KNN PURE
Grade
PURE = undoped (K0.5Na0.5)NbO3, conventional air sintering
Use the undoped, conventionally air-sintered baseline when the highest Curie temperature (~410 °C) or an academic reference matters; piezoelectric response and density are lower.
Values for the PURE condition
Other KNN tempers and conditions
KNN is listed in 5 conditions; see the grade overview at KNN.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
PUREThis page Undoped (K0.5Na0.5)NbO3, conventional air sintering | Use the undoped, conventionally air-sintered baseline when the highest Curie temperature (~410 °C) or an academic reference matters; piezoelectric response and density are lower. | — | — | — | 330 HV | 2 W/m·K |
Textured (templated grain growth) <001> KNN | Choose textured <001> material grown from NaNbO3 platelet templates when piezoelectric constants must come closest to soft PZT; cost and process complexity are the highest of the family. | — | — | — | 380 HV | — |
LTSDefault Li/Ta/Sb-modified soft KNN | Choose the Li/Ta/Sb-modified soft composition, with its phase boundary shifted near room temperature, for the highest piezoelectric and dielectric response in buzzers, atomizer discs and sensors. | — | — | — | 400 HV | 3 W/m·K |
CuO/Mn-doped hard KNN for high-power resonators | Pick the acceptor-doped CuO/Mn hard type for high mechanical quality factor Qm and low loss under continuous high-power drive, such as ultrasonic welding horns and cleaning transducers. | — | — | — | 420 HV | — |
HP/SPS | Use the hot-pressed or spark-plasma-sintered near-fully-dense route to suppress alkali volatilization and get the best strength, insulation and consistency in thin elements and high-field drive. | — | — | — | 460 HV | 3 W/m·K |
What is KNN PURE?
KNN PURE is KNN in the PURE grade — use the undoped, conventionally air-sintered baseline when the highest Curie temperature (~410 °C) or an academic reference matters; piezoelectric response and density are lower. The elastic modulus is 95 GPa (13.8 Msi). KNN PURE has a density of 4.25 g/cm³ (0.154 lb/in³), lighter than 56% of ceramic grades. It melts at 1,140°C (2,084 °F). LTS is the default condition FabDigit quotes; PURE is available on request or by drawing note.
Limitations
- Low fracture toughness — 0.85 MPa·√m (0.774 ksi·√in), worse than 98% of ceramic grades
- Poor heat conductor — 2 W/m·K (1.16 BTU/hr·ft·°F), worse than 87% of ceramic grades
- Limited service temperature — 200°C (392 °F), worse than 84% of ceramic grades
- Needs corrosion protection — 55/100, worse than 77% of ceramic grades
- Low stiffness — 95 GPa (13.8 Msi), worse than 75% of ceramic grades
KNN PURE properties
Typical room-temperature values for KNN PURE; 14 are specific to this condition. Other listed values are KNN reference data and may not represent this condition. Bars are the position among ceramic grades.
Physical4
KNN PURE has a density of 4.25 g/cm³ (0.154 lb/in³), lighter than 56% of ceramic grades. It melts at 1,140°C (2,084 °F).
Mechanical9
The elastic modulus is 95 GPa (13.8 Msi).
Thermal5
KNN PURE is rated for continuous service to 200°C (392 °F). It conducts heat at 2 W/m·K (1.16 BTU/hr·ft·°F), worse than 87% of ceramic grades. Thermal expansion is 7 µm/m·K (3.89 µin/in·°F).
Electrical5
KNN PURE is an electrical insulator with a dielectric strength of 6 kV/mm (152.4 V/mil) and a resistivity of 1×10⁸ Ω·m.
Chemical & Environmental2
Corrosion resistance is good (55/100), worse than 77% of ceramic grades.
Sustainability4
Producing a kilogram of KNN PURE takes about 160 MJ of energy and emits 11 kg of CO₂ — more than 59% of ceramic grades. Typical recycled content is 0%.
Manufacturability3
KNN PURE'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 KNN PURE
Is KNN easy to machine?
After firing, only diamond grinding, ultrasonic drilling or laser cutting is possible; machining in the green or bisque state is by far the cheapest route. Anneal after grinding to remove surface residual stress before poling.
Can KNN be welded?
The ceramic is not weldable. Metal connection is made through fired silver-paste electrodes followed by soft soldering below 250 °C to avoid depoling, or by conductive adhesive.
Can KNN be formed, bent or molded?
Dry pressing, cold isostatic pressing and tape casting are all usable. The sintering window is narrow (about ±20 °C), so fire in sealed saggars with excess alkali in the batch to compensate K/Na volatilisation, otherwise second phases and abnormal grain growth appear.
What surface finishes work on KNN?
Screen-print and fire silver electrodes at roughly 700–800 °C, or sputter Cr/Au. Pole at 2–4 kV/mm in silicone oil at 80–120 °C and age 24 h; finished parts need moisture-barrier packaging.
KNN 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 |
|---|---|---|
| Nbadded as Nb2O5; partly replaced by Ta/Sb in modified grades | 50 – 55 | 54 |
| Kfrom K2CO3; volatile in sintering, added in excess to compensate | 10 – 12 | 11.4 |
| Naintroduced as Na2CO3 | 6 – 7.5 | 6.7 |
| LiA-site dopant in modified (LTS) grades, ~3–6 mol% | 0 – 0.5 | 0.15 |
| TaB-site substitution for Nb in modified grades, ~10–20 mol% | 0 – 12 | 6 |
| SbB-site substitution in modified grades, ~3–7 mol% | 0 – 4 | 1.5 |
| Ooxygen site of perovskite ABO3, ~28 wt% | balance | — |
KNN PURE — frequently asked
What is KNN PURE used for?
KNN PURE is typically used for lead-free piezo actuators, lead-free sensors and green electronics components. In short: lead-free PZT alternative; narrow sintering window; lower density than PZT.
Is KNN PURE easy to machine?
Not especially — machinability is rated not recommended (8/100, better than 69% of ceramic grades). After firing, only diamond grinding, ultrasonic drilling or laser cutting is possible; machining in the green or bisque state is by far the cheapest route. Anneal after grinding to remove surface residual stress before poling.
Can KNN PURE be welded?
The ceramic is not weldable. Metal connection is made through fired silver-paste electrodes followed by soft soldering below 250 °C to avoid depoling, or by conductive adhesive.
What surface finishes work on KNN PURE?
Screen-print and fire silver electrodes at roughly 700–800 °C, or sputter Cr/Au. Pole at 2–4 kV/mm in silicone oil at 80–120 °C and age 24 h; finished parts need moisture-barrier packaging.
Can KNN PURE be formed, bent or molded?
Dry pressing, cold isostatic pressing and tape casting are all usable. The sintering window is narrow (about ±20 °C), so fire in sealed saggars with excess alkali in the batch to compensate K/Na volatilisation, otherwise second phases and abnormal grain growth appear.
What is the maximum service temperature of KNN PURE?
KNN PURE is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- ASM Engineered Materials Handbook Vol.4: Ceramics and Glasses — ASM International (1991)
- IEEE 176 Standard on Piezoelectricity — IEEE (1987)
- Lead-free piezoceramics (KNN) property reviews — Journal of the American Ceramic Society / Journal of Materials Chemistry C (2019)
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.