Resistance of Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 under high voltage microsecond pulse induced breakdown

Abstract

Ferroelectric ceramics have been widely used in lots of fields, such as mechanical-electric transducer, ferroelectric memory, and energy storage devices. The dielectric breakdown process of ferroelectric ceramic has received much attention for years, due to the fact that this issue is critical in many electrical applications. Though great efforts have been made, the mechanism of dielectric breakdown is still under debate. The reason is that the electrical breakdown is a complex process related to electrical, thermal, and light effects. In the present work, we investigate the breakdown process of Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3(PZT95/5) ceramic, which is a kind of typical ferroelectric ceramic working in the high voltage environments. The high voltage pulse generator is used in the breakdown experiments to apply a square pulsed voltage with an amplitude of 10 kV and a width of 7 s. The resistivity change in the breakdown process is recorded by the high-frequency oscillograph in nano-second. The results show that there are two different breakdown types for our sample, i.e. body-breakdown and flashover. To better understand the breakdown mechanism of the PZT95/5 ceramic, the formation of the conductive channel in ceramic in the process is investigated by comparing the resistivity development in body-breakdown and flashover processes. The development of the conductive channel formation can be divided into three steps in body-breakdown. In the first step that lasts for the first 40 ns of breakdown, the conductive channel starts forming, with the equivalent resistance sharply decreasing to about 105 in the mean time. Then, i.e. in the second step, conductive path grows into a stable one with the equivalent resistance decreasing to the magneitude of about 102 . The resistance decreases slowly to about 130 in the third step, which means that the conductive channel is completely formed. The channel formation of flashover can also be divided into three steps. The first step is similar to that of body-breakdown, with the equivalent resistance decreasing to about 105 in about 40 ns. In the second step of flashover, the conductive path keeps growing into a stable one with the equivalent resistance decreasing to 102 , but with a different resistance changing rate from that in body-breakdown, and the resistance decreases slowly to about 20 in the end. Different behavior between the body-breakdown and the surface flashover can be explained by different carrier densities on the conductive paths in the two breakdown processes. In the body-breakdown, the carrier density in the conductive channel is higher than that in the surface flashover, which improves the electron transfer and reduces the resistance. This may explain the reason why the channel formation in body-breakdown is faster than in flashover. This study is helpful for further materials design and applications.