RADIATION AND ELECTRIC-FIELD-INDUCED EFFECTS ON THE ORDER-DISORDER PHASE IN LITHIUM SODIUM-SULFATE CRYSTALS

The temperature dependence of specific heat at constant pressure, Cp(T ), has been measured for lithium sodium sulphate, LiNaSo(4) crystals, at different gamma-radiation doses and external bias electric field (E (b)), in the temperature range 300-900 K. A nonlinear dependence of tr ansition temperature, T-l and a remarkable change in the thermodynamic parameters, were obtained as the effect of both electric field and ga mma-radiation. The effect of gamma-radiation doses on the phase transi tion in LiNaSO4 crystals was explained as due to an internal bias fiel d, E(b), originating from the interaction of polar defects with the or der parameter of the host lattice. The internal bias field effect on t he behaviour of Cp(T) in LiNaSO4 crystals was similar to that of the e xternal electric field (E).