Pressure-induced Phase Transitions of LnX (Ln=lanthanide, X=P, As and Sb) with a NaCl-type Structure

By use of synchrotron radiation, the powder x-ray diffraction of LnX (Ln=lanthanide, X=P, As and Sb) with a NaCl-type structure has systematically been studied at high pressures. Pressure-induced phase transitions of LnX were found at room temperature. The transition pressure is highest for LnP and lowest for LnSb. In this report the phase transitions of LnSb at high pressure are mainly described. The high-pressure form of LnSb is classified into three groups. The lighter LnSb (Ln=La, Ce Pr and Nd) have a tetragonal structure (distorted CsCl-type) at high pressures. The structure of the high-pressure phase of the middle LnSb (Ln=Sm, Gd and Tb) is unknown. The heavier LnSb (Ln=Dy, Ho, Er, Tm and Lu) shows the typical NaCl-CsCl transition at high pressures. The high-pressure structural behavior of LnX is discussed.