Features of the doping effect on YAlO$_3$ phase sequences during synthesis from an amorphous precursor state

Using X-ray diffraction methods, it has been shown that small lanthanum (La) dopants during solid-phase synthesis of YAlO$_3$ from an amorphous precursor state initiate the formation of the high-temperature hexagonal modification of yttrium aluminate in the first crystallization stages, whereas the equilibrium perovskite phase has an orthorhombic cell. At the same time, during YAlO$_3$ synthesis without dopants, yttrium-aluminum garnet Y$_3$Al$_5$O$_{12}$ is formed in the first crystallization stages, rather than the perovskite modification, as it follows from the precursor stoichiometry. The effect of lanthanum dopants on YAlO$_3$ phase sequences during synthesis from the amorphous precursor state is qualitatively explained.