Raman study of the ferroelectric phase transition in PbHPO4and PbHAsO4

摘要

The Raman spectra of PbHPO4and PbHAsO in theparahyphen; and ferroelectric phases and also PbDAsO4(room temperature only) have been measured. Mode assignment of most predicted modes has been made. Weak underdamped soft modes have been observed below 100 cmminus;1in the ferroelectric phase of both hydrogen compounds which confirms the role of the proton tunnelling in the double minimum potential. PbDAsO4seems not to be isomorphous to PbHAsO4at room temperature.