Origin of Ferroelectric Phase Transitions of BixSb1-xSI Mixed Crystals

• Published in: Ferroelectrics 2009-11, Vol.392 (1), p.45-54
• Main Authors: Audzijonis, A., Žigas, L., Kvedaravičius, A., Žaltauskas, R.
• Format: Article
• Language: English
• Subjects: 21.60.Gx; 36.40.-c; 61.50. Ah; 71.20.-b; 73.22.-f; BiSI; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Dielectrics, piezoelectrics, and ferroelectrics and their properties; electronic band structure; Exact sciences and technology; Ferroelectricity and antiferroelectricity; molecular cluster; Phase transitions and curie point; Physics; total density
• ISSN: 0015-0193; 1563-5112
• DOI: 10.1080/00150190903412481

The nature of normal modes' anharmonism of SbSI-type crystals is investigated in this work. In order to explain the nature of anharmonism we apply the normal vibration mode's average potential energy's dependence on amplitudes of normal coordinates along c (z)-axis. It is proved that the variation of potential barrier between two wells of double-well potential energy V p (z) is caused by temperature T, quasihidrostatic pressure p, and mixture x. The temperature dependence of ferroelectric phase transition on quasihidrostatic pressure p and mixture x is determined for SbSI and Bi x Sb 1-x SI crystals. Applying the equality is theoretically proved that there is no ferroelectric phase transition in Bi x Sb 1-x SI crystals where x > 0.7. The ferroelectric phase transition in SbSI-type crystals and Bi x Sb 1-x SI crystals is caused by the phonon interaction's dependence on temperature, pressure and mixture.