ZnO Varistor HG
Grade
HG = high-gradient fine-grain ceramic
Pick where volume must be minimized — GIS/HVDC arresters, compact surge modules; fine grains raise the switching gradient but demand tight sintering control to keep energy handling.
Values for the HG condition
Other ZnO Varistor tempers and conditions
ZnO Varistor is listed in 3 conditions; see the grade overview at ZnO Varistor.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Low-voltage varistor ceramic | Pick for low-voltage MOVs and multilayer chip varistors protecting 3–60 V electronics; coarse ZnO grains give low varistor voltage but very high capacitance. | — | 48 | 0.05 | 370 HV | 20 W/m·K |
High-energy arrester block | Pick for MV/HV metal-oxide surge arresters (IEC 60099-4, GB/T 11032): large-diameter blocks optimized for energy absorption and long-term ageing stability rather than compactness. | — | 58 | 0.05 | 410 HV | 20 W/m·K |
HGThis page High-gradient fine-grain ceramic | Pick where volume must be minimized — GIS/HVDC arresters, compact surge modules; fine grains raise the switching gradient but demand tight sintering control to keep energy handling. | — | 65 | 0.05 | 450 HV | 15 W/m·K |
What is ZnO Varistor HG?
ZnO Varistor HG is ZnO Varistor in the HG grade — pick where volume must be minimized — GIS/HVDC arresters, compact surge modules; fine grains raise the switching gradient but demand tight sintering control to keep energy handling. The elastic modulus is 125 GPa (18.1 Msi). ZnO Varistor HG has a density of 5.65 g/cm³ (0.204 lb/in³), heavier than 57% of ceramic grades. It melts at 1,975°C (3,587 °F).
Advantages
- Low embodied carbon — 3.6 kg CO₂/kg, better than 80% of ceramic grades
Limitations
- Limited service temperature — 150°C (302 °F), worse than 90% of ceramic grades
- Needs corrosion protection — 50/100, worse than 83% of ceramic grades
- Hard to polish — 60/100, worse than 79% of ceramic grades
ZnO Varistor HG properties
Typical room-temperature values for ZnO Varistor HG; 18 are specific to this condition. Other listed values are ZnO Varistor reference data and may not represent this condition. Bars are the position among ceramic grades.
Physical3
ZnO Varistor HG has a density of 5.65 g/cm³ (0.204 lb/in³), heavier than 57% of ceramic grades. It melts at 1,975°C (3,587 °F).
Mechanical9
The elastic modulus is 125 GPa (18.1 Msi).
Thermal5
ZnO Varistor HG is rated for continuous service to 150°C (302 °F). It conducts heat at 15 W/m·K (8.67 BTU/hr·ft·°F), worse than 57% of ceramic grades. Thermal expansion is 6.5 µm/m·K (3.61 µin/in·°F).
Electrical5
ZnO Varistor HG is an electrical insulator with a dielectric strength of 0.45 kV/mm (11.4 V/mil) and a resistivity of 1×10⁹ Ω·m.
Chemical & Environmental2
Corrosion resistance is fair (50/100), worse than 83% of ceramic grades.
Sustainability4
Producing a kilogram of ZnO Varistor HG takes about 55 MJ of energy and emits 3.6 kg of CO₂ — less than 78% of ceramic grades. Typical recycled content is 5%.
Manufacturability3
ZnO Varistor HG's machinability is not recommended (8/100, better than 69% of ceramic grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with ZnO Varistor HG
Is ZnO Varistor easy to machine?
Green bodies are readily machined/punched; fired ceramic requires diamond grinding or lapping — barrel/edge grinding before side passivation is the normal finishing step.
Can ZnO Varistor be welded?
Not weldable; blocks are joined to metal end caps by flame/arc-sprayed Al electrodes, solder or conductive adhesive, and stacked with spring compression in the arrester housing.
Can ZnO Varistor be formed, bent or molded?
Spray-dried doped ZnO powder is uniaxially or isostatically pressed (or tape cast/laminated for chip varistors), binder-burned at ~500 °C and liquid-phase sintered at 1050–1250 °C with a controlled slow cool to develop grain-boundary barriers.
What surface finishes work on ZnO Varistor?
Side surfaces are coated with high-resistivity glass/ceramic passivation or silicone/epoxy to suppress flashover; flat faces are ground then Al-metallized (arc spray) for ohmic contact.
ZnO Varistor chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Bi2O3grain-boundary liquid/barrier former (Pr6O11 in some formulas) | 0.3 – 2.5 | 1 |
| Sb2O3forms spinel phase, inhibits grain growth | 0.3 – 2 | 1.2 |
| CoOraises nonlinearity coefficient α | 0.2 – 1.5 | 0.6 |
| MnO2deep-level acceptor, improves the barrier | 0.1 – 1 | 0.4 |
| Cr2O3aging resistance | 0.1 – 1 | 0.3 |
| NiOaging resistance / lower leakage current | 0.1 – 1.5 | 0.5 |
| SiO2controls grain size; high content in high-gradient formulas | 0 – 1.5 | 0.5 |
| Al2O3donor dopant, lowers grain resistivity | 0 – 0.05 | 0.01 |
| B2O3 / glass fritside insulating glaze/flux (process dependent) | 0 – 1 | 0.2 |
| ZnOmain phase, semiconducting grains | ≥ 88 (balance) | — |
ZnO Varistor HG — frequently asked
What is ZnO Varistor HG used for?
ZnO Varistor HG is typically used for surge arresters, MOV transient suppressors and power line protection. In short: non-linear surge protection ceramic; basis of metal-oxide varistors; grain-boundary functional oxide.
Is ZnO Varistor HG easy to machine?
Not especially — machinability is rated not recommended (8/100, better than 69% of ceramic grades). Green bodies are readily machined/punched; fired ceramic requires diamond grinding or lapping — barrel/edge grinding before side passivation is the normal finishing step.
Can ZnO Varistor HG be welded?
Not weldable; blocks are joined to metal end caps by flame/arc-sprayed Al electrodes, solder or conductive adhesive, and stacked with spring compression in the arrester housing.
What surface finishes work on ZnO Varistor HG?
Side surfaces are coated with high-resistivity glass/ceramic passivation or silicone/epoxy to suppress flashover; flat faces are ground then Al-metallized (arc spray) for ohmic contact.
Can ZnO Varistor HG be formed, bent or molded?
Spray-dried doped ZnO powder is uniaxially or isostatically pressed (or tape cast/laminated for chip varistors), binder-burned at ~500 °C and liquid-phase sintered at 1050–1250 °C with a controlled slow cool to develop grain-boundary barriers.
What is the maximum service temperature of ZnO Varistor HG?
ZnO Varistor HG is rated for continuous use to about 150°C (302 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- IEC 61051-1/-2 Varistors for use in electronic equipment — IEC (2018)
- IEC 60099-4 Surge arresters — Metal-oxide surge arresters without gaps for a.c. systems — IEC (2014)
- Engineered Materials Handbook Vol.4: Ceramics and Glasses — ASM International (1991)
- Varistor Ceramics — review of ZnO grain-boundary devices (J. Am. Ceram. Soc.) — American Ceramic Society (1999)
- EPCOS/TDK Metal Oxide Varistors — general technical information — TDK Electronics (2023)
- Littelfuse Varistor Products — MOV application notes — Littelfuse (2022)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.