Effects of addition of BiFeO3 on phase transition and dielectric properties of BaTiO3 ceramics

Abstract

Samples of xBiFeO 3 -(1 -x)BaTiO 3 (x = 0, 0.02, 0.04, 0.06, 0.07 and 0.08) were synthesized by solid state reaction technique and sintered in air in the temperature range 1,220-1,280°C for 4 h. X-ray diffraction data showed that 2-8 mol% BiFeO 3 can dissolve into the lattice of BaTiO 3 and form single perovskite phase. The crystal structure changes from tetragonal to cubic phase at room temperature when 8 mol% of BiFeO 3 was added into BaTiO 3 . Scanning electron microscope images indicated that the ceramics have compact and uniform microstructures, and the grain size of the ceramics decreases with the increase of BiFeO 3 content. Dielectric constants were measured as functions of temperatures (25-200°C). With rising addition of BiFeO 3 , the Curie temperature decreases. For the sample with x = 0.08, the phase transition occurred below room temperature. The boundary between tetragonal and cubic phase of the BiFeO 3 -BaTiO 3 system at room temperature locates at a composition between 7 and 8 mol% of BiFeO 3 . The diffusivity parameter c for compositions x = 0.02 and x = 0.07 is 1.21 and 1.29, respectively. The relaxor-like behaviour is enhanced by the BiFeO 3 addition.

Structural phase boundary of BiFeO3–Bi(Zn1/2Ti1/2)O3–BaTiO3 lead-free ceramics and their piezoelectric properties

“…0.1 wt% MnO 2 and BF65-BZT5-BT30 ? 1 mol% MnO 2 ceramics, d 33 , e 33 T /e 0 and tand recorded in BF72.5-BT27.5 [21] and BF70-BT30 [17] ceramics were also presented in Fig. 4.…”

“…It is known that BiFeO 3 is crystallized in rhombohedral lattice structure while BF-xBT solid solution undergoes a phase transition from rhombohedral to pseudocubic at BT content of x = 0.33 [16,17] or x = 0.275 [21]. For this composition-induced rhombohedral-pseudocubic structural phase [16,17,20,21,24,25,[33][34][35][36][37] respectively. The dot lines stand for structural phase boundaries separating rhombohedral (R), pseudocubic, and tetragonal (T) phase while the solid line stands for structural phase boundary between rhombohedral and pseudocubic observed in the fine-grained ceramics.…”

“…Their piezoelectric constants d 33 , dielectric constant e 33 T /e 0 and loss tand were measured at room temperature after aging 24 h and presented in Fig. 4, respectively, as a function of BT content and BZT content.…”

“…0.1 wt% MnO 2 [20] and BF65-BZT5-BT30 ? 1 mol% MnO 2 [24] ceramics, d 33 , e 33 T /e 0 and tand data for BF70-BT30 [17] and BF72.5-BT27.5 [21] ceramics are also plotted here for comparison. Segments only for view was obtained for BF65-BZT10-BT25 ?…”

“…Meanwhile, a maximum piezoelectric property of d 33 = 124 pC/N, e 33 T / e 0 = 760, tand = 0.078, and k p = 0.29 was reported in the 0.725BF-0.275BT ceramics with composition at structural phase boundary between rhombohedral and pseudocubic [21]. Even though using Mn-doping strategy and optimizing solid state electroceramic processing have made a great progress to decrease dielectric loss, BF-BT ceramics reported so far is still far away from practical level of tand B0.02.…”