Ferroelectric and Piezoelectric Properties of Single Crystals of Ba_<1-x>K_xTiO_<3-x>F_x with x=0.1(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

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Cubic and hexagonal BaTiO_3 single crystals doped with KF (Ba_<1-x>K_xTiO_<3-x>F_x with x=0.1) were grown from a solution with a molar ratio of BaO+2TiO_2+10KF. The cubic BaTiO_3 crystals with x=0.1 undergo a second order ferroelectric phase transition at the Curie temperature T_c of 35℃; the dielectric constant e′along the [100] direction shows a peak at T_c reaching 12000. Further, a spontaneous polarization appears below T_C; the remanent polarization P_r and the coercive field E_c are 7μCcm^<-2> and 1.3 kV/cm at 20℃, respectively. Furthermore, a large piezoelectric constant d_<33>=300pC/N was observed at 20℃. On the other hand, in hexagonal BaTiO_3 with x=0.1, e′along the hexagonal c-axis increases monotonously with decreasing temperature and saturates at low temperatures like quantum paraelectrics.
社団法人日本物理学会の論文
2006-07-15