The abnormal improved dielectric in La-doped relaxor ferroelectric PNN-PHT

Relaxor ferroelectrics are complex materials with properties that are remarkably different from traditional ferroelectrics, and they have the ability to probe frequency-dependent dielectric susceptibility. However, the empirical laws developed for traditional ferroelectrics also apply to relaxor ferroelectrics. Here we report an abnormally improved dielectricity of the La-doped relaxor ferroelectric 0.4PNN-0.6PHT, which does not linearly vary with the piezoelectric coefficient, as it is expected. A mesoscale mechanism is proposed to explain the origin of the improved dielectric response of 0.4PNN-0.6PHT, in which the alignment of polar nano regions facilitates the polarization response to the external field. This mechanism demonstrates the critical role of polarization fluctuation for the macroscopic properties of 0.4PNN-0.6PHT.