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Information × Registration Number 0205U007031, 0101U007171 , R & D reports Title Effects of external fields and disorder in ferroelectric order-disorder type ferroelectrics popup.stage_title Head Levyts'kyj Roman Romanovych, Registration Date 08-12-2005 Organization Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine popup.description2 Within the project we have developed a microscopic approach to description of phase transitions in ferroelectric order-disorder type crystals, including those with hydrogen bonds, have calculated their physical characteristics with taking into account tunneling and piezoelectric effects. We have developed a modificaton of a four-state model suitable for description of a sequence of phase transitions, thermodynamics and dielectric properties of DMAGaS and DMAAlS ferroelectrics, as well as their dependences on hydrostatic pressure. We have taken into account the influence of Gaussian fluctuations. We have explored the nature and role of short-range and long-range interactions, deformational (piezoelectric) effects in the phase transitions in ferroelectric crystals of the KH2PO4 familty and Rochelle salt. Mechanisms of formation of short-range configurational interactions in model hydrogen bonded systems have been studied ab initio. We have performed theoretical and experimental studies of influence of deuteration, humidity, thermal annealing, hydrostatic pressure, shear stresses and electric fields on phase transitions, dielectric, piezoelectric, and elastic characteristics of the KH2PO4 family and Rochelle salt crystals. Product Description popup.authors popup.nrat_date 2020-04-02 Close