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Ferroelectric polymers, such as polyvinylidene fluoride (PVDF), ... In order for this effect to happen, the material must be below its Curie Temperature. [5]
PVDF is a specialty plastic used in applications requiring the highest purity, as well as resistance to solvents, acids and hydrocarbons. PVDF has low density 1.78 g/cm 3 in comparison to other fluoropolymers, like polytetrafluoroethylene. It is available in the form of piping products, sheet, tubing, films, plate and an insulator for premium wire.
The Curie–Weiss law is a simple model derived from a mean-field approximation, this means it works well for the materials temperature, T, much greater than their corresponding Curie temperature, T C, i.e. T ≫ T C; it however fails to describe the magnetic susceptibility, χ, in the immediate vicinity of the Curie point because of ...
Other ferroelectric materials used include triglycine sulfate, polyvinylidene fluoride (PVDF) and lithium tantalate. [27] A single atom thick ferroelectric monolayer can be created using pure bismuth. [28] It should be possible to produce materials which combine both ferroelectric and metallic properties simultaneously, at room temperature. [29]
Polyvinylidene fluoride (PVDF) has a very high permittivity of 18 to 20, which allows large amounts of energy to be stored in a small space (volumetric efficiency). However, it has a Curie temperature of only 60 °C, which limits its usability. Film capacitors with PVDF are described for one very special application, in portable defibrillators.
At 95.6 °C the two forms can co-exist. Another example is tin, which transitions from a cubic crystal below 13.2 °C to a tetragonal crystal above that temperature. In the case of ferroelectric or ferromagnetic crystals, a transition temperature may be known as the Curie temperature.
Organic polymer PMs, such as PVDF, have low Young's modulus compared to inorganic PMs. Piezoelectric polymers (PVDF, 240 mV-m/N) possess higher piezoelectric stress constants (g 33), an important parameter in sensors, than ceramics (PZT, 11 mV-m/N), which show that they can be better sensors than ceramics. Moreover, piezoelectric polymeric ...
is a material-specific Curie constant (K). Pierre Curie discovered this relation, now known as Curie's law, by fitting data from experiment. It only holds for high temperatures and weak magnetic fields.