S. D. Milovidova

Properties of nanoporous aluminum oxide with triglycine sulfate and Rochelle salt inclusions

The possibility of producing the ferroelectric state in nanoporous aluminum oxide loaded with triglycine sulfate and Rochelle salt has been studied. Our dielectric, pyroelectric and emission measurements give grounds to suggest that this state persists in the composites under study up to temperatures exceeding the Curie point of bulk crystals by several tens of degrees.

Dielectric Properties of Ferroelectric Composites with TGS Inclusions

Dielectric properties of composites consisting of nanoporous aluminium oxide Al2O3 or glass SiO2 with inclusions of the ferroelectric triglycine sulphate (TGS) are investigated in the present work. Our investigations enable us to assume the presence of ferroelectric state in these materials.

Dielectric Properties of Composites Based on Nanocrystalline Cellulose and Triglycine Sulfate

This paper is devoted to studies of properties of composites based on nanocrystalline cellulose and triglycine sulfate. The presence of one or two peaks in the temperature dependence of dielectric permittivity was revealed and their shift to higher temperatures as compared with the bulk TGS to 54°C and 100°C was detected, respectively. An explanation of the results is related to the appearance of internal bias fields in the nanocomposites.

APPEARANCE OF INTERNAL BIAS FIELD IN FERROELECTRIC GROWTH PROCESS

Abstract The growth regularities of the internal bias field Eb formation have been investigated in pure triglycine sulphate crystals, as well as in crystals doped with chromium or α-alanine. All crystals were grown in the ferrophase from the seed of the pivot form oriented by its axis along the non-polar crystal axis Z. It was found that the bias field had different signs in the samples lying on opposite sides of the seed along the polar axis Y in the crystals with chromium impurity and pure crystals and the same sign in α-alanine doped ones. The probable mechanism of Eb field formation is suggested for both cases.

Dielectric properties of composites based on nanocrystalline cellulose with triglycine sulfate

The dielectric properties and frequency dispersion of the dielectric characteristics of nanocrystalline cellulose-triglycine sulfate composites have been studied in the low- and infralow-frequency ranges (from 10−3 to 103 Hz) in a weak electric field. It has been shown that the phase transition in these composites is diffuse and displaced to the higher temperatures range as compared to the transition in bulk triglycine sulfate. In the composites under study, a significant dispersion of the permittivity, presumably caused by a positive Maxwell-Wagner relaxation, is observed.

Structure and Electrical Properties of Nanocomposites with TGS Inclusions

The structure and properties of nanocomposite structures based on porous matrix with a triglycine sulfate inclusions have been investigated. Interrelation between the behavior of the dielectric parameters (dielectric susceptibility, the Curie temperature) and structural features of the composite has been established. It is shown that changing the size of ferroelectric inclusions and their relative positions may have a significant effect on the phase transition temperature.

Electrophysic Properties of TGS Crystals Grown at the Temperatures Below 0°C

The work is concerned with the investigations of the properties of triglycine sulphate (TGS) crystal grown at the temperatures below 0°C (from −3°C to −5°C). An interest to the growth of the crystals at these temperatures is due to the fact the temperature of eutectics in “triglycine sulphate—water” system is in the range of 0°C ÷ −7°C. All of the grown crystals are characterized by the growth planes specific for TGS with the greatest growth rate along the polar axis. The shift of temperature of the phase transition towards the higher temperatures by 0.5 ÷ 0.7 degree was found in this system. It means hardness of domain structure of the grown crystals that is confirmed by the high and stable values of pyroelectric coefficient. The obtained results are associated with the changes of hydrogen bonds and structure of water occurring near 0°C.

Thermally Stimulated Electron Emission in the Paraelectric Phase of Triglycine Sulfate Crystals Heated at a High Rate

Thermally stimulated electron emission is experimentally observed in ferroelectric triglycine sulfate (TGS) crystals in a temperature range whose upper limit is 10–15 K above the Curie point. Samples of a nominally pure and a chromium-doped TGS crystal, heated at different constant rates q=dT/dt, are investigated. It is shown that an increase in the heating rate results in increased emission current density over the entire temperature range investigated. The temperature at which emission arises depends only slightly on the rate q. At the same time, the temperature at which emission ceases increases monotonically with increasing q; if q is less than 1 K/min, this temperature is below the Curie point, while at q=4–5 K/min, this temperature becomes as large as 60–65°C, which is more than 15°C above the Curie point. In chromium-doped TGS crystal, the electron emission onset temperature is close to that of pure TGS, but the width of the temperature range over which emission is observed in the paraelectric phase is approximately two times less than in the case of pure TGS heated at the same rate. The emission disappearance below the Curie point (in the ferroelectric phase) at low q is explained as a result of full emptying of the electron traps under slow heating. The reason for the occurrence of emission above the Curie point is related to the charges that shield the spontaneous polarization and, because of their slow relaxation, persists in the paraelectric phase.

Electron emission in ferroelectrics with different value of coercive field

Abstract The relation between main parameters of processes of switching and emission of electrons out of ferroelectrics — coercive field of emission is investigated. It is shown that temperature, concentrational and frequency dependencies of threshold field can be explained by the corresponding dependencies of coercive field.

Investigation of dielectric relaxation in ferroelectric composite nanocrystalline cellulose – triglycine sulfate

ABSTRACT Dielectric relaxation in ferroelectric composite nanocrystalline cellulose – triglycine sulfate in the frequency range from 103 to 106 Hz in a weak measuring field (1 V·cm−1) from room temperature to the phase transition temperature of these composites (+54°C) has been investigated. Two series of nanocomposites were used: the first one with the perpendicular directions of nanochannels with respect to the sample surface and the second one – with parallel. The typical for single-crystal triglycine sulfate maximum of the imaginary part of dielectric permittivity at frequencies (105 Hz – 106 Hz) in the case of composites nanocrystalline cellulose – triglycine sulfate is shifted to the range of lower frequencies (104 Hz – 105 Hz).