The desired piezoelectric material properties depend on the application. High-power applications typically require large d ij s but are tolerant to frequency and temperature instability . Typical piezoelectric coefficients for Pb(Zr,Ti)O 3 (PZT) can exceed d 33 = 600 pC/N . Low power applications, such as RF filters, on the other hand, require stable coefficients as a function of frequency. AlN, a material used for this purpose, has * elin.dypvik.sodahl@nmbu.no a small but stable d 33 of 3.4 pC/N . State-of-the-art polymer piezoelectric materials, attractive for flexible devices such as energy harvesting cantilevers, are based on the polymer polyvinylidene fluoride (PVDF). The piezoelectric coefficient of PVDF-co-trifluoroethylene(TrFE) is d 33 = -65.3 pC/N . Although piezoelectrics like PZT, AlN, and PVDF have important commercial applications, there remain a large parameter spaces between these known materials where combinations of properties, such as soft or flexible materials with robust or stable piezoelectric responses, are yet to be found. Plastic ionic molecular crystals, which consist of inorganic anions bonded to organic cations, are an emerging class of ferroelectric and piezoelectrics that could fill many gaps in the material property space . These materials possess immense compositional tunability, low processing temperatures compared to inorganic materials, and compositions with toxic and scarce elements such as Pb, Ba, and Co can be avoided. They exhibit a broad range of bonding properties -including van der Waals forces, hydrogen bonding, charge-transfer, and intermolecular orbital hybridization -which gives rise to unique mechanical and functional properties. The key example of a unique property is the existence of a "plastic" high-temperature mesophase, where molecules retain lattice order but increase their degree of local orientational disorder, introducing molecular rotation into the structure. In the mesophase the material has weakened intramolecular bonding and ease of dislocation movement, causing it to become malleable and deformable into desired shapes . However, the molecular rotations do not only play a role in the plasticity and phase transitions of plastic crystals, they are also involved in the polarization switching of ferroelectric materials .