Ferroelectric Phase Transition and New Intermediate Phase in Bi-Layered Perovskite SrBi 2 Ta 2 O 9

Calorimetric Determination of Heat Capacity, Entropy and Enthalpy of Mixed Oxides in the System CaO–SrO–Bi2O3–Nb2O5–Ta2O5

“…The heat capacities of polycrystalline and monocrystalline SrBi2Ta2O9 and Sr0,85Bi2,1Ta2O9 have been measured by Onodera at al. [3][4][5] at 80-800 K. Morimoto at al. [6] have reported the results of the heat capacity measurements of SrBi2(NbxTa1-x)2O9 ( x = 0, 1/3, 2/3 a 1).…”

Correlation between displacive‐type ferroelectricity and electronic density of states near the Fermi level in SrBi2Ta2O9

“…The ferroelectric phase is induced by the structural phase transition from the Amam to the orthogonal A2 1 am structure. The transition temperature reported so far now is slightly ambiguous varying from 300 °C to 340 °C [15,17,[22][23][24]. More recently, it was reported [17,24] that there are successive phase transitions at about 613 K (T C2 ) and 850 K (T C1 ), and that the intermediate phase between T C1 and T C2 has an orthogonal symmetry Amam, while the ideal phase above T C1 has the I4/mmm structure.…”

“…The transition temperature reported so far now is slightly ambiguous varying from 300 °C to 340 °C [15,17,[22][23][24]. More recently, it was reported [17,24] that there are successive phase transitions at about 613 K (T C2 ) and 850 K (T C1 ), and that the intermediate phase between T C1 and T C2 has an orthogonal symmetry Amam, while the ideal phase above T C1 has the I4/mmm structure. It is well known that the ferroelectric polarization in SBT results from the tilts along the a-and b-axes, and a rotation around the c-axis of slightly distorted TaO 6 octahedra, in addition to relatively planar displacements between the (Bi 2 O 2 ) 2+ sheets and the (SrTa 2 O 7 ) 2-blocks along the a-axis [15,16,23,24].…”

“…More recently, it was reported [17,24] that there are successive phase transitions at about 613 K (T C2 ) and 850 K (T C1 ), and that the intermediate phase between T C1 and T C2 has an orthogonal symmetry Amam, while the ideal phase above T C1 has the I4/mmm structure. It is well known that the ferroelectric polarization in SBT results from the tilts along the a-and b-axes, and a rotation around the c-axis of slightly distorted TaO 6 octahedra, in addition to relatively planar displacements between the (Bi 2 O 2 ) 2+ sheets and the (SrTa 2 O 7 ) 2-blocks along the a-axis [15,16,23,24]. Recently, there are many investigations to find a correlation between the ferroelectricity and the A-site modulated ABi 2 Ta 2 O 9 (A = Ba, Ca, and Sr), substituted compounds Sr 1-x A x Bi 2 Ta 2 O 9 , or vacant compounds Sr 1-x-y Bi x □ y Bi 2 Ta 2 O 9 , as it is expected that the A-site ion plays a crucial role to characterize the ferroelectricity as a giant polarization [15,16,[23][24][25].…”

“…It is well known that the ferroelectric polarization in SBT results from the tilts along the a-and b-axes, and a rotation around the c-axis of slightly distorted TaO 6 octahedra, in addition to relatively planar displacements between the (Bi 2 O 2 ) 2+ sheets and the (SrTa 2 O 7 ) 2-blocks along the a-axis [15,16,23,24]. Recently, there are many investigations to find a correlation between the ferroelectricity and the A-site modulated ABi 2 Ta 2 O 9 (A = Ba, Ca, and Sr), substituted compounds Sr 1-x A x Bi 2 Ta 2 O 9 , or vacant compounds Sr 1-x-y Bi x □ y Bi 2 Ta 2 O 9 , as it is expected that the A-site ion plays a crucial role to characterize the ferroelectricity as a giant polarization [15,16,[23][24][25]. In order to theoretically study a correlation between the electronic structure and the ferroelectricphotoelectronic properties of SBT, the electronic band structure has been analyzed by tight-binding methods [26], discrete variational Xα method [27], first-principles method [28 -31], etc.…”