Compact Li-doped Gd2Ti2O7 prepared with LiO0.5 self-flux

• A new series of compounds with a formula as (Gd2−xLix)Ti2O7−x was synthesized.
• Each GLT-2L sample contains (Gd2−xLix)Ti2O7−x and 2x moles of LiO0.5 self-flux.
• 1250 °C was used to prepare the GLT-2L samples; 300 °C lower than required.
• Electrical conductivity of the GLT-2L is not affected by the presence of the flux.
• Average valence of the Ti ions is slightly less than 4.

A series of (Gd2−xLix)Ti2O7−x with x = 0.040–0.110 was first reported. Parent compound with 2x moles of LiO0.5 self-flux was prepared at 1250 °C and abbreviated as GLT-2L. Relative density of all the samples is higher than 92%. By the addition of flux and Li ions substitution, preparation temperature is lowered for more than 300 °C. Comparing the unit cell a-axis, GLT with a formula as (Gd2−xLix)Ti2O7−x without flux addition has exactly the same as the GLT-2L with the same x. By the addition of flux, materials become more compact and grains grow bigger for the GLT-2L than the corresponding GLT samples. Electrical conductivity of a GLT-2L with x = 0.110 at 700 °C is 3 times larger than the measurements done by other research groups in the Gd2Ti2O7. In order to demonstrate the successful substitution of the Li ion into the Gd site, a series of GT samples was prepared with a formula of Gd2−xTi2O7−1.5x. With the same amount of x, every GLT samples have a longer unit cell a-axis than that of the GT. The difference is caused by the substitution of the Li ion into the Gd site. Valence of the Ti atoms of the GLT-2L samples is slightly less than 4 studied by the XANES spectroscopy.

Left figure is the unit cell a-axis of the GLT-2L (■), GLT (●) and GT (▴) as a function of x. Both of the GLT-2L and GLT have the same results so that they have the same chemical formula, (Gd2−xLix)Ti2O7−x, in which GT has a formula of Gd2−xTi2O7−x. Relative densities are shown in the right figure. GLT-2L (■) has higher values than GLT (●). 2x moles of LiO0.5 were added as a self-flux to prepare GLT-2L at 1250 °C, which was about 300 °C lowered than required without the co-existence of the flux and Li ion substitution.Figure optionsDownload as PowerPoint slide