Portal de Periódicos da CAPES

Structural parameters determining the transition temperature of tetragonal KH 2 PO 4 -type crystals

2001; American Physical Society; Volume: 64; Issue: 10 Linguagem: Inglês

10.1103/physrevb.64.100101

1095-3795

M. Ichikawa, Daisuke Amasaki, Torbjörn Gustafsson, I. Olovsson,

Crystal Structures and Properties

A systematic study of the structural parameters determining the ferroelectric phase transition temperature ${T}_{c}$ in tetragonal ${\mathrm{KH}}_{2}{\mathrm{PO}}_{4}$ (KDP)-type crystals ${\mathrm{MH}}_{2}{\mathrm{XO}}_{4}$ has been performed by searching the correlation between different structural parameters and ${T}_{c}.$ It has been revealed that the transition temperature is determined not only by the hydrogen-bond distance R, as reported earlier, but also by the distortion of ${\mathrm{XO}}_{4}$ (via O-X-O angle ${\ensuremath{\alpha}}_{1})$ and the packing of M and ${\mathrm{XO}}_{4}$ along the c axis (via the rotation angle $\ensuremath{\theta}$ around the c axis); ${\ensuremath{\alpha}}_{1}$ reflects the dipole moment of ${\mathrm{XO}}_{4}$ and $\ensuremath{\theta}$ may influence the amplitude of optical vibration of M and ${\mathrm{XO}}_{4}.$ The contribution of each structural part to the transition temperature ${T}_{c}$ in the tetragonal KDP family has been revealed in a comprehensive way for ferroelectrics.