  X-ray diffraction with synchrotron radiation has been used for the first time
to study chemical interaction in the MnO-ZnO system at 4.8 GPa and temperatures
up to 1600 K. Above 750 K, the chemical reaction between MnO and ZnO has been
observed that resulted in the formation of rock salt (rs) Mn1-xZnxO solid
solutions (0.3 \leq x \leq 0.7). The lattice parameters of these solid
solutions have been in situ measured at high pressure as a function of
temperature, and corresponding thermal expansion coefficients have been
calculated.
