Study on effect of temperature gradient of TSDC measuring system

Thermally stimulated depolarization current (TSDC) measurement is a useful method to determine the charges transportation and trap levels in dielectric. By testing temperature differences and polyester (PET) films' TSDC curves of electrodes with different size and structure, this paper analysis the influence of temperature gradient on the test. The result shows that asymmetric electrode structure can result in uneven heating condition of the specimen, and then produces a temperature gradient in specimen's thickness direction, a complete TSDC curve consists of two distinct peaks named α peak and ρ peak. Temperature gradient has a greater impact on ρ peak which is caused by trapped charge in PET films, while has less impact on the α peak's position which is caused by dipole. Under a certain temperature gradient, the ρ peak which is caused by trapped charges will move forward to a lower temperature and may have a reverse peak in the negative direction, while the position of α peak that is caused by dipole does not change obviously. These factors above cause a overlap of α peak and ρ peak, which will influence the resolution and reliability of TSDC test.