Institute of Physics ASCR, Na Slovance 2, 182 21, Prague 8, Czech Republic.
J Phys Condens Matter. 2011 Jan 19;23(2):025904. doi: 10.1088/0953-8984/23/2/025904. Epub 2010 Dec 16.
Dielectric properties of Eu(0.5)Ba(0.5)TiO(3) ceramics were investigated between 10 and 300 K in the frequency range of 1 MHz-100 THz. Permittivity exhibits a strong peak near the ferroelectric phase transition at 215 K. This is mainly due to softening of the lowest frequency polar phonon revealed in THz and infrared spectra. Dielectric relaxation was observed also below the ferroelectric soft mode frequency in the whole investigated temperature region, but it is probably caused by some defects such as Eu(3 + ) cations or oxygen vacancies. This implies that the ferroelectric phase transition has predominantly a displacive character. Raman scattering spectra revealed a lowering of crystal symmetry in the ferroelectric phase and XRD analysis indicated orthorhombic A2mm symmetry below 215 K. The magnetic measurements performed at various frequencies in the field cooled and field heating regime after cooling in zero magnetic fields excluded spin glass behavior and proved an antiferromagnetic order below 1.9 K in Eu(0.5)Ba(0.5)TiO(3).
Eu(0.5)Ba(0.5)TiO(3)陶瓷的介电性能在 10 至 300 K 的温度范围内和 1 MHz-100 THz 的频率范围内进行了研究。介电常数在 215 K 的铁电相转变附近表现出强烈的峰值。这主要归因于太赫兹和红外光谱中揭示的最低频率极性声子的软化。在整个研究的温度范围内，也观察到低于铁电软模频率的介电弛豫，但它可能是由 Eu(3+)阳离子或氧空位等缺陷引起的。这意味着铁电相转变主要具有位移特征。拉曼散射光谱显示在铁电相中的晶体对称性降低，XRD 分析表明在 215 K 以下为正交 A2mm 对称。在零磁场冷却后，在磁场冷却和磁场加热两种状态下，在不同频率下进行的磁测量排除了自旋玻璃行为，并证明了 Eu(0.5)Ba(0.5)TiO(3)在 1.9 K 以下存在反铁磁序。
