Al2O3p/LiTaO3 (ALT) composite ceramics were investigated to obtain a preferable sintering process. Relative densities of all ALT composites are below 90% when sintered with the cold isostatical pressing followed by pressureless sintering at temperatures of 1250 to 1350°C. The relative densities and microstructure of ALT composite ceramics with the hot press sintering process in a N2 atmosphere at 1150 and 1300°C were investigated. The relative density of ALT composite hot pressed at 1150°C is only 77%, and almost theoretical density at 1300°C. This indicates that sintering pressure plays an important role in the densification of ALT composite ceramics in temperature range of 1150 to 1350°C. Investigation on morphologies of the composites shows that the Al2O3 particles distributed along grain boundaries of LiTaO3, which leads to a fine-grained microstructure in the ALT composite ceramics