Rösche Constanze, Boffa Ballaran Tiziana, Malcherek Thomas, Paulmann Carsten, Angel Ross John, Gorfman Semën, Mihailova Boriana
Department of Earth System Sciences, Universität Hamburg, Grindelallee 48, 20146, Hamburg, Germany.
Bayerisches Geoinstitut, Universität Bayreuth, Universitätsstraße 30, 95447, Bayreuth, Germany.
Sci Rep. 2024 Aug 13;14(1):18799. doi: 10.1038/s41598-024-69313-7.
The pressure-induced structural changes in the perovskite-type (ABO ) ferroelectric solid solution (1-x)Na Bi TiO -xBaTiO (NBT-xBT) at the morphotropic phase boundary (MPB) ( ) have been analyzed up to 12.3 GPa by single-crystal x-ray diffraction with synchrotron radiation. A pressure-induced phase transition takes place between 4.4 and 5.0 GPa, where the pseudocubic low-pressure phase transforms into an orthorhombic high-pressure phase with space group Pnma. The high-pressure phase is comprised of mixed BO tilts and anti-polar A-cation displacements, without exhibiting coherent off-centered shifts of the B-site Ti cations that can be detected by synchrotron x-ray diffraction. Our results reveal that at ambient pressure and room temperature the NBT- BT structure possesses anti-phase BO tilts with a relatively large correlation length and the same type of polar distortions as those present in pure NBT, but with strongly violated correlation length due to Ba -induced local elastic-stress fields. For the effect of Ba on the mesoscopic-scale structure is compensated by a mild external pressure of only 0.7 GPa, resulting in structural features resembling those of pure NBT at ambient conditions.
利用同步辐射单晶X射线衍射，对钙钛矿型（ABO₃）铁电固溶体（1-x）Na₀.₅Bi₀.₅TiO₃-xBaTiO₃（NBT-xBT）在准同型相界（MPB）（x = 0.08）处压力诱导的结构变化进行了分析，压力最高达到12.3 GPa。在4.4至5.0 GPa之间发生了压力诱导的相变，其中伪立方低压相转变为空间群为Pnma的正交高压相。高压相由混合的BO₆倾斜和反极A阳离子位移组成，未表现出能通过同步辐射X射线衍射检测到的B位Ti⁴⁺阳离子的相干偏心位移。我们的结果表明，在常压和室温下，NBT-0.08BT结构具有反相BO₆倾斜，其相关长度相对较大，并且具有与纯NBT中相同类型的极性畸变，但由于Ba²⁺诱导的局部弹性应力场，相关长度严重受损。对于x = 0.08，Ba对介观尺度结构的影响仅通过0.7 GPa的适度外部压力得到补偿，从而产生了与常压条件下纯NBT相似的结构特征。
