Spontaneous polarisation in the mixed ferroelectric DBP x DBPI1-x crystals

Thermal behaviour of spontaneous polarisation, obtained from pyroelectric measurements of ferroelectric hydrogen bonded deuterated (betaine Phosphate) x (betaine phosphite) 1-x is investigated forx = 0.01 0.03 and 0.05. In the region of the ferroelectric phase transition the spontaneous polarisation is explained by quasi-one-dimensional Ising model. Spontaneous polarisation saturates at 1.8 and 0.16 μC/cm 2 for DBP 0.01 DBPI 0.99 and DBP 0.03 DBPI 0.97, respectively.