Local structure investigation of the ferroelectric phase transition of BaSn0.1Ti0.9O3 using neutron pair distribution function

Local structural distortions in BaTiO3-solid solutions, where Ti site is substituted by isovalent Sn cation Ba(Sn,Ti)O3, are characterized not by oxygen tilts but the existence of different Ti(Sn)-O bonds, leading to different polar orders, from ferroelectrics to relaxors. For the ferroelectric BaSn0.1Ti0.9O3 compound, we carried out synchrotron radiation diffraction experiments to investigate the structural sequence through the ferroelectric transition happening at 300K, but extending through 20K, from the low temperature ferroelectric R3m phase to the high temperature paraelectric Pm-3m one. Our experiments using synchrotron pair distribution function did not allow us to determine any local structure change through the ferroelectric transition. Neutron scattering pair distribution function will allow us quantifying local disorder and symmetry, identifying the role played by Sn and Ti.

钛酸钡固溶体中，钛位点被等价价态的锡阳离子取代后形成Ba(Sn,Ti)O₃，其局域结构畸变并非源于氧倾斜，而是不同Ti(Sn)-氧键的存在所导致，进而催生了从铁电体到弛豫铁电体的多样极性序。针对铁电组分BaSn₀.₁Ti₀.₉O₃化合物，我们开展了同步辐射衍射实验，以探究其在300K发生的铁电相变过程中的结构演变路径，实验温度覆盖范围从20K的低温铁电R3m相至高温顺电Pm-3m相。我们采用同步辐射对分布函数开展的实验，未能明确观测到铁电相变过程中的局域结构变化。后续借助中子散射对分布函数实验，我们将能够定量表征局域无序与对称性，并厘清锡与钛在体系中所发挥的作用。