The dielectric, ferroelectric and pyroelectric properties of Li0.025Na0.975NbO3 crystals grown by the Czochralski technique have been investigated in the temperature range of 20 K to 300 K. The anomalies of the dielectric constant, electric polarization and pyroelectric properties indicate the existence of a low temperature phase transition. It occurs at about 180 K on cooling and at about 260 K on heating, wit an extraordinary large thermal hysteresis of about 80 K. The room temperature structure of the crystal has been determined and the possible point groups of the low temperature phes deduced. The time response of the pyrocle-ctric charge has been observed. A peculiar new phenomenon that the pyroelectric charge changes its polarity with time is reported. It is attributed to the coexistence of two phases in the process of phase transition.