KNN
KNN is potassium sodium niobate, a lead-free perovskite piezoceramic developed as a RoHS-driven substitute for PZT, offered pure, low-temperature-sintering (LTS), hard-doped, hot-pressed (HP) and textured (TGG).
Reference datasheet — KNN is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the LTS condition
KNN tempers and conditions
KNN is supplied in 5 conditions, soft to hard. LTS is the default FabDigit quotes; the values on this page are for it.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
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?
KNN is potassium sodium niobate, a lead-free perovskite piezoceramic developed as a RoHS-driven substitute for PZT, offered pure, low-temperature-sintering (LTS), hard-doped, hot-pressed (HP) and textured (TGG). It is used where lead-free actuators and sensors are mandated, as pressed discs and rings or tape-cast sheets with fired silver electrodes. Density 4.5 g/cm³, modulus 105 GPa, thermal conductivity 2.5 W/m·K, service to 150 °C. Piezoelectric output is moderate, the sintering window is narrow and parts are moisture-sensitive; PZT remains the choice when performance outweighs lead-free compliance. KNN has a density of 4.5 g/cm³ (0.163 lb/in³), lighter than 55% of ceramic grades. It melts at 1,140°C (2,084 °F). The elastic modulus is 105 GPa (15.2 Msi).
What is KNN used for?
- lead-free piezo actuators
- lead-free sensors
- green electronics components
Limitations
- Limited service temperature — 150°C (302 °F), worse than 90% of ceramic grades
- Low fracture toughness — 1 MPa·√m (0.91 ksi·√in), worse than 84% of ceramic grades
- Poor heat conductor — 2.5 W/m·K (1.44 BTU/hr·ft·°F), worse than 83% of ceramic grades
KNN properties
Typical room-temperature values for KNN-LTS; bars are the position among ceramic grades.
Physical4
KNN has a density of 4.5 g/cm³ (0.163 lb/in³), lighter than 55% of ceramic grades. It melts at 1,140°C (2,084 °F).
Mechanical9
The elastic modulus is 105 GPa (15.2 Msi).
Thermal5
KNN is rated for continuous service to 150°C (302 °F). It conducts heat at 2.5 W/m·K (1.44 BTU/hr·ft·°F), worse than 83% of ceramic grades. Thermal expansion is 7 µm/m·K (3.89 µin/in·°F).
Electrical5
KNN is an electrical insulator with a dielectric strength of 6 kV/mm (152.4 V/mil) and a resistivity of 1×10⁹ Ω·m.
Chemical & Environmental2
Corrosion resistance is good (62/100), worse than 70% of ceramic grades.
Sustainability4
Producing a kilogram of KNN 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's machinability is not recommended (8/100, better than 69% of ceramic grades).
Common Calculations2
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the ceramic family
Yield strength against density for every ceramic grade FabDigit runs. KNN is highlighted; hover a dot for its name, or open the interactive family chart.
Working with KNN
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.
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 |
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.
How much does KNN cost?
KNN is a high-cost ceramic ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
KNN — frequently asked
What is KNN used for?
KNN is typically used for lead-free piezo actuators, lead-free sensors and green electronics components. In short: lead-free PZT alternative; narrow sintering window; lower density than PZT.
Is KNN easy to machine?
Not especially — machinability is rated not recommended (8/100, better than 69% of ceramic grades). After firing, only diamond grinding, ultrasonic drilling or laser cutting is possible; machining in the green or bisque state is by far the cheapest route. Anneal after grinding to remove surface residual stress before poling.
Can KNN be welded?
The ceramic is not weldable. Metal connection is made through fired silver-paste electrodes followed by soft soldering below 250 °C to avoid depoling, or by conductive adhesive.
What surface finishes work on KNN?
Screen-print and fire silver electrodes at roughly 700–800 °C, or sputter Cr/Au. Pole at 2–4 kV/mm in silicone oil at 80–120 °C and age 24 h; finished parts need moisture-barrier packaging.
Can KNN be formed, bent or molded?
Dry pressing, cold isostatic pressing and tape casting are all usable. The sintering window is narrow (about ±20 °C), so fire in sealed saggars with excess alkali in the batch to compensate K/Na volatilisation, otherwise second phases and abnormal grain growth appear.
What is the maximum service temperature of KNN?
KNN is rated for continuous use to about 150°C (302 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does KNN cost?
KNN is a high-cost ceramic ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
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; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.