Second harmonic generation and temperature autostabilized nonlinear dielectric element (TANDEL) effect have been studied for ferroelectric solid solutions (Na_xK_1−x)VO₃ and (Na_xLi_1−x)VO₃ in the vicinity of the Curie temperature. The generated second harmonic is linear for low biasing d.c. fields with zero off-set. The deviations from linear behaviour and a sharp decrease in the amplitude of second harmonic is observed at higher d.c. bias voltages. The TANDEL elements, in the autostabilized state, adjust their impedance against the variation of applied a.c. voltage. The observed zero off-set might be due to the presence of defects which give internal bias and generate second harmonic.

Pyroelectric properties of poled solid solutions of lead-barium titanate and leadstrontium titanate have been investigated in the temperature range covering their transition points. The values of pyroelectric current and coefficients of (Pb_x − Ba_{1 −x})TiO₃ and (Pb_x − Sr_{1 −x})TiO₃(x = 0·8 − 0·5) show a sharp peak at the Curie temperature. It is observed that these values change with Ba or Sr concentration in the respective solid solutions.

The d.c. electrical conductivity of sodium vanadate, potassium vanadate, lithium vanadate and their solid solutions sodium-potassium vanadate, sodium-lithium vanadate were measured by a two-probe method in the temperature range covering their transition points. These materials show sharp change in conductivity at their phase transition temperatures. In sodium, potassium and lithium vanadates an exponential increase in d.c. conductivity is observed in ferroelectric region while discontinuities are observed above the transition temperatures. The activation energy in paraelectric state of the solid solutions is found to be higher than in ferroelectric state. In solid solutions the activation energy depends upon sodium vanadate concentration.

The d.c. electric field effect on ferroelectric triglycine sulphate (TGS) and TGS-Se crystals at high temperature above the Curie temperature shows the formation of a solid state battery. The current and the electromotive force of the battery are measured and their changes observed near the Curie temperature. Even if the electrodes are short-circuited the emf recovers almost to the same value.

Pyroelectric properties of Gd-doped and undoped potassium vanadate and lithium vanadate investigated in the temperature range covering their transition points show sharp increase at Curie temperature for undoped and for 0·025, 0·05, 0·1 mol% Gd₂O₃-doped, but no remarkable peak at Curie temperature for 0·5, 1, 3 mol% Gd₂O₃-doped KVO₃ and LiVO₃. The Curie temperature of all the samples remains the same for various concentrations of Gd.

Dielectric hysteresis properties of undoped and dysprosium-doped potassium vanadate have been studied in the temperature range covering their transition points. The coercive field of these materials was measured by the hysteresis loop method. It is observed that the coercive field of KVO₃ doped with Dy₂O₃ at different concentrations (0 to 3 mol%) is remarkably dependent on doping concentration. It is also seen that undoped KVO₃ shows ferroelectric behaviour up to 320°C while Dy₂O₃-doped KVO₃ samples show ferroelectric behaviour up to 380°C for all concentrations.

The dielectric hysteresis property of sodium vanadate, rubidium vanadate, cesium vanadate and their solid solutions has been studied in the temperature range covering their transition points. The hysteresis loop method is used for coercive field measurements. It was observed that the coercive field decreases with increasing temperature, and that it also decreases with increasing sodium concentration in the solid solutions (sodium-rubidium) vanadate and (sodium-cesium) vanadate.

The dielectric hysteresis property of undoped and Gd₂O₃-doped potassium vanadate and lithium vanadate has been investigated in the temperature range covering their transition points. The hysteresis loop method has been used for coercive field measurements. The coercive field of Gd₂O₃-doped KVO₃ and LiVO₃ increases for 0·025, 0·05, and 0·1 mol %, however, it decreases for 0·5, 1 and 3 mol % of Gd₂O₃. It was found that the Curie temperatures of KVO₃ and LiVO₃ remain the same for various concentrations of Gd₂O₃.

Measurements of pyroelectric currents and coefficients of poled sintered discs of ferroelectric solid solutions, potassium-cesium vanadate and potassium-lithium vanadate have been investigated in the temperature range covering their transition points. In these solid solutions, K_xCs_1−xVO₃ and K_xLi_1−xVO₃, pronounced peaks have been observed at the ferroelectric curie temperatures. The peak values of pyroelectric currents and coefficients change with change in potassium concentration in both the solid solutions.

The thermoelectric power of the vanadates of potassium, cesium and lithium and their solid solutions was measured in the temperature range covering their transition points. The thermoelectric power measurement was carried out by the two-electrode technique for pellets of polycrystalline ceramic samples. The thermoelectric power increased with temperature initially, then decreased attaining a zero value at the transition temperature. As the concentration of KVO₃ increased the thermoelectric power decreased for the solid solutions (K_x − Cs_1−x)VO₃, whereas the thermoelectric power increased with increase in concentration of KVO₃ for the solid solutions (K_x − Li_1−x)VO₃. Vanadates of potassium, cesium, and lithium and their solid solutions showedP type semiconductor behaviour in ferroelectric state andn type semiconductor behaviour in paraelectric region.

The temperature dependence of dc electrical conductivity was measured by two-probe technique in the vicinity of phase transition point for ferroelectrics sodium vanadate and rubidium vanadate doped with different concentrations of La₂O₃. These materials show a sharp change in conductivity at their phase transition temperatures. The results were found to obey the conventional exponential law and the activation energies were calculated for ferroelectric and paraelectric states. It was found that activation energy in ferroelectric phase is smaller than in the paraelectric phase. The activation energy increases slowly with increase in doping concentration of La₂O₃ up to 0·1 mol%, however, it decreases with further increase in doping concentration, in both ferro and para states. The dc electrical conductivity below the Curie temperature is of mixed type (ionic-electronic) while it is electronic type above the Curie temperature.