S. N. Popov

Piezoelectric properties of crystals of some protein aminoacids and their related compounds

Growth of single crystals of some protein aminoacids and synthesis and growth of single crystals of their related compounds are reported. The temperature dependence of the integrated piezoelectric response of the single crystals grown was studied in the temperature range 120–320 K. The specific features in the temperature dependence are shown to be due to the enhanced damping of elastic vibrations in the crystals, which originates from the elastic vibrations being coupled to thermally activated rotation of the CH3 and NH3 molecular groups.

Piezoelectricity in protein amino acids

The piezoelectric activity of protein amino acids and their compounds has been measured using the pulse method at a frequency of 10 MHz. It has been established that, at room temperature, the piezoelectric effect is not observed in α-glycine (achiral amino acid) and protein amino acids of the L modification, namely, methionine, phenylalanine, and tryptophan. An assumption has been made that this phenomenon is associated with the enhanced damping of elastic vibrations excited in samples due to the piezoelectric effect.

Pyroelectric, piezoelectric, and polarization responses of glycine phosphite crystals with an admixture of glycine phosphate

Temperature dependences of the pyroelectric, piezoelectric, and polarization responses of glycine phosphite crystals containing different amounts of glycine phosphate were studied in the range 120–320 K. The experimental data obtained suggest the presence of a built-in bias field oriented along the twofold symmetry axis in these crystals. This field was found to be 5 kV/cm. It is suggested that the built-in bias plays a decisive role in the formation of the pyroelectric and piezoelectric crystal responses in the temperature interval 225–280 K, which is significantly higher than the ferroelectric phase transition point in nominally pure glycine phosphite crystals (224 K).

Phonon echo in L-alanine

Phonon echo signals have been observed in a finely-dispersed crystalline powder of the L-alanine amino acid. Measurements of the relaxation time T2 have revealed a phase transition in L-alanine crystals at a temperature of about 170 K.

Phase transitions in crystals of protein amino acids

The temperature dependence of the piezoelectric response of many protein amino acids and their compounds exhibits a sharp increase in the piezoelectric response signals at a certain temperature. It has been shown using the example of the known ferroelectrics without a piezoelectric effect in the paraphase (triglycine sulfate, glycine phosphite, trisarcosine calcium chloride) that such an increase in the piezoelectric response is associated with the structural phase transition to the low-symmetry piezoelectric phase with a large number of piezoelectric coefficients. The specific features of the phase transitions with the symmetry change D2-C2 have been discussed.

Unusual electromechanical effects in glycine

Unusual piezoresponse signals have been observed in glycine aminoacid powder at a frequency near 10 MHz, which exhibited a regular pattern in time determined by a periodic phase variation in the elastic vibrations of individual powder particles. This phenomenon results from the formation of spatial structures in glycine powder under the action of a strong rf field.

Diserine Sulfate Monohydrate: Symmetry, Piezoelectric Properties, and Phase Transitions

A new compound, diserine sulfate monohydrate, was synthesized, and single crystals of this compound were grown. X-ray diffraction studies were carried out, and the temperature dependences of the piezoelectric response of these crystals were measured. A conclusion was drawn that the crystals are orthorhombic with the space symmetry group C1v-Pmm2 and that they apparently undergo phase transitions at 340 and 255 K.

Phase transition in sarcosine phosphite single crystals

Single crystals of sarcosine phosphite (SarcH3PO3) have been grown. The amino acid sarcosine is an isomer of the protein amino acid alanine. Both amino acids are described by the same chemical formula but have different structures; or, more specifically, in contrast to the alanine molecule, the sarcosine molecule has a symmetric structure. It has been found that the sarcosine phosphite compound undergoes a structural phase transition at a temperature of approximately 200 K. This result has demonstrated that compounds of achiral amino acids are more susceptible to structural phase transitions.

Effect of electric field on the smeared phase transition in crystals PbIn1/2Nb1/2O3-28PbTiO3 and PbIn1/2Nb1/2O3-37PbTiO3

The effect of a direct-current electric field (0 < E < 3 kV/cm) on the smearing of the phase transition and the Curie-Weiss exponent (γ) for two PbIn1/2Nb1/2O3-28PbTiO3 and PbIn1/2Nb1/2O3-37PbTiO3 crystals lying at different distances from the morphotropic phase boundary has been investigated. The universal Curie-Weiss law has been used to approximate the temperature dependences of the dielectric permittivity. It has been shown that the more remote is the crystal from the morphotropic phase boundary, the larger is the exponent γ and, consequently, the more smeared is the phase transition (in the zero field, γ = 1.67 and 1.49 for PbIn1/2Nb1/2O3-28PbTiO3 and PbIn1/2Nb1/2O3-37PbTiO3, respectively). It has been found that a weak electric field (no greater than 2–3 kV/cm) in the case of the more smeared phase transition almost does not affect the Curie-Weiss exponent, whereas for the PbIn1/2Nb1/2O3-37PbTiO3 crystal, this exponent decreases with increasing electric field strength and approaches γ = 1, which is characteristic of the conventional ferroelectric.

Piezoelectric effect in diserine sulfate monohydrate crystals

The anisotropy of the piezoelectric response in diserine sulfate single crystals has been studied at room temperature. The electromechanical coupling coefficient and the piezoelectric coefficients have been evaluated.