1. SiC-based Boundary Layer Capacitors Rui Zhang Zhengzhou University zhangray@zzu.edu.cn

2. Outlines 1. Backgrounds for SiC-based BLCs 2. Preparation of the SiC-based BLCs 3. Characteristics of the SiC-based BLCs 4. Summary

3. 1. Backgrounds for SiC-based BLCs Traditionally, SiC is not suitable for capacitor applications Ferroelectrics with perovskite structure BaTiO 3 -1vol%SiC   300,000 La-PbTiO 3   450,000 compounds  SiC10 BaTiO310000 SrTiO3320 PbTiO3350 PbZrO 3 110 Pb(Mg 1/3 Nb 2/3 )O 3 15000 Pb(Ni 1/3 Nb 2/3 )O 3 4000 Pb(Zn 1/3 Nb 2/3 )O 3 22000 Pb(Fe 1/2 Nb 1/2 )O 3 12000 Pb(Fe 2/3 W 1/3 )O 3 9000 PFN-PFW21000 If we modify grain boundary of SiC Composites, How about the dielectric properties?

4. 2. Preparation of the SiC-based BLCs Semi-conductive SiC particles Al 2 O 3 -MgO-SiO 2 Mixing Hot Pressing Microstructure characterization Dielectric properties measurement Impedance detection

5. 3. Characteristics of the SiC-based BLCs Microstructure Width of grain boundary  200 nm Amorphous grain boundary Insulation phase

6. Nano grains of new phases Increasing the interface area

7. Dielectric properties At 500 o C,  increases sharply At 590 – 730 o C Higher temperature increases the conductivity of samplessamples at 700 o C

8. Complex impedance R decreases from 1.4 M  to 0.08 M  at 190 o C and 500 o C, respectively Perfect semi-circle at 190 o CTail appears at low frequency at 500 o C Space charge polarization phenomena

9. Space charge polarization Higher T leads to much lower R Tails at low f grow with T Highest space charge polarization appears at around 700 o Cappears More charge carriers are generated in SiC improving the C and apparent  Indicating enhancing space charge behavior It is the space charge behavior that gives rise to the extremely high  Charge carriers accumulate at the insulation boundary to form space charge region

10. The space charge behavior also determines the lowering tan lowering tan  Maximum tan  occurs at the initial T of space charge polarization

11. Surface potential induction Atomic Force Microscope system Sub sequential DC pulse at: 5 V, 10 V, 0 V, - 5 V, - 10 V

12. (a)(b)(c) Potential image 5 V 10 V0 V Space charge behavior does appear for the SiC-based capacitors

13. 4. Summary Space charge behavior appears with temperature for the SiC-based BLCs The space charge behavior leads to the extremely high , and lowers the tan 

14. Thank you for your attention