Phase transitions of K2CrO4 crystals

The electrical conductivity measurements on single crystals of K2CrO4 have been carried out in the temperature range from 580 to 1070 K. The bulk ioni c conductivity along the three principal crystallographic axes has been det ermined by means of complex impedance formalism. The ionic conductivity in the low-temperature phase beta follows closely the classical Arrhenius law up to around 890 K (similar to T-c - 50 K). From 890 K, the slope of the co nductivity curve increases up to T-c and it is attributed to the existence of a pretransitional region which may be a consequence of the significant r otational disorder of chromate ions below its phase transition. Unusual beh aviour in the temperature dependence of the vibrational mode (vl) of chroma te ions has been observed in roughly the same temperature range. The dielec tric properties are similar to the prototype K2SO4 crystal and are discusse d concerning an intermediate phase above T-c.