Views: 0 Author: Site Editor Publish Time: 2025-07-11 Origin: Site
Metal Oxide Varistors (MOVs), serving as the core components of Surge Protective Devices (SPDs), critically determine overvoltage protection performance in power systems and electronic equipment. With expanding frequency-domain requirements (from power frequency to MHz range) in renewable energy integration, high-speed railways, and 5G base stations, conventional MOV microstructural designs face significant challenges. This study focuses on microstructural optimization of ZnO-Bi₂O₃-based MOVs, proposing a multi-scale strategy to dramatically improve wide-frequency surge tolerance.
- Rare-earth oxide doping (Pr₆O₁₁, La₂O₃) adjusts barrier height (0.8→1.2 eV), boosting energy absorption capacity for low-frequency high-current surges (8/20μs) by 35%.
- Gradient sintering (900℃→1200℃) inhibits Bi segregation, forming continuous grain boundary phases and reducing residual voltage ratio (1.65→1.52).
- 0.5wt% Al₂O₃ nanoparticles (50nm) fill inter-granular voids, reducing microdefects and increasing partial discharge inception voltage at 1MHz by 28%.
- In-situ generated Zn₂SiO₄ spinel phase enhances mechanical strength, maintaining leakage current <5μA after 10kA 8/20μs impulse.
- Pore-forming agent (starch) gradient design (3-7vol%) constructs multi-scale pores (0.5μm micropores/20μm macropores), optimizing thermal dissipation efficiency at MHz frequencies (ΔT<15℃@100V/μs).
| Test Condition | Conventional MOV | Novel MOV | Improvement |
| 8/20μs 100kA | Failure | Pass 20 shots | |
| 10/350μs 40kA | 400kJ tolerated | 650kJ tolerated | +62.5% |
| 1MHz 10kV/μs | Residual ratio>2.0 | Ratio 1.75 | -12.5% |
Deployed in critical scenarios:
- HVDC Transmission: Withstands commutation overvoltage (0.1-100kHz)
- Data Centers: Protects against ns-level ESD events (>30kV/ns)
- Wind Power Converters: Passes 10kA 8/20μs + 2kV 1MHz composite waveform tests
This research resolves the inherent conflict in MOV wide-frequency protection—balancing low-frequency energy handling and high-frequency response—through multi-dimensional microstructural synergy. Future work will explore Atomic Layer Deposition (ALD) surface modification for GHz-range applications.
