Effect of Uniaxial Pressure on the Ferroelectric Phase Transition in Pb$\text{}_{5}$Ge$\text{}_{3}$O$\text{}_{11}$:Ba Crystals

The effect of uniaxial pressure up to 1 kbar applied perpendicular and parallel to c-axis, on the Curie temperature and electric permittivityε$\text{}_{c}$ of Ba-doped Pb$\text{}_{5}$Ge$\text{}_{3}$O$\text{}_{11}$ single crystals was investigated. The Curie temperature decreases with uniaxial pressure and the coefficientγ$\text{}_{i}$ (γ$\text{}_{i}$ ≡ δ T$\text{}_{c}$/δ X$\text{}_{i}$) is determined as -7 and -11 K kbar$\text{}^{-1}$ for the b- and c-axes, respectively. It was found that uniaxial pressure increases the phase transition diffuseness and the tricritical point cannot be achieved for this pyroelectric and ferroelectric single crystal.