Pressure effects on the lattice parameters and structure of Kh2Po4-type crystals

Abstract

The effects of hydrostatic pressure (≤3 kbar) on the lattice parameters of KH2PO4-type crystals have been determined at 295°K from single crystal x-ray diffraction measurements. The axial compressibilities were calculated and compared with values obtained from elastic constant measurements. We have also measured the volume compression of KH2PO4 to 22 kbar using a piston displacement technique. The atomic positional parameters of KH2PO4 were examined at 1 bar and at 3 kbar from single crystal x-ray intensity measurements. Within experimental error, the atomic positions of the oxygen atoms, determined at 3 kbar, show no resultant pressure-induced rotation of the PO-34 groups. The implications of the results on the pressure dependence of the ferroelectric and antiferroelectric transitions in these crystals are discussed.