Electric field-induced phase transitions in (111)-, (110)-, and (100)-oriented Pb(Mg1â‹Ł3Nb2â‹Ł3)O3 single crystals

Electric field-induced phase transitions were investigated in (111), (110), and (100) thin platelets of relaxor ferroelectric Pb(Mg1∕3Nb2∕3)O3 single crystals with electric fields applied along the ⟨111⟩, ⟨110⟩, and ⟨100⟩ directions, respectively. Temperature dependences of complex dielectric permittivity, pyroelectric current and dielectric hysteresis loops were investigated. Electric field-temperature (E-T) phase diagrams were proposed for the different directions of the field. Alongside with the high-temperature ergodic relaxor phase and the low-temperature glassy nonergodic relaxor phase existing at E=0, the ferroelectric phase may appear in the diagram at the fields higher than the threshold field (Eth). The temperature of the first-order transition between ergodic relaxor and ferroelectric phases (TC) was located in field cooling and field heating after fieldcooling regimes. For the ⟨111⟩ field direction, TC is higher and Eth is lower than for the other directions. For the ⟨100⟩ direction, TC is the lowest and Eth is the highest. The critical point bounding the TC(E) line when the field is applied in ⟨111⟩ direction [ Z. Kutnjak, J. Petzelt and R. Blinc Nature 441 956 (2006)] is not observed in the ⟨110⟩ and ⟨100⟩ directions up to the highest applied field of 7.5 kV∕cm. Extrapolation of experimental data suggests that the critical point for the ⟨110⟩ and ⟨100⟩ directions (if any) can be expected only at much higher fields. In the hysteresis loops experiments performed after zero-field cooling, the lower temperature limit is determined above which a ferroelectric phase can be induced from the frozen glassy state at a given field strength or the polarization of the induced ferroelectric phase can be reversed. This limit is located at much lower temperatures in the (100) platelet than in the (110) or (111) platelets. An additional ferroelectric rhombohedral to ferroelectric orthorhombic phase transition occurs in the (110) platelet at high electric fields (∼20 kV∕cm). The mechanisms of the field-induced transformation from the glassy nonergodic relaxor phase or the ergodic relaxor phase to the ferroelectric phase are discussed. Disciplines Ceramic Materials | Materials Science and Engineering | Physical Chemistry Comments This article is from Physical Review B 75 (2007): 104106, doi:10.1103/PhysRevB.75.104106. This article is available at Iowa State University Digital Repository: http://lib.dr.iastate.edu/mse_pubs/22 Electric field-induced phase transitions in (111)-, (110)-, and (100)-oriented Pb„Mg1/3Nb2/3...O3 single crystals X. Zhao, W. Qu, and X. Tan* Department of Materials Science and Engineering, Iowa State University, Ames, Iowa 50011, USA A. A. Bokov and Z.-G. Ye Department of Chemistry, Simon Fraser University, Burnaby, B.C. Canada V5A 1S6 Received 22 June 2006; revised manuscript received 15 January 2007; published 13 March 2007 Electric field-induced phase transitions were investigated in 111 , 110 , and 100 thin platelets of relaxor ferroelectric Pb Mg1/3Nb2/3 O3 single crystals with electric fields applied along the 111 , 110 , and 100 directions, respectively. Temperature dependences of complex dielectric permittivity, pyroelectric current and dielectric hysteresis loops were investigated. Electric field-temperature E-T phase diagrams were proposed for the different directions of the field. Alongside with the high-temperature ergodic relaxor phase and the low-temperature glassy nonergodic relaxor phase existing at E=0, the ferroelectric phase may appear in the diagram at the fields higher than the threshold field Eth . The temperature of the first-order transition between ergodic relaxor and ferroelectric phases TC was located in field cooling and field heating after field-cooling regimes. For the 111 field direction, TC is higher and Eth is lower than for the other directions. For the 100 direction, TC is the lowest and Eth is the highest. The critical point bounding the TC E line when the field is applied in 111 direction Z. Kutnjak, J. Petzelt, and R. Blinc, Nature 441, 956 2006 is not observed in the 110 and 100 directions up to the highest applied field of 7.5 kV/cm. Extrapolation of experimental data suggests that the critical point for the 110 and 100 directions if any can be expected only at much higher fields. In the hysteresis loops experiments performed after zero-field cooling, the lower temperature limit is determined above which a ferroelectric phase can be induced from the frozen glassy state at a given field strength or the polarization of the induced ferroelectric phase can be reversed. This limit is located at much lower temperatures in the 100 platelet than in the 110 or 111 platelets. An additional ferroelectric rhombohedral to ferroelectric orthorhombic phase transition occurs in the 110 platelet at high electric fields 20 kV/cm . The mechanisms of the field-induced transformation from the glassy nonergodic relaxor phase or the ergodic relaxor phase to the ferroelectric phase are discussed. DOI: 10.1103/PhysRevB.75.104106 PACS number s : 77.80.Bh, 77.22.Ch, 77.84.Dy