Bulk nanostructured perovskites of La 0.67-x Li 3x TiO 3 (LLTO) were prepared by using thermally ball-grinding from compounds of La 2 O 3 , Li 2 CO 3 and TiO 2 . From XRD analysis, it was found that LTTO materials were crystallized with nano-size grains of an average size of 30 nm. The bulk ionic conductivity was found strongly dependent on the Li + composition, the samples with x = 0.11 (corresponding to a La 0.56 Li 0.33 TiO 3 compound) have the best ionic conductivity, which is ca. 3.2 x 10 -3 S/cm at room temperature. The LLTO amorphous films were made by electron beam deposition. At room temperature the smooth films have ionic conductivity of 3.5 x 10 -5 S/cm and transmittance of 80%. The optical bandgap of the films was found to be of 2.3 eV. The results have shown that the perovskite La 0.56 Li 0.33 TiO 3 thin films can be used for a transparent solid electrolyte in ionic battery and in all-solid-state electrochromic devices, in particular.
Crystalline perovskite La0.67-xLi 3x TiO 3 with x = 0.06, 0.11 and 0.15 were prepared by solid-state-solution reactions at 1350 0 C from TiO 2 , La 2 O 3 and Li 2 CO 3 Crystalline structure of these compounds was analyzed by XRD method. The ionic conducting property of La 0.67-x Li 3xTiO 3 was characterized on AutoLab. Potentiostat-PGS30 system with impedance technique using fitting software program available in the equipment. The highest ion conductivity at room temperature was found for the compound with x =0.11, namely $\sigma$ = 3.1 x 10 -5Scm -1. With increase of temperature the ionic conductivity increased and at 2000C it reached a value in two orders in magnitude higher (6 x 10 -3Scm -1). The activation energy of the compounds was determined on Ln($\sigma$) vs. 1/T plots and found to be as low as 0.36 eV.
With the aim of producing all-solid-state electrochromic mirrors, La 0.67−x Li 3x TiO 3 (LLTO) and the WO 3 were prepared by electron beam deposition. The LLTO (with x = 0.11) powder was synthesized by thermally ball-grinding method and the Li + ionic conductivity of the LLTO ceramic targets was found to be of ca. 3.25 × 10 −3 S/cm. Using LLTO targets for e-beam evaporation, 300 nm-thick films with the Li + ionic conductivity of 5.50 × 10 −5 S/cm were deposited. Combining LLTO films with WO 3 /ITO and LiMn 2 O 4 layers, all-solid-state electrochromic mirrors with a laminar structure of Al/LiMn 2 O 4 /LLTO/WO 3 /ITO were prepared. The reversible reflectance of the mirrors was well controlled by applying polarized potentials onto the ITO electrode. The obtained results suggest useful applications for electrochromic windows working as a smart reflectance mirror that can be used for auto rear-view mirrors.
Perovskite La\(_{(2/3) - x}\)Li\(_{3x}\)TiO\(_{3}\) samples with 0.06 \( \leq x \leq 0.15\) were prepared by a double mechanical alloying method. Structure and Li$^{ + }$-ion conductive properties of the La\(_{(2 / 3) - x}\)Li\(_{3x}\)TiO\(_{3}\) samples were investigated. Most of the analyzed perovskite samples exhibit a double unit cell. In these samples, a change of symmetry from tetragonal to orthorhombic is observed for sample with lithium content x = 0.06. Structural modifications were obtained mainly due to the cation vacancies ordering along the c-axis, which disappeared gradually when the lithium content increased. At room temperature, the maximum values of grains and grain boundaries conductivities of the La\(_{(2 / 3) - x}\)Li\(_{3x}\)TiO\(_{3}\) samples were found to be of \(1.5\times 10$^{ - 3}\) S/cm and \(5.8 \times 10^{ - 5}\) S/cm, respectively. The temperature dependence of ionic conductivity obeyed a non-Arrhenius behaviour. At temperature from 30 to 125\(^{\circ}\)C, the activation energy for grain and grain-boundary conductivity was found to be of $\sim $ 0.23 eV and $\sim $ 0.32 eV, respectively.
Abstract. Perovskite La0.67−xLi3xTiO3 with x = 0.10, 0.11, 0.12 and 0.13 were firstly annealed at 800 o C then treated by reactive milling, followed by post-annealing at temperatures from 1100 to 1200 o C. The crystalline structure of grain and grain-boundary were characterized by XRD and SEM. The impedance measurements showed that nanocrystalline La0.67−xLi3xTiO3 after being annealed at 1150 o C possessed a grain conductivity as high as 1.3 × 10 −3 S.cm −1 . The grainboundary conductivity was enhanced one order in magnitude after annealing at temperature higher 1100˚C and consists of 5.8 × 10 −5 S.cm −1 . The results have also showed the limitation of the adiabatic thermal treatment for the improvement of the grain-boundary conductivity and suggested the way to overcome the limitation by rapidly cooling the samples from the high temperature to room temperature.
Perovskite La 2/3-x Li 3x TiO 3 with x = 0.11 (called LLTO11) powders were prepared by double mechanical alloying method from TiO 2 (99.99%), Li 2 CO 3 , (99.99%) and La 2 O 3 (99.9%) powders, in ideal cation stoichiometry for La 2/3-x Li 3x TiO 3 . The obtained single phase of LLTO11 powder was isostatically pressed under a pressure of 450 MPa and annealed at a temperature ranging from 1,100 °C to 1,250 °C. Optimal morphology and grain structure for the ionic conductivity of the samples were achieved at annealing temperature of 1,200 °C. For this ceramic, the lithium ionic grains and grain-boundaries conductivities at room temperature possess a value of 1.5 × 10 -3 S/cm and 4.8 × 10 -5 S/cm, respectively. The improvement in the grain-boundaries conductivity was explained due to the decrease of the number of grains, included grain boundaries and the diminution of the pores in LLTO samples annealed at 1,200 °C. The obtained results suggest useful applications of La (2/3)-x Li 3x TiO 3 (x = 0.11) ceramics for the production of the solid state electrolytes, for high-temperature Li-ionic batteries, in particular.
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