Functional Ceramics
Functional ceramics are specified for what they do electrically, not what they carry: piezoelectric lead zirconate titanate (PZT) turns voltage into motion and motion into charge with a d₃₃ of 300–600 pC/N; manganese-zinc and nickel-zinc ferrites store magnetic flux in transformer and inductor cores; barium- and strontium-titanate dielectrics give multilayer capacitors permittivities of 1,000–15,000; zinc-oxide varistors clamp surges and doped titanates make self-limiting PTC heaters and NTC thermistors. Strength is modest (50–100 MPa) and the numbers that matter are Curie temperature, coupling factor, permeability and loss.
Popular functional ceramic grades
Compare in the explorer| Grade | Yield, MPa | Tensile, MPa | Density, g/cm³ | Machinability | Weldability | Best for |
|---|---|---|---|---|---|---|
| PZT | 80 | 75 | 7.75 | Not recommended | Not recommended | General piezoceramic for transducers and sensors |
| PZT-4 | — | 75 | 7.5 | Not recommended | — | Hard grade for high-power ultrasonic transmitters |
| PZT-5H | — | 75 | 7.5 | Not recommended | — | Soft grade: actuators, receivers, largest signal |
| PZT-8 | — | 30 | 7.6 | Not recommended | — | Lowest loss under the highest drive levels |
| MnZn Ferrite | — | 30 | 4.85 | Poor | — | Power transformer and inductor cores to 1 MHz |
| BaTiO3 | — | 45 | 5.9 | Not recommended | — | Lead-free piezo and Class II capacitor dielectric |
| ZnO Varistor | — | — | 5.55 | Not recommended | — | Surge clamping in arresters and protection |
Choose functional ceramics for
Ultrasonic transducers, sonar and flow sensors; piezo actuators, fuel injectors and precision positioners; transformer, inductor and EMI-suppression cores; multilayer and RF capacitor dielectrics; surge arresters and varistors; self-regulating PTC heaters and NTC temperature sensors; and single-crystal LiNbO3 or LiTaO3 substrates for surface-acoustic-wave filters and electro-optics.
Look elsewhere when
The part is structural or a wear surface (Alumina 96 or Zirconia Y-TZP — functional ceramics are weak and chip easily), the operating temperature is more than about half the Curie point (PZT-5H depoles above roughly 100 °C; move to PZT-4, PZT-8 or PbNb2O6), the assembly must be lead-free (BaTiO3, KNN or BNT instead of PZT), or the requirement is only electrical insulation, for which Alumina 99.5 or Steatite are cheaper and stronger.
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Functional ceramic by application
- Ultrasonic power and sonar
- PZT-4 rings and discs for cleaning tanks, welders and sonar projectors; PZT-8 when the duty cycle and drive field are highest and heating must stay low.
- Actuators and sensors
- PZT-5H stacks, plates and benders for positioners, injectors, accelerometers and hydrophones; PLZT where a transparent electro-optic ceramic is needed; PbNb2O6 for NDT probes that must be broadband or run hot.
Working with functional ceramic
- Forming & sintering
- Piezoceramics and dielectrics are pressed or tape-cast and sintered at 1,200–1,300 °C — PZT in a lead-oxide-controlled atmosphere to hold stoichiometry — with about 15 % shrinkage. Ferrites are pressed and sintered at 1,300–1,400 °C in controlled oxygen. Electrodes are fired-on silver or sputtered nickel or gold, and PZT is then poled at 2–4 kV/mm in hot oil at 100–150 °C.
- Grinding & lapping
- Thickness sets the resonant frequency, so PZT plates and discs are lapped to ±5 µm and parallel within a few microns before electroding; diameters are ground to ±0.05 mm. Ferrite cores are ground on mating faces so the air gap — which sets inductance — is held to ±10 µm. Neither material tolerates heat in grinding: poled PZT depoles, ferrite cracks.
- Joining & sealing
- PZT elements are bonded with conductive epoxy or soldered at the lowest practical temperature (well below the Curie point; below about 150 °C for PZT-5H) with a low-melting alloy; stack actuators are epoxy-laminated under pressure. Ferrite halves are clamped or glued with a spacer to set the gap; potted assemblies need a compliant compound so stress does not shift permeability or piezo response.
- Tolerances & design rules
- Keep operating temperature below half the Curie point (PZT-4 about 325 °C, PZT-5H about 195 °C, BaTiO3 120 °C), avoid tensile stress across the poling direction, and specify electrode pattern and poling direction on the drawing. Frequency tolerance of ±2–5 % is standard; tighter means individual lapping and testing.
Other ceramic series
Functional Ceramics — frequently asked
What is functional ceramic?
Functional ceramics are specified for what they do electrically, not what they carry: piezoelectric lead zirconate titanate (PZT) turns voltage into motion and motion into charge with a d₃₃ of 300–600 pC/N; manganese-zinc and nickel-zinc ferrites store magnetic flux in transformer and inductor cores; barium- and strontium-titanate dielectrics give multilayer capacitors permittivities of 1,000–15,000; zinc-oxide varistors clamp surges and doped titanates make self-limiting PTC heaters and NTC thermistors. Strength is modest (50–100 MPa) and the numbers that matter are Curie temperature, coupling factor, permeability and loss.
Which grade of functional ceramic should I use?
PZT-4 for high-power transmitters — ultrasonic cleaners, welders and sonar — where low loss under drive matters, and PZT-8 for the same at the highest drive levels. PZT-5H (or a generic PZT soft grade) for receivers, actuators and sensors that need the largest displacement or signal, accepting a Curie point near 195 °C and more loss. PZT-2 is a niche hard grade; PbNb2O6 (lead metaniobate) keeps working to 500 °C with low mechanical Q for broadband NDT probes, and BaTiO3, BNT and KNN are the lead-free options where regulation demands it. For magnetics, MnZn Ferrite grades such as N87, PC40, PC44 and 3C90 are the power-transformer cores to about 1 MHz, and the NiZn grades Material 43 and Material 61 handle EMI suppression and RF above that. For capacitors, C0G/NP0 is the stable Class I dielectric, X7R the general-purpose Class II to 125 °C, X8R to 150 °C, and Y5V or Z5U only where capacitance per volume beats stability.
Which grade of functional ceramic is easiest to machine?
MnZn Ferrite (machinability poor, 15/100), then Material 61 (12/100).
PZT-4, PZT-5H or PZT-8 — hard or soft?
Hard grades (PZT-4, PZT-8; Navy Types I and III) have low dielectric and mechanical loss, so they run cool under high drive and are chosen for transmitters, ultrasonic cleaning and welding; their d₃₃ is about 290 and 225 pC/N with Curie points around 325 and 300 °C. Soft grades (PZT-5H, Navy Type VI) give about twice the displacement and charge output (d₃₃ near 590 pC/N) at the price of higher loss and a Curie point of about 195 °C — right for receivers, sensors and low-duty actuators. Hard for power out, soft for signal or motion.
Which ferrite for a switch-mode transformer?
A manganese-zinc power ferrite: N87, PC40, PC44 or 3C90 are near-equivalents with initial permeability around 2,000–2,300, saturation near 0.4–0.5 T, Curie temperature above 200 °C and lowest core loss between about 25 and 500 kHz at 80–100 °C. Above 1–2 MHz, or for common-mode chokes and EMI beads, the higher resistivity of NiZn grades such as Material 43 (broadband suppression) and Material 61 (RF inductors to 25 MHz) wins. Gap the core for DC bias; the ground gap face sets the inductance tolerance.