Annealing Effect on the Ionic Conductivity of La0.67-xLi3xTiO3 Made by Double Mechanical Alloying Method

Abstract

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.

Characterization of structure and Li-ionic conductivity of La\(_{(2/3−x)}\)Li\(_{3x}\)TiO\(_{3}\) ceramics prepared by spark plasma sintering

“…La 2/3−x Li 3x TiO 3 nanopowder with x = 0.09 (LLTO) was prepared by mechanical alloying method using La 2 O 3 (Aldrich -99.9%), Li 2 CO 3 (Aldrich -99%) and TiO 2 (Aldrich -99%) as source materials. The LLTO nanopowder preparation process using Fritsch model Pulverisette 6 high kinetic energy planetary mill has been reported in our previous work [15]. To obtain coinshaped LLTO ceramic samples, the SPS system (LABOX-210, Sinter Land Corporation, Japan) was used.…”

“…The research results also show that the lithium-ion conductivity of LLTO ceramics depends on the crystal structure and microstructure [6][7][8], the concentration of lithium-ion and the A-site vacancies [6,7,9,10], the chemical homogeneity [5,11], the sizes of grain and grain boundaries [12,13] and material density [3]. The influence of these factors on the electrical conductivity of LLTO can be adjusted through the methods of initial LLTO powder preparation, temperature, time and sintering procedure [3,5,7,[14][15][16][17][18]. Therefore, preparation technology has always played an important role to obtain LLTO ceramics with desired properties.…”

“…In recent years, a high-energy ball mill method has been applied that allows LLTO powder to be obtained even at low temperature, with fairly uniform particle size, and to avoid loss of lithium when calcined at high temperature in a long time [15]. Furthermore, spark plasma sintering (SPS) is also used to prepare highly dense LLTO ceramics even at low temperature, in a short time [13,[23][24][25].…”