• Naturally Occuring Substances
• Naturally Occuring Biotic Substances
• Artificial Substances : Crystals
• Artificial Substances : Ceramics
• Lead Free Piezo Ceramics

Lead-free piezoceramics

More recently, there is growing concern regarding the toxicity in lead-containing devices driven by the result of restriction of hazardous substances directive regulations. To address this concern, there has been a resurgence in the compositional development of lead-free piezoelectric materials.

Sodium potassium niobate (NaKNb). In 2004, a group of Japanese researchers led by Yasuyoshi Saito discovered a sodium potassium niobate composition with properties close to those of PZT.

Bismuth ferrite (BiFeO₃) is also a promising candidate for the replacement of lead-based ceramics.

Sodium niobate NaNbO₃

So far, neither the environmental impact nor the stability of supplying these substances have been confirmed.

Polymers

Polyvinylidene fluoride (PVDF):

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  Polyvinylidene Fluoride

(Polyvinylidene Fluoride, or PVDF is a highly non-reactive and pure thermoplastic fluoropolymer.PVDF is a specialty plastic material in the fluoropolymer family; it is used generally in applications requiring the highest purity, strength, and resistance to solvents, acids, bases and heat and low smoke generation during a fire event. Compared to other fluoropolymers, it has an easier melt process because of its relatively low melting point of around 177 °C.)

PVDF exhibits piezoelectricity several times greater than quartz. Unlike ceramics, where the crystal structure of the material creates the piezoelectric effect, in polymers the intertwined long-chain molecules attract and repel each other when an electric field is applied.