Sol-gel synthesis, structure, and dielectric properties of La0.67LixTi1-xAlxO3 solid solutions

La0.67LixTi1-xAlxO3 were synthesized using the sol-gel Pechini route. Ceramic samples were sintered in the temperature range of 1240–1300 °C in the air atmosphere. It was found that in the concentration range of 0.05 ≤ x < 0.15 there is a morphotropic phase boundary region with rhombohedral and tetragonal syngonies. In the concentration range of 0.15 ≤ x ≤ 0.3, a single-phase solid solution with rhombohedral R 3‾ c syngony is formed. As the value of x increases, the average grain size of La0.67LixTi1-xAlxO3 ceramics increases from 5.23 μm (x = 0.05) to 8.76 μm (x = 0.3). All materials of the La0.67LixTi1-xAlxO3 system at 0.05 ≤ x ≤ 0.3 have colossal values of dielectric constant ε′ > 104 at frequencies up to 1 kHz. La0.67LixTi1-xAlxO3 (x = 0.2) solid solution with rhombohedral syngony has the highest value of dielectric constant and the lowest value of the dielectric losses.