Guoxi Jin

Structural and Multiferroic Properties of 1-x(Bi0.85La0.15)FeO3–xPbTiO3 Solid Solutions

A series of solid solutions of 1-x(Bi0.85La0.15)FeO3–xPbTiO3 for x = 0.35, 0.4, 0.415, 0.43, 0.45, 0.47)(BLFPT) are prepared by the mixed oxide method. The X-ray diffraction analysis shows that BLF-PT has a single perovskite phase with mixed tetragonal and rhombohedral phases in x = 0.415. The dielectric constant and Curie temperature of BLF-PT for x = 0.415 is 836 at 102 Hz and 419 °C, respectively. The remnant polarization and magnetization of x = 0.415 reach 39 μC/cm2 and 0.03 emu/g, showing a coexistence of ferroelectricity and ferromagnetism in the vicinity of the morphotropic phase boundary. The structure refinement is used to explain the correlation between structural and multiferroic properties of BLFPT solid solutions, which may be due to the existence of the monoclinic and orthorhombic phases lies on both sides of morphotropic phase boundary.

Properties of compositionally graded (1−x)(Bi0.85La0.15)FeO3-xPbTiO3 ceramics fabricated by tape casting

Three types of (1−x)(Bi0.85La0.15)FeO3-xPbTiO3 (BLF–PT) compositionally graded ceramics (x = 0.38, 0.40, 0.415 and 0.43) were fabricated using a lamination process based on the non-aqueous tape casting method. Scanning electron microscope images showed that the compositionally graded ceramics possessed dense microstructures without obvious cracks. The dielectric, ferroelectric and piezoelectric properties of the BLF–PT ceramics were sensitive to the composition distributions in the thickness direction. The BLF–PT ceramics with monotonic variation of PT content (in the thickness direction) exhibited the best piezoelectric properties. The tip displacement of compositionally graded piezoelectric ceramics reached up to ~13.5 μm, which is about ten times higher than that of BLF–PT ceramics with single composition.

High temperature “Hard” piezoelectric ceramics of BiScO 3 -PbTiO 3 -Pb(Nb, Mn)O 3 with Fe 2 O 3 addition

“Hard” piezoelectric materials of Fe modified 0.37BiScO₃-0.6PbTiO₃-0.03Pb(Mn_1/3Nb_2/3)O₃ (BS-PT-PMN-Fe) ceramics were prepared by traditional solid state reaction method. X-ray diffraction (XRD) analysis revealed that BS-PT-PMN-Fe ceramics showed single perovskite structure with dominant tetragonal phase, and the c/a ratios was enlarged with Fe content. The grain size of BS-PT-PMN-Fe ceramics decreased obviously from 25 to 1 μm with the increase of Fe content from 0 to 3 mol%. The dielectric and piezoelectric properties of BS-PT-PMN-Fe ceramics with 2 mol% Fe addition are as follows: ε = 600, tanδ = 0.008, d₃₃ = 240, Q_m = 500, and k_p = 0.38, which were comparable to those of PZT-4 traditional “hard” piezoelectric ceramics. Both piezoelectric and dielectric properties were stable from room temperature up to 400 °C, about 250 °C higher than those of conventional PZT piezoelectric ceramics. In addition, the temperature coefficient of resonance frequency (TCF) of ceramics with 3 mol% Fe addition was -21 ppm/°C, which is one tenth that of PZT ceramics.

Enhanced piezoelectric properties of 0.60 BiFeO 3 -0.35 PbTiO 3 -0.05 Pb(Zn 1/3 Nb 2/3 )O 3 ceramics for high temperature applications

A series of solid solutions 0.60 BiFeO3-0.35 PbTiO3-0.05 Pb(Zn1/3Nb2/3)O3 (0.60BF-0.35PT-0.05PZN) were fabricated by solid state reaction method. This ternary system possessed the coexistence of both rhombohedral (R3c) and tetragonal (P4mm) phase. The 0.60BF-0.35PT-0.05PZN ceramics were mechanically and electrically robust and can be poled to obtain a high piezoelectricity. Sintering temperature had a strong influence on the structures and properties. The rhombohedral phase decreased with the increase of sintering temperature, which indicated the rhombohedral phase is metastability. The specimens exhibited the best dielectric and piezoelectric properties at sintering temperature of 1020 °C. After quenching at 650 °C, the content of tetragonal phase reduced, the dielectric constant increased, the piezoelectric constant d33 could be enhanced from 55 pC/N to 65 pC/N. In addition, the temperature stability of the ternary ceramic was also improved. The enhanced piezoelectric properties and high Curie temperature indicated that BF-PT-PZN ceramics were one of promising candidates for high temperature piezoelectric applications.

Processing optimization and field-induced strain response in laminated 0.6(Bi 0.85 La 0.15 ) FeO 3 -0.4PbTiO 3 ceramics

0.6(Bi0.85La0.15)FeO3-0.4PbTiO3 (BLF-PT) ceramics with pure perovskite structure were produced and laminated from a non-aqueous tape casting method. The effects of pressure and temperature, during the tapes lamination process, on the bulk density, ferroelectric and piezoelectric properties of BLF-PT ceramics were systematically investigated. The field-induced strain level and remnant polarization Pr of the laminated BLF-PT ceramics increased while the dielectric loss tan δ decreased with the rising of lamination temperature from 30 to 90 °C due to the stronger combination between the ceramic tapes and relative higher bulk density. On the contrary, with the rising of lamination pressure from 30 to 150 MPa, The field-induced strain level and Pr first increased and then decreased. The dielectric constant and loss, remnant polarization, strain, and high field piezoelectric constant of BLF-PT ceramics obtained under optimal conditions are 409, 1.4 % at 1 kHz, 33 μC/cm20.07 % and 141 pm/V (Smax/Emax) at 50kV/cm, respectively. The results show that the laminated ceramics derived from tapes casting method exhibit comparable dielectric, ferroelectric and piezoelectric properties to those prepared by conventional powder forming technique, which is the basic step for the continuous developing for piezoelectric devices with multilayered or graded structure.