铁电共聚物VDF／TrFE的低温低频介电松弛

Dielectric Relaxation of VDF/TrFE Copolymer Ferroelectric at Low Temperature and Frequency

在低温低频下用介电松弛方法研究了液氮淬火、熔融慢冷和热处理结晶铁电共聚物ＶＤＦ（７３）／ＴｒＦＥ（２７）的分子运动特征。随结晶度升高，居里点温度降低，铁电－顺电相变区的介电常数增大。室温以下共聚物的频率谱由低频和高频两部分组成。低频部由非晶区被冻结分子链段的微布朗运动贡献；高频部则由晶区和非晶区分子链段较小尺度的局域运动产生。由两个Ｃｏｌｅ－Ｃｏｌｅ函数对频率谱进行分峰拟合并根据ＷＬＦ方程和Ａｒｒｈｅｎｉｕｓ表达式计算得到的共聚物玻璃化转变温度为－３７℃，局域松弛活化能为４８．８ｋＪ／ｍｏｌ。

The characteristics of molecular motion of the vinylidene fluoride ( 73)/trifluoroethylene(27)copolymer ferroelectric have been investigated by dielectric relaxation measure-ments at low temperatures and low frequencies. With increase of the crystallinity of thecopolymer, the Curie-point temperature Tc decreased and the dielectric constant increased inthe region of ferroelectric-paraelectric phase transition. The frequency spectra of the copoly-mers below room temperature consisted of a low-frequency part ascribed to the micro-Brown-ian motion of molecular segments in the noncrystalline regions and a high-frequency part des-ignated as the local motions of small-scale segments. The T_g(=-37℃) and △H(=48. 8kJ/mol)of copolymers were obtained from the fitted results using two Cole-Cole functions andcalculation with WLF equation and Arrhenius formula respectively.