Papers by Keyword: Lithium Tantalate

Abstract: A method was developed for synthesis of a single phase lithium tantalate charge doped by rare earth elements (TR) from highly pure solutions containing tantalum. The method is based on obtaining and thermal treatment of citrate precursor containing Li, Ta and TR. Charge samples were obtained due to suggested technological scheme; the dopant had given concentration and was chemically uniformly distributed. The charge can be applied both in single crystal growing technology and at obtaining of functional ceramics based on LiTaO₃:TR.

Abstract: This paper reports our recent results on the nanoindentation and nanoscratch of LiTaO3 single crystals. The elastic modulus and hardness of LiTaO3 obtained from nanoindentation were 251±3 GPa and 12.6±0.6 GPa, respectively. During indenting, pop-in events occurred when indentation load was in the range from 305 to 640 μN. Incipient kink bands (IKBs) were believed to be responsible for the pop-ins. Nanoscratching showed that there existed a threshold normal load of 2.5 mN, above which cracks were generated and the material removal was in the brittle regime. The knowledge gained is valuable to the design of an effective machining process for LiTaO3 crystals.

Abstract: The novel lithium enriched lithium tantalate (LiTaO₃) targets were papered by employing the sol-gel process and the high temperature sintered process. The sol of LiTaO₃ was firstly prepared through reacting lithium ethoxide with tantalum ethoxide. The LiTaO₃ powder was fabricated by presintered LiTaO₃ dry gel 4 hour, at 800°C. The 11cm13cm1cm lithium enriched LiTaO₃ target samples were prepared by sintered the pressed LiTaO₃ powder billet 4 hour in the 850°C muffle furnace. The density of the 5% overdose lithium enriched LiTaO₃ target is measured 5.96g/cm³. The XRD measured results show that the ion beam enhanced deposited (IBED) thin film samples using the prepared 5% overdose lithium enriched LiTaO₃ target have the polycrystal structure of LiTaO₃, but there has remanent Ta₂O₅ existed in the IBED thin film samples. The main reason for the remanent Ta₂O₅ growth was due to the stoichiometric proportion mismatch between Li and Ta in the IBED thin film samples during the high temperature annealed process, which caused the lithium oxide evaporation loss from the IBED thin film samples and made the proportion of Ta₂O₅ increase. After multipule repeated target prepared experiments, the 8.76% overdose lithium enriched LiTaO₃ target is suitable for fabricating the 550°C annealed IBED LiTaO₃ thin film. After the repeated process experiments, the suitable deposited process parameters of the IBED-C600M instrument for the 8.76% overdose lithium enriched LiTaO₃ target were obtained. The SEM micrographs of the 550°C annealed IBED LiTaO₃ thin films prepared by the 8.76% overdose lithium enriched LiTaO₃ target reveal the prepared thin films are uniform, smooth and crack-free on the surface, and the perfect adhesion between the thin film and the substrate. The successfully fabricated LiTaO₃ thin film samples verify the prepared processes of novel LiTaO₃ sputtering target are effective.

Abstract: The Ion Beam Enhanced Deposited (IBED) lithium tantalate (LiTaO₃) thin film samples with Al/LiTaO₃/Pt electrode structure were prepared on the Pt/Ti/SiO₂/Si(100) and SiO₂/Si(100) substrate respectively. The crystallization, surface morphology, ferroelectric property, and fatigue property of the prepared samples with the different annealed processes were investigated. The XRD measured results show that the prepared samples have the polycrystal structure of LiTaO₃ with the preferred orientation of <012> and <104> located at the 2θ of 23.6⁰ and 32.7⁰ respectively. The SEM morphology analysis reveals the prepared film annealed at 550°C is uniform, smooth and crack-free on the surface and cross section. The ferroelectric property measured results show that the remanent polarization Pr of the samples annealed at different temperature almost increase with the electric field intensity stronger. The leakage current makes the hysteresis loop of the samples subjected to a strong measured electric filed difficult to appear the same saturation hysteresis loop as the single-crystal LiTaO₃. The prepared samples annealed at 550°C have a Pr value of 11.5μC/cm² when subjected to the electrical field of 400kV/cm. The breakdown voltage of the 587nm thick thin film sample is high as to 680 kV/cm. The fatigue property measured results show only 15.17% Pr drop of the prepared films annealed at 550°C appear after 5×1010 cycles polarized by the 10MHz sinusoidal signal with the peak-to-peak amplitude of 10 Volt. The ferroelectric properties of the prepared films meet the practical application requirements of charge response measurement of the LiTaO₃ infrared detector owe to the Pr of the prepared films annealed at different temperature large beyond 10μC/cm² when the prepared films subjected to a strong electric filed larger than 400 kV/cm. The experimental results also show that the surface morphology, the ferroelectric and fatigue properties of the IBED LiTaO₃ thin films are significant better than those of the Sol-Gel derived LiTaO₃ thin films.

Abstract: LiTaO3 is an important optical material. It may also be possible to use this material as a solid electrolyte for lithium-ion batteries which may be applicable in thin film solid-state batteries. Generally, ceramics have a wide range of impedances. Many ceramics have mixed charged species consisting of electronic as well as ionic charge carriers. This work investigates the conductivity of LiTaO3 materials using ac impedance spectroscopy technique measured as a function of temperature.

Abstract: Na2O excess 95(Na0.5K0.5)NbO3-5LiTaO3 (NKN-5LT) ceramics were developed by conventional sintering process. Sintering temperature was lowered by adding Na2O as a sintering aid. Grain growth behaviors with Na2O addition were explained in terms of the effect of Na2O on interface reaction - controlled grain growth and the critical driving force. The electrical properties of NKN-5LT ceramics were investigated as a function of Na2O concentration. In the 1 mol% Na2O excess NKN-5LT samples sintered at 1000oC for 4h in air, electromechanical coupling factor (kP) and piezoelectric coefficient (d33) of NKN-5LT ceramics were found to reach the highest values of 0.43 and 190 pC/N, respectively.