Structural parameters determining the transition temperature of tetragonalKH2PO4-type crystals - art. no. 100101

A systematic study of the structural parameters determining the ferroelectr ic phase transition temperature T-c in tetragonal KH2PO4 (KDP)-type crystal s MH2XO4 has been performed by searching the correlation between different structural parameters and T-c. It has been revealed that the transition tem perature is determined not only by the hydrogen-bond distance R, as reporte d earlier, but also by the distortion Of XO4 (via O-X-O angle alpha (1)) an d the packing of M and XO4 along the c axis (via the rotation angle theta a round the c axis); alpha (1) reflects the dipole moment Of XO4 and theta ma y influence the amplitude of optical vibration of M and XO4. The contributi on of each structural part to the transition temperature T-c in the tetrago nal KDP family has been revealed in a comprehensive way for ferroelectrics.