  In solid-state electrochemical experiments, the boundary between the sample
and the electrolyte plays a crucial role, and the rest of the sample acting as
a buffer that maintains a fixed composition. Due to the presence of an
electrochemical circuit in the cell (ionic conductivity in the electrolyte and
electronic conductivity in the sample system), the chemical potential is
equalized at the electrolyte-sample boundary. This leads to an equilibrium
state and allows for the measurement of equilibrium values, regardless of the
assumptions made by the experimenters. This article demonstrates the principle
of equalizing the electrochemical potential at the electrolyte-sample
interface, which explains why achieving equilibrium in the presence of an
electrolyte can occur much faster compared to sample synthesis, which often
occurs at higher temperatures. This fact can be used to synthesize sample
systems or other substances at the required temperatures with a significant
reduction in synthesis time.
