Anomalous phase transition in shock-compressed PbO

Transformation of the rhombic modification of lead monoxide into a tetragonal form with a lower density under shock compression in the range of pressures of 9.5 – 35 GPa has been observed. It is shown that the anomalous phase transition occurs only in the porous material, and the yield of the new phase increases with decreasing temperature, i.e., results from the mechanical action of the shock wave. Specific features of the shock-wave transformation of lead monoxide compared to an analogous effect caused by grinding and static compression with shear are discussed.