The Space Charge Measurement by Pulsed Electroacoustic Method up to 200 ^∘C

In this letter, an improved pulsed electroacoustic (PEA) device is modified to test the space charge distributions in polytetrafluoroethylene (PTFE) at high temperatures (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$90~^{\circ }$ </tex-math></inline-formula>C–<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$200~^{\circ }$ </tex-math></inline-formula>C). The LiNbO3 sensor and temperature controller suitable for high temperature’s measurement are designed. The voltage protocol is composed of electric field application from 30 to 50 kV/mm in a stepwise manner with 30-min polarization and depolarization. It shows that LiNbO3 can be used as a sensor material to test space charge at high temperatures up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$200~^{\circ }$ </tex-math></inline-formula>C. The PTFE has no obvious charge injection below <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$150~^{\circ }$ </tex-math></inline-formula>C. Above <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$150~^{\circ }$ </tex-math></inline-formula>C, the anode injects a large amount of positive charge, which migrates to the cathode in the form of space charge packets. It is expected that this PEA measurement technique is helpful to develop insulating materials for high temperatures.