我们提出了一种高灵敏度的方法，可以测量绝缘材料在有限频率下的非线性介电极化率。本文介绍了一种用于研究过冷液体在0.05 Hz < f < 30000 Hz频率范围内动态非均匀性的介电谱仪。它依赖于对从电容器流出的电流的三次谐波分量的测量。我们首先表明，标准的实验室电子（放大器和电压源）的非线性导致限制的三次谐波测量，排除达到我们的物理目标所需的水平，三次谐波的基本信号比约7个数量级低于1。我们表明，达到这样的灵敏度需要一种方法，能够摆脱的非线性贡献的测量设备（锁定放大器）和激励电压源。使用两个源的电桥仅满足这两个要求中的第一个，但允许测量源的非线性。我们的最终方法是基于一个桥，其特征在于由不同的介电层厚度的两个平面电容器。它摆脱了源和放大器的非线性，因为尽管电容器阻抗的频率依赖性很强，但它在任何频率下都是平衡的。我们提出了第一次测量的物理非线性响应，使用我们的方法。两个扩展的方法建议。
英文摘要：
We present a high sensitivity method allowing the measurement of the non linear dielectric susceptibility of an insulating material at finite frequency. It has been developped for the study of dynamic heterogeneities in supercooled liquids using dielectric spectroscopy at frequencies 0.05 Hz < f < 30000 Hz . It relies on the measurement of the third harmonics component of the current flowing out of a capacitor. We first show that standard laboratory electronics (amplifiers and voltage sources) nonlinearities lead to limits on the third harmonics measurements that preclude reaching the level needed by our physical goal, a ratio of the third harmonics to the fundamental signal about 7 orders of magnitude lower than 1. We show that reaching such a sensitivity needs a method able to get rid of the nonlinear contributions both of the measuring device (lock-in amplifier) and of the excitation voltage source. A bridge using two sources fulfills only the first of these two requirements, but allows to measure the nonlinearities of the sources. Our final method is based on a bridge with two plane capacitors characterized by different dielectric layer thicknesses. It gets rid of the source and amplifier nonlinearities because in spite of a strong frequency dependence of the capacitors impedance, it is equilibrated at any frequency. We present the first measurements of the physical nonlinear response using our method. Two extensions of the method are suggested.
Subcoercive-field dielectric response of $0.5(\text{Ba}_{0.7}\text{Ca}_{0.3}\text{TiO}_{3})-0.5(\text{BaZr}_{0.2}\text{Ti}_{0.8}\text{O}_{3})$ thin film: peculiar third harmonic signature of phase transitions and residual ferroelectricity
History-dependent and frequency-dependent dielectric nonlinearities induced by polar nanoregions in a thin film of 0.5 ( Ba 0.7 Ca 0.3 TiO 3 ) -- 0.5 ( BaZr 0.2 Ti 0.8 O 3 )
