Ferroelectric properties of doped triglycine sulfate crystals grown at negative temperatures

The effect of Cr³⁺ impurity ions on the dielectric and pyroelectric properties of triglycine sulfate crystals grown at temperatures below 0°C is studied. The Curie temperature T _C of the chromium-containing crystals is 0.2–0.4°C lower than that of the impurity-free crystals grown at conventional temperatures. A stable reproducibility of the results of the pyroelectric measurements for the crystals studied is established, which indicates that the polar state in crystals is stabilized by growth defects.     

Thermostimulated electron emission from polar cleavage of a triglycine sulfate crystal

This paper reports the results of experimental investigations into thermostimulated electron emission from the positive and negative cleavage surfaces of a ferroelectric triglycine sulfate crystal. It is shown that the current density j of emission from the negative surface is universally higher than that from the positive surface over the entire range from room temperature to the Curie point. The shape of the j(T) curves substantially depends on the degree of natural unipolarity of the studied samples. The results obtained are discussed in the framework of the mechanism of field electron emission from the surface electronic states.     

Thermally stimulated electron emission from chromium-doped triglycine sulfate in the paraelectric phase

Thermally stimulated electron emission from a ferroelectric chromium-doped triglycine sulfate (TGS) crystal was experimentally observed to occur in a temperature range 6 K above the Curie point from samples heated at a relatively high rate. Increasing the heating rate q was shown to cause the emission current density to increase throughout the temperature range studied. The emission onset temperature in chromium-doped TGS depends only weakly on the rate q and is close to that for pure TGS, and the emission cutoff temperature grows monotonically with q at comparatively low heating rates and stabilizes at high q. At the same time, the interval of emission extension into the paraelectric phase here is about one half that for pure TGS heated at the same rate. The specific features of emission observed for this crystal can be assigned to relaxation of the charges screening the spontaneous polarization. The lower emission cutoff temperature for the chromium-doped TGS compared to that for pure TGS is accounted for by the shorter Maxwellian relaxation time in the doped crystal.