Mechanochemical Synthesis of LaOX (X=Cl, Br) and Their Solid State Solutions

A mixture of lanthanum oxide (La₂O₃), chloride (LaCl₃), and bromide (LaBr₃) was ground in air by a planetary ball mill to investigate synthesis of lanthanum oxychloride (LaOCl), oxybromide (LaOBr), and their solid solutions, LaOCl_1−xBr_x (0≤x≤1, Δx=0.25). The synthesizing reactions proceed with an increase in grinding time. Unit cell dimensions, a, c, and lattice volume of the solutions evolve linearly with an increase in x in the LaOCl_1−xBr_x series. Comparing unit cell dimensions of LaOX synthesized by mechanochemical reaction to those of LaOX synthesized by solid-state reaction at high temperature, there is no difference in the length of c, while a is shortened slightly. This may be attributed to the complex cation layer of (LaO)ⁿ⁺_n, with a close relationship to a of the cell dimensions, being affected by the intensive grinding.