Polar phonons and far-infrared amplitudon in Sr2Nb2O7
Polar phonons and far-infrared amplitudon in Sr2Nb2O7
复制标题
Sr2Nb2O7 中的极性声子和远红外振幅
DOI：
10.1088/0953-8984/13/12/307
复制
发表时间：
2001
期刊：
影响因子：
--
通讯作者：
J. Petzelt
中科院分区：
文献类型：
--
作者：
E. Buixaderas;S. Kamba;J. Petzelt
在10-550 K温度范围内对Sr_2Nb_2O_7单晶的远红外偏振反射率和透射率进行了测量||a和E|| c极化。在随后的顺电-铁电-绝缘-单斜相和因素组分析以及模式的相关性的布里渊区的中心模式进行了分析。在T_c = 1613 K以下的拉曼谱中发现了铁电A1软模，||c偏振红外光谱。在无公度相中观察到一个软化到Ti = 488 K的振幅。在冷却的振幅反交叉硬激发附近33 cm-1位于dispersiations，然后，在约100 K，也铁电软模式。没有证据表明，较早提出的倍增的单位细胞低于相变在T0 = 117 K。忽略小体积的位错，我们建议Pb 11-C2 S空间群（Z = 4）的单斜相低于T0。
Polarized far-infrared reflectivity and transmission measurements of an Sr2Nb2O7 single crystal were performed in the temperature interval 10-550 K for the E||a and E||c polarizations. Modes at the centre of the Brillouin zone were analysed in the subsequent paraelectric-ferroelectric-incommensurate-monoclinic phases and the factor group analysis together with the correlation of the modes is presented. The ferroelectric A1 soft mode revealed in Raman spectra below Tc = 1613 K was found in the E||c polarized infrared spectra. An amplitudon which softens to Ti = 488 K was observed in the incommensurate phase. On cooling the amplitudon anti-crosses a hard excitation near 33 cm-1 located in discommensurations and then, at about 100 K, also the ferroelectric soft mode. No evidence was found for the earlier suggested multiplication of the unit cell below the phase transition at T0 = 117 K. Neglecting the small volume of discommensurations, we suggest the Pb11-C2S space group (Z = 4) for the monoclinic phase below T0.
不通约结构K_xRhO_2晶体的高分辨率电子显微镜
DOI：
--
发表时间：
2009
期刊：
Phil.Mag. 89
影响因子：
--
作者：
K.Yubuta;S.Shibasaki;I.Terasaki;T.Kajitani
通讯作者：
T.Kajitani