The Surface Structure of Ferroelectric Crystal like a Ammonium Sulfate Type crystals.

Potassium tellurite K_2TeO_3was found a new ferroeclectics by the measurements of dielectric constants.It was found that a new ferroelectric potassium tellurite undergoes successive phase transitions.The domain structure of the single crystal of ferroelectric potassium tellurite under the polarizing microscope，was observed at room temperature。The irregular stripe pattern was observed in(Ab)-plane.The a-face is covered with the scale-like patterns.Potassium tellurite shows successive phase transitions.This was a similar behavior with ammomium fluoroberyllate，(NH_4)_2BeF_4，and potassium selenate，K_2SeO_4.The transiton temperature of potassium tellurite is relatively higher than those crystals.Then we investigated to clearfy the difference in ferroelectricity between these substances by the microscopic observation under wide temperature range.The domain movement on the surface in ammonium sulfate，(NH_4)_2SO_4，single crystal is detected with the movement of the baundary of the retardation。There is no change for the retardation in immcomensurate phase in(NH_4)_2BeF_4and K_2SeO_4crystals.The single crystal which were grown by the slow evaporation from an aqueous solutioon of K_2TeO_3was found a K_2Te_2O_5·3H_2O by X-ray single crystal diffraction。The modification on the surface in potassium tellurite was caused by the efflorescence.

Potassium tellurite K_2TeO_3 was found a new ferroeclectics by the measurements of dielectric constants. It was found that a new ferroelectric potassium tellurite undergoes successive phase transitions. The domain structure of the single crystal of ferroelectric potassium tellurite under the polarizing microscope, was observed at room temperature. The irregular stripe pattern was observed in (ab)-plane. The a-face is covered with the scale-like patterns. Potassium tellurite shows successive phase transitions. This was a similar behavior with ammomium fluoroberyllate, (NH_4)_2BeF_4, and potassium selenate, K_2SeO_4. The transiton temperature of potassium tellurite is relatively higher than those crystals. Then we investigated to clearfy the difference in ferroelectricity between these substances by the microscopic observation under wide temperature range.The domain movement on the surface in ammonium sulfate,(NH_4)_2SO_4, single crystal is detected with the movement of the baundary of the retardation. There is no change for the retardation in immcomensurate phase in (NH_4)_2BeF_4 and K_2SeO_4 crystals. The single crystal which were grown by the slow evaporation from an aqueous solutioon of K_2TeO_3 was found a K_2Te_2O_5・ 3H_2O by X-ray single crystal diffraction. The modification on the surface in potassium tellurite was caused by the efflorescence.