The Ginzburg-Landau theory on ferroelectrics with random field induced by dipole defects is studied by using Monte Carlo simulation, in order to investigate the dipole configuration and the dielectric relaxation of re...The Ginzburg-Landau theory on ferroelectrics with random field induced by dipole defects is studied by using Monte Carlo simulation, in order to investigate the dipole configuration and the dielectric relaxation of relaxor ferro-electrics. With the increase of random field, the dipole configuration evolves from the long-range ferroelectric order into the coexistence of short-range dipole-clusters and less polarized matrix. The dipole-cluster phase above the transition temperature and superparaelectric fluctuations far below this temperature are identified for the relaxor ferroelectrics. We investigate the frequency dispersion and the time-domain spectrum of the dielectric relaxation, demonstrating the Vogel-Fulcher relationship and the multi-peaked time-domain distribution of the dielectric relaxation.展开更多
High-performance relaxor ferroelectric single crystals Pb(Mg1/3Nb2/3)O3-PbTiO3 have been grown successfully by a modified Bridgman method. They have the size of 25×25×50 mm3 and are of pure perovskite phases...High-performance relaxor ferroelectric single crystals Pb(Mg1/3Nb2/3)O3-PbTiO3 have been grown successfully by a modified Bridgman method. They have the size of 25×25×50 mm3 and are of pure perovskite phases with tetragonal or rhombohedral structures. Their {001} faces appear dominantly, which can be interpreted by the model of an-ionic coordination polyhedral growth units. Main macro defects observed under optical microscopes and SEM can be reduced or removed by improving growth parameters after understanding their formation mechanism. 71°or 109°macrodomains in rhombohedral PMNT 76/24 crystals and 90°macrodomains in tetragonal PMNT 65/35 crystals have been observed by optical microscopes. It has been found that the transition from microdomains to macrodomains can be induced by compositions. Both the imaging mechanism of non-180° domains and the relation between domain configurations and ferroelectric phase transition have been analyzed.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos.50832002 and 10874035)the National Basic Research Program of China (Grant No.2009CB623303)
文摘The Ginzburg-Landau theory on ferroelectrics with random field induced by dipole defects is studied by using Monte Carlo simulation, in order to investigate the dipole configuration and the dielectric relaxation of relaxor ferro-electrics. With the increase of random field, the dipole configuration evolves from the long-range ferroelectric order into the coexistence of short-range dipole-clusters and less polarized matrix. The dipole-cluster phase above the transition temperature and superparaelectric fluctuations far below this temperature are identified for the relaxor ferroelectrics. We investigate the frequency dispersion and the time-domain spectrum of the dielectric relaxation, demonstrating the Vogel-Fulcher relationship and the multi-peaked time-domain distribution of the dielectric relaxation.
基金Project supported by the National Natural Science Foundation of China (No. 59995520), the Chinese Academy of Sciences and Shanghai Municipal Government.
文摘High-performance relaxor ferroelectric single crystals Pb(Mg1/3Nb2/3)O3-PbTiO3 have been grown successfully by a modified Bridgman method. They have the size of 25×25×50 mm3 and are of pure perovskite phases with tetragonal or rhombohedral structures. Their {001} faces appear dominantly, which can be interpreted by the model of an-ionic coordination polyhedral growth units. Main macro defects observed under optical microscopes and SEM can be reduced or removed by improving growth parameters after understanding their formation mechanism. 71°or 109°macrodomains in rhombohedral PMNT 76/24 crystals and 90°macrodomains in tetragonal PMNT 65/35 crystals have been observed by optical microscopes. It has been found that the transition from microdomains to macrodomains can be induced by compositions. Both the imaging mechanism of non-180° domains and the relation between domain configurations and ferroelectric phase transition have been analyzed.
