Dielectric properties of self-assembled spherulite films of organic ferroelectric 2-methylbenzimidazole

Highly Oriented Organic Ferroelectric Films with Single-Crystal-Level Properties from Restrained Crystallization

“…In most ferroelectrics, P r decreases with temperature because it is expected to vanish at the ferroelectric-to-paraelectric phase transition temperature. However, for proton-transfer-type ferroelectricity that relies on long-range order of hydrogen bonds, like MBI and CA, because the elongation of hydrogen bonds dominates the thermal expansion, a near-linear relationship between strain and ferroelectricity is expected, which has also been observed previously in MBI and CA …”

Structural Properties and Dielectric Hysteresis of Molecular Organic Ferroelectric Grown from Different Solvents

“…For the growth of MBI films in a closed volume, an organic solvent N, N-dimethylformamide [6] was used. The texted MBI films with spherulite structure were grown by evaporation from the ethanol solution [7][8][9][10]. Similar types of texted MBI films have been obtained by physical vapor deposition (PVD) method [11].…”

“…For this reason, MBI crystal structure is described by pseudosymmetric tetragonal space group P4 2 /n [33]. Assignment of the MBI crystal to a noncentrosymmetric Pn space group is proved mainly by the presence in MBI crystals of ferroelectric [5][6][7][8][9][10][11] and piezoelectric [5,34] properties, and the observation of ferroelectric [5,12] and ferroelastic domains [12].…”

“…The crystals of MBI attract attention, because at room temperature they have low values of coercive fields E c ~2-3 V/µm, which is about an order of magnitude lower than in ferroelectric polymers, and spontaneous polarization P s ~5-7 µC/cm 2 . In micron-thick MBI films obtained by the method of scraping (solution shearing) [6] and in textured MBI films obtained by evaporation from solution [7][8][9][10] or physical vapor deposition [11], polarization switching occurred in an electric field of several Volts. Ferroelectric properties of MBI crystals and films are retained up to the melting point T m ≈ 450 K, and an important property of MBI is the ability to switch polarization in different directions perpendicular to the pseudotetragonal axis by low fields [5][6][7][8][9][10][11].…”

“…MBI single crystals and films have been grown by vacuum sublimation [5,11] or evaporation from a solution of chemically prepared MBI powder in organic solvents [6][7][8][9][10]. It is known that, when growing crystals from solutions, the solvent can significantly affect the properties of the crystals obtained, and at present the influence of the solvent is being intensively studied [15][16][17][18][19][20][21][22][23][24][25][26].…”