PHASE-TRANSITIONS OF TL2ZNBR4 AND TL2COBR4

The dielectric and phase transitional properties were investigated for Tl2ZnBr4 and Tl2CoBr4, both of which are compounds having the crystal structure of Sr2GeS4-type at room temperature. The differential therm al analysis(DTA) and dielectric measurements revealed that both crysta ls have the transition at around 18 K accompanied by a lambda-type die lectric constant anomaly and the so-called alpha-beta transition at ar ound 480 K from the Sr2GeS4-type phase to the high temperature beta-K2 SO4-type phase.