0.65[Pb（Ni_1/3Nb_2/3）O_3]-0.35PbTiO_3陶瓷低温下的介电弛豫和相变
Dielectric Relaxation and Phase Transition at Cryogenic Temperatures in 0.65[Pb(Ni_1/3Nb_2/3)O_3]-0.35PbTiO_3 Ceramics
摘要：
0.65[Pb（Ni_（1/3）Nb_（2/3））O_3]-0.35 PbTiO_3陶瓷在90 - 470 K温度范围内的介电测量表明，在350 K附近出现弛豫铁电转变，Vogel-Fulcher凝固温度为338 K，室温下出现四方晶系结构的非遍历弛豫铁电相。该非遍历相在低温下重新进入弛豫状态，如在160 K附近的介电常数的虚部中出现频率依赖性异常所证明的，类似于在其他弛豫铁电基准同型相界陶瓷中报道的那些。极化弛豫时间为160 K异常也遵循Vogel-Fulcher型温度依赖性。温度相关的磁化测量表明，这种低温异常与任何磁转变无关。弹性模量和低温X-射线衍射（XRD）测量揭示了在225 K附近的四斜晶系到单斜晶系的相变。有人认为，低温介电色散约160 K的结果从冻结的介观共形小型化单斜畴内形成的母四畴低于结构相变温度225 K。
英文摘要：
Dielectric measurements on 0.65[Pb(Ni_1/3Nb_2/3)O_3]-0.35PbTiO_3 ceramic in the temperature range 90K to 470K shows a relaxor ferroelectric transition around 350K with a Vogel-Fulcher freezing temperature of 338K and appearance of a non-ergodic relaxor ferroelectric phase of tetragonal structure at room temperature. This non-ergodic phase reenters into the relaxor state at low temperatures as evidenced by the appearance of a frequency dependent anomaly in the imaginary part of the dielectric constant around 160K, similar to those reported in other relaxor ferroelectric based morphotropic phase boundary ceramics. The polarization relaxation time for the 160K anomaly also follows Vogel-Fulcher type temperature dependence. Temperature dependent magnetization measurements show that this low temperature anomaly is not linked with any magnetic transition. Elastic modulus and low temperature x-ray diffraction (XRD) measurements reveal a tetragonal to monoclinic phase transition around 225K. It is argued that the low temperature dielectric dispersion around 160K results from the freezing of mesoscopic conformally miniaturized monoclinic domains formed inside the parent tetragonal domains below the structural phase transition temperature of 225K.
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