Pyroelectric properties of potassium and rubidium titanyl-arsenate single crystals in the temperature range of 4.2-300 K

The temperature dependences of the pyroelectric coefficients of KTiOAsO₄ and RbTiOAsO₄ single crystals grown by flux crystallization have been investigated in the temperature range of 4.2-300 K. With an increase in temperature, superionic conductivity first arises in KTiOAsO₄ (at T > 200 K) and then (at T > 270 K) in RbTiOAsO₄. This conductivity is much higher in the samples polarized at T = 4.2 K. An exponential change in the crystal resistivity along the polar direction is simultaneously observed. The results of measurements in the range of 4.2-200 K indicate larger values of pyroelectric coefficients when compared with potassium and rubidium titanyl-phosphate crystals. A correlation between the pyroelectric coefficients and a change in the lattice constants at isomorphic substitutions of K atoms for Rb and P atoms for As has been revealed within the symmetry approach.