Coexistence of polar and non-polar phases in ND₄DSeO₄ crystals

Abstract

The temperature variation of the dielectric constant has been measured in ND₄DSeO₄ with over 90 mole percent of deuterium content. The grown crystals having P2₁2₁2₁ symmetry at room temperature, after being heated above 367 K, exhibit irreversible phase transition to I2 symmetry. At room temperature the phase I2 is not stable unlike for the crystal with lower degree of deuteration and the crystal returns to P2₁2₁2₁ phase during about 60 hours. A t 275 K occurs the phase transition to I1 but only from I2 phase.