Ag. Belous et al., Solid-state reaction mechanism for the formation of Ba(6-x)Ln(8+2) x/3Ti18O54 (Ln = Nd, Sm) solid solutions, J MATER RES, 16(8), 2001, pp. 2350-2356
A solid-state reaction mechanism for the formation of Ba(6-x)Ln(8+2x/3)Ti(1
8)O(54) (Ln = Nd, Sm) solid solutions has been studied using x-ray powder d
iffraction, thermal analyses, and transmission electron microscopy (TEM). D
uring the interaction of the starting reagents, Ln(2)Ti(2)O(7), BaTi4O9, an
d BaTiO3 are formed. In the next sequence, these three phases react togethe
r to form a high-x end member of the Ba(6-x)Ln(8+2x/3)Ti(18)O(54) homogenei
ty region (Ba3.9Nd9.4Ti18O54 and Ba3.9Sm9.4Ti18O54). Subsequently, the reac
tion of Ba3.9Nd9.4Ti18O54 and Ba3.9SM9.33Ti18O54 with the residual BaTiO3 t
akes place. TEM investigations revealed that compositional inhomogeneities
and structural defects existed in the Ba4SM9.33Ti18O54 sample heated at 137
0 degreesC for 1 h. Sintering times, prolonged to greater than or equal to3
h, eliminated the structural defects and increased the homogeneity of them
sample.