**4. Conclusions**

in a decrease of the *Tm* values when the barium concentration increases [22]. The SBBN-50 and SBBN-70 samples have shown a greater increase in the occupancy of Ba2+ and Bi3+ in *A* sites than was observed in the SBBN-30, since the concentration of Ba2+ is higher than that of Bi3+, which explains the decrease of *Tm* from 30 to 70 at% of barium and then by extension the lower

For SBBN-85 and BBN, a greater decrease of the Ba2+ occupancy in *A* sites is observed than in SBBN-70 [22], but the *Tm* values are lower. For both compositions, it has also been reported that there is a higher Ba2+ occupancy in Bi3+ sites than in the other compositions [22]. A higher Ba2+ occupancy in Bi3+ sites and the corresponding generated oxygen vacancies would distort the ionic dipoles due to the *A* sites' ions. Then, the decay of the spontaneous polarization could be affected, providing a decrease of the *Tm* values and the activation energy values for the

For the third contribution, there were not enough experimental points in some compositions. Thus, the activation energy was only estimated for the studied samples, showing values between 0.7 and 1.50 eV. These values are related to electrical conductivity processes, which are governed by double ionized oxygen vacancies [21, 24]. The oxygen vacancies in the structure of the studied samples are generated to compensate the electrical charge unbalance,

Figure 10 shows the temperature dependence of the remanent polarization (*Pr*), which has been obtained from the pyroelectric current dependence *iP*(*T*) using equation 3. It can be noted that there is an important influence of the barium concentration on the *Pr* values. At room temper‐ ature, an increase of *Pr* is observed for the lower barium concentration (x ≤ 30 at%); above 30 at%, *Pr* decreases. These results are in agreement with the *Pr* behaviour, which has previously

which is caused by the substitution of trivalent Bi3+ ion for divalent Ba2+ and Sr2+ ions.

been discussed in relation to the hysteresis loops (*P*-*E* dependence).

**Figure 10.** Temperature dependence of the remanent polarization (*Pr*) for the studied compositions.

activation energy values for the pyroelectric contribution.

98 Ferroelectric Materials – Synthesis and Characterization

thermal depoling process (pyroelectric response).

**3.3. Ferroelectric and pyroelectric parameters**

The ferroelectric properties and thermally stimulated processes were studied in the Sr1 xBaxBi2Nb2O9 ferroelectric ceramic system with x = 0, 15, 30, 50, 70, 85, 100 at%. The dependence of the polarization on the applied electric field was discussed, at room temperature, for normal and relaxor ferroelectric compositions. The Gaussian method was used to separate the pyroelectric contribution from the other contributions to the total i(T) response in the studied samples. Three different contributions were obtained in the studied temperature range. The first contribution was associated with space charge, the second with the pyroelectric current and the third with the electric conductivity processes. The remanent polarization, the pyro‐ electric coefficient and the current response merit figure were evaluated at room temperature. The SBBN-30 showed better ferroelectric and pyroelectric properties.
