Normalized dielectric constants for as-deposited samples under different frequencies. Frequencies: 100 Hz, 1 kHz, 10 kHz, 100 kHz, and 1 MHz. The grain size value for the samples of the different deposition temperatures (Figure 1) is denoted with respective symbols (diamond, square, star, triangle, and round). The Cole-Davidson fitting for each curve is represented by a solid line. The sample of 8.83 nm has the most severe dielectric relaxation. However, in comparing the samples of 6.13 and 23.62 nm, the larger-grain-size sample is proved to have better performance on dielectric relaxation. Similarly, normalized dielectric constants for the Nd-doped PNZT samples  are shown in the inset under various frequencies (100 Hz, 1 kHz, 10 kHz, 100 kHz, and 1 MHz) as supporting evidence. The grain size value for each sample is denoted with respective symbols (diamond, square, star, triangle, round, and cross). It is obvious that the deteriorative degree of dielectric relaxation increases from 12.1 nm, reaches the peak at 22.5 nm, and then is relieved much to a better situation. The last sample with the grain size of 25 nm is shown to have dielectric relaxation superior to the sample of 12.1 nm.
Zhao et al. Nanoscale Research Letters 2013 8:172 doi:10.1186/1556-276X-8-172