HfO2 99.9
Grade · default condition
Standard dense technical hafnia for crucibles, high-temperature insulators and refractory parts where thermal cycling through 1700 °C is avoided.
Values for the 99.9 condition
Other HfO2 tempers and conditions
HfO2 is listed in 4 conditions; see the grade overview at HfO2.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Plasma-spray / EB-PVD coating grade | Spray-dried or fused-and-crushed powder deposited as a porous, strain-tolerant thermal/environmental barrier layer on superalloys and C/C-SiC. | — | 25 | 0.1 | 550 HV | 1 W/m·K |
optical / electronic grade (evaporation material, high-k dielectric) | Pick for UV–IR high-refractive-index coatings, laser mirrors and gate-dielectric/ALD film work where trace metals and absorption must be minimal. | — | 120 | 0.1 | 850 HV | 2 W/m·K |
99.9DefaultThis page pressed & sintered monoclinic hafnia (technical grade) | Standard dense technical hafnia for crucibles, high-temperature insulators and refractory parts where thermal cycling through 1700 °C is avoided. | — | — | — | 800 HV | 2 W/m·K |
Yttria-stabilized hafnia | Choose when parts must be thermally cycled above 1700 °C — Y2O3 suppresses the monoclinic transformation and its damaging volume change. | — | — | — | 950 HV | 1 W/m·K |
What is HfO2 99.9?
HfO2 99.9 is HfO2 in the 99.9 grade — standard dense technical hafnia for crucibles, high-temperature insulators and refractory parts where thermal cycling through 1700 °C is avoided. The elastic modulus is 240 GPa (34.8 Msi). HfO2 99.9 has a density of 9.5 g/cm³ (0.343 lb/in³), heavier than 77% of ceramic grades. It melts at 2,758°C (4,996 °F).
Advantages
- High service temperature — 2,200°C (3,992 °F), better than 96% of ceramic grades
- Good corrosion resistance — 92/100, better than 88% of ceramic grades
Limitations
- High embodied carbon — 45 kg CO₂/kg, worse than 96% of ceramic grades
- Poor heat conductor — 1.7 W/m·K (0.982 BTU/hr·ft·°F), worse than 90% of ceramic grades
- Heavy — 9.5 g/cm³ (0.343 lb/in³), worse than 77% of ceramic grades
HfO2 99.9 properties
Typical room-temperature values for HfO2 99.9; 10 are specific to this condition. Other listed values are HfO2 reference data and may not represent this condition. Bars are the position among ceramic grades.
Physical4
HfO2 99.9 has a density of 9.5 g/cm³ (0.343 lb/in³), heavier than 77% of ceramic grades. It melts at 2,758°C (4,996 °F).
Mechanical10
The elastic modulus is 240 GPa (34.8 Msi).
Thermal5
HfO2 99.9 is rated for continuous service to 2,200°C (3,992 °F). It conducts heat at 1.7 W/m·K (0.982 BTU/hr·ft·°F), worse than 90% of ceramic grades. Thermal expansion is 5.8 µm/m·K (3.22 µin/in·°F).
Electrical5
HfO2 99.9 is an electrical insulator with a dielectric strength of 20 kV/mm (508 V/mil) and a resistivity of 1×10¹⁰ Ω·m.
Chemical & Environmental2
Corrosion resistance is excellent (92/100), better than 88% of ceramic grades.
Sustainability2
Producing a kilogram of HfO2 99.9 takes about 700 MJ of energy and emits 45 kg of CO₂ — more than 95% of ceramic grades.
Manufacturability3
HfO2 99.9's machinability is not recommended (8/100, better than 69% of ceramic grades).
Common Calculations2
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with HfO2 99.9
Is HfO2 easy to machine?
Green/bisque machining is the only economical route; fired parts need diamond grinding, lapping and ultrasonic/laser drilling, and the high density makes stock removal slow and costly.
Can HfO2 be welded?
Not weldable — join by active-metal brazing (Ti/Zr-bearing filler), glass sealing or mechanical clamping with matched-CTE metals.
Can HfO2 be formed, bent or molded?
Uniaxial/CIP pressing, slip casting or tape casting of fine powder, then sintering at 1600–1900 °C (often HIP or a Y2O3/CaO stabilizer); allow for large firing shrinkage and avoid crossing the 1700 °C phase transformation in unstabilized bodies.
What surface finishes work on HfO2?
Diamond lap and polish for optical or sealing faces; PVD/EB evaporation and ALD are the standard routes for thin high-k and high-index films.
HfO2 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 |
|---|---|---|
| ZrO2Zr is the natural chemical twin of Hf; excluded from the purity figure by most suppliers, nuclear grades specify <1 % | ≤ 2 | 0.3 |
| SiO2 | ≤ 0.05 | 0.01 |
| Al2O3 | ≤ 0.05 | 0.01 |
| Fe2O3 | ≤ 0.02 | 0.01 |
| TiO2 | ≤ 0.02 | 0.01 |
| Y2O38–12 mol % added only in the stabilized (YSH) variant | ≈ 0 | 0 |
| HfO2monoclinic (baddeleyite-type) hafnia; purity usually quoted on a Zr-free basis | ≥ 99.5 (balance) | — |
HfO2 99.9 — frequently asked
What is HfO2 99.9 used for?
HfO2 99.9 is typically used for ultra-high-temperature coatings, high-k gate dielectrics, thermal barrier layers and nuclear control rods. In short: highest-temperature oxide here; high-k dielectric source; dense and costly.
Is HfO2 99.9 easy to machine?
Not especially — machinability is rated not recommended (8/100, better than 69% of ceramic grades). Green/bisque machining is the only economical route; fired parts need diamond grinding, lapping and ultrasonic/laser drilling, and the high density makes stock removal slow and costly.
Can HfO2 99.9 be welded?
Not weldable — join by active-metal brazing (Ti/Zr-bearing filler), glass sealing or mechanical clamping with matched-CTE metals.
What surface finishes work on HfO2 99.9?
Diamond lap and polish for optical or sealing faces; PVD/EB evaporation and ALD are the standard routes for thin high-k and high-index films.
Can HfO2 99.9 be formed, bent or molded?
Uniaxial/CIP pressing, slip casting or tape casting of fine powder, then sintering at 1600–1900 °C (often HIP or a Y2O3/CaO stabilizer); allow for large firing shrinkage and avoid crossing the 1700 °C phase transformation in unstabilized bodies.
What is the maximum service temperature of HfO2 99.9?
HfO2 99.9 is rated for continuous use to about 2,200°C (3,992 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- Engineered Materials Handbook Vol. 4: Ceramics and Glasses — ASM International (1991)
- CRC Handbook of Chemistry and Physics — CRC Press (2020)
- NIST-JANAF Thermochemical Tables (HfO2) — NIST (1998)
- Phase Diagrams for Ceramists — HfO2–Y2O3 system — American Ceramic Society (1992)
- Hafnium oxide sputtering target / evaporation material data — Materion (2023)
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.