Effect of the Hydrostatic Pressure on the Ferroelastic NdP₅O₁₄

Abstract

The effects of the hydrostatic pressure on the ferroelastic NdP₅O₁₄ were investigated both by crystal-optic methods and the single crystal X-ray diffraction technique, using three types of diamond anvil cells. The monoclinic to orthorhombic phase transition temperature T_c was found to increase with increasing pressure with the initial slope of dT_c⁄dP∼38 K/kb. A marked increase of monoclinic distortion angle δ and the associated increase of the half angle of the extinction positions between the two neighboring ferroelastic domains θ were observed with the increase of applied hydrostatic pressure. Pressure effects on the above measured quantities are discussed.