Development of electrical properties in lead-free bismuth sodium lanthanum titanate–barium titanate ceramic near the morphotropic phase boundary (original) (raw)
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Journal of Electroceramics, 2006
The important properties of lead-free piezoelectric ceramics have been investigated from Bismuth Sodium Lanthanum Titanate and Barium Titanate system: (1 − y)(Bi 0.5 Na 0.5 ) (1−1.5x) La x TiO 3 (BNLT)-yBaTiO 3 (BT) where x = 0.017 and y = 0 − 0.2, respectively. The morphotropic phase boundary (MPB) was found to be around y = 0.1 by the x-ray diffraction and dielectric measurement at various amount of BT. The temperature dependence of dielectric constant (ε r ) at various value of y showed the diffuse phase transition exhibiting the relaxor type ferroelectrics. The degree of diffuseness increased at a high doping content of about y = 0.15 where the second phase transition (T 2 ) of the ferroelectric to antiferroelectric phase disappeared. Moreover, this sample had the maximum piezoelectric coefficient (d 33 ) of about 112 pC/N with relatively low dielectric constant. The optimum sintering temperatures and the microstructures of the dense BNLT-BT ceramics were also examined.
Investigation of a new lead-free Bi0.5(Na0.40K0.10)TiO3-(Ba0.7Sr0.3)TiO3 piezoelectric ceramic
Nanoscale Research Letters, 2012
Lead-free piezoelectric compositions of the (1-x)Bi 0.5 (Na 0.40 K 0.10 )TiO 3 -x(Ba 0.7 Sr 0.3 )TiO 3 system (when x = 0, 0.05, 0.10, 0.15, and 0.20) were fabricated using a solid-state mixed oxide method and sintered between 1,050°C and 1,175°C for 2 h. The effect of (Ba 0.7 Sr 0.3 )TiO 3 [BST] content on phase, microstructure, and electrical properties was investigated. The optimum sintering temperature was 1,125°C at which all compositions had densities of at least 98% of their theoretical values. X-ray diffraction patterns that showed tetragonality were increased with the increasing BST. Scanning electron micrographs showed a slight reduction of grain size when BST was added. The addition of BST was also found to improve the dielectric and piezoelectric properties of the BNKT ceramic. A large room-temperature dielectric constant, ε r (1,609), and piezoelectric coefficient, d 33 (214 pC/N), were obtained at an optimal composition of x = 0.10.
IOP Conference Series: Materials Science and Engineering, 2011
Ferroelectric ceramics with formula (Bi 0.487 Na 0.487 La 0.017 )TiO 3 /xPb(Zr 0.52 Ti 0.48 )O 3 (when x = 0, 0.1, 0.5, 1.0 and 3.0 wt%) were prepared by solid-state mixed-oxide method and sintered at 1050 -1200°C for 2 h. The optimum sintering temperature was 1100°C at which all samples had the density at least 98% of theoretical values. X-ray diffraction results suggested that addition of PZT did not significantly affect unit cell of BNLT. An addition of PZT into BNLT effectively increased density and reduced grain size of the ceramics. These changes played an important role on mechanical properties improvement. Room temperature dielectric constant increased with increasing PZT concentration. The addition of PZT into BNLT slightly degraded ferroelectric properties, but improved the piezoelectric properties.
Journal of Electroceramics, 2013
In this paper, lead-free (1-x)(Bi 0.5 Na 0.5 ) 0.94 Ba 0.06-TiO 3 -xBiAlO 3 (BNBT-BA, x00, 0.010, 0.015, 0.020, 0.025, and 0.030) piezoelectric ceramics were synthesized using a conventional solid-state reaction method. The effect of BiAlO 3 concentration on dielectric, ferroelectric and piezoelectric properties were investigated. The ferroelectric and piezoelectric properties of BNBT ceramics are significantly influenced by the presence of BA. In the composition range studied, X-ray diffraction revealed a perovskite phase with the coexistence of rhombohedral and tetragonal phases. The temperature dependence of dielectric properties showed that the depolarization temperature (T d ) shifted towards lower temperatures and that the degree of diffuseness of the phase transition around T d and T m became more obvious with increasing BiAlO 3 content. The remanent polarization increased with increasing BA, and reached a maximum value of 30 μC/cm 2 at x00.020. As a result, at x00.020, the piezoelectric constant (d 33 ) and the electromechanical coupling factor (k p ) of the ceramics attained maximum values of 188 pC/N and 34.4 %, respectively. These results indicate that BNBT-BA ceramics is a promising candidate for leadfree piezoelectric materials.
Japanese Journal of Applied Physics, 2006
A lead-free barium titanate (BaTiO 3 ) ceramics with a high density and a large piezoelectric constant, d 33 , as manufactured at 1320 C by microwave sintering, using a pure fine powder with a particle size of 100 nm produced by hydrothermal synthesis. The density of the ceramic with a 3.4 mm grain size was more than 98.3% of the theoretical value. The ceramic after poling had a dielectric constant of " T 33 =" 0 ¼ 4200, an electromechanical coupling factor planar mode of k p ¼ 36% and d 33 ¼ 350 pC/ N. The value of d 33 is the largest one ever reported for lead-free BaTiO 3 ceramics.
Journal of Sol-Gel Science and Technology, 2019
In this work, lead-free 0.965Bi 0.5 Na 0.5 TiO 3-0.035BaTiO 3 (BNT-BT) piezoelectric ceramics were synthesized by a sol-gel process. X-ray diffraction pattern of the BNT-BT samples revealed that powder calcined at 600°C, exhibit a pure perovskite structure. Scanning electron microscopy (SEM) was used to find the surface morphology and grain size of the investigated ceramics. At an optimized sintering temperature of 1150°C, well-saturated ferroelectric (P-E) hysteresis loops with high remnant polarization (P r = 34.8 µC/cm 2) and low corrosive field (E c = 23 kV/cm) were obtained. Electric field-induced strain of 0.137% with a dynamic piezoelectric coefficient (d 33 * = 196 pm/V) was observed under 75 kV/cm drawing field. In addition, high static piezoelectric constant (d 33 = 138 pC/N) was recorded for the sample sintered at 1150°C. This value of d 33 is comparable to that of BNT-based bulk piezoelectric ceramics.
Current Applied Physics, 2012
a b s t r a c t (Bi 0.5 Na 0.5 )TiO 3 was doped in situ with 5, 8, and 11 mol% BaTiO 3 (BNT-BT x ; x ¼ 0.05, 0.08 and 0.11) using a sol-gel technique. The resulting powders from gel precursors showed microstructures consisting of nano-sized grains and crystalline perovskite structure. Spark plasma sintering (SPS) technique was used to prepare high densified (98e99%r theor ) BNT-BT x ceramics from these nanopowders. The results confirm the spark plasma sintering method applied to nano-scale powders, obtained by sol-gel, as a viable route in producing nanostructured ceramics. The evolution of the structure and electrical properties of the ceramics with BaTiO 3 concentration (x) was investigated. The permittivity of BNT-BT 0.08 ceramic is higher (ε r ¼ 2090, at 100 kHz) than that for x ¼ 0.05 (ε r ¼ 1350) and x ¼ 0.11 (ε r ¼ 1800). BNT-BT 0.08 ceramic shows maximum values for the frequency constants (N p , N t ), piezoelectric charge coefficient (d 31 ) and piezoelectric voltage coefficient (g 31 ), and minimum values for the electromechanical coupling factor (k p ) and piezoelectric charge coefficient (d 33 ). The electrical properties of these ceramics are influenced by grains size, oxygen deficiency and non-uniform internal stresses due to these oxygen deficiencies. BNT-BT x ceramics sintered by SPS seem to be good ceramic resonators with high mechanical quality factor (Q m ).
Materials Science-poland, 2011
The 0.935(Bi0.5Na0.5) TiO3 -0.065BaTiO3 (abbreviated as BNT6.5BT) lead-free ceramics were prepared by conventional solid state sintering technique. The effects of sintering temperature (1150–1200 °C) and poling condition on its piezoelectric properties were examined. Piezoelectric properties like the piezoelectric constant (d33) and electromechanical factors (kp , kt ) depend on the poling field and poling temperature, whereas different poling times, in the 5–30 min range, were not observed to have any significant effect on the piezoelectric properties. With respect to piezoelectric properties, the chosen sintering temperature range is suitable for BNT6.5BT ceramics.
Journal of Materials Science, 2013
Ferroelectric (K 0.455 Li 0.045 Na 0.5)(Nb 0.9 Ta 0.1)O 3 ? x mol% BaCO 3 ceramic compositions with Ba 2? as an A-site dopant in the range of x = 0-1.2 mol% were synthesized by conventional ceramic processing route. Effect of Ba 2? content on the microstructure, ferroelectric, dielectric, and piezoelectric properties of the ceramics was investigated. The results of X-ray diffraction reveal that Ba 2? diffuse into the (K 0.455 Li 0.045 Na 0.5)(Nb 0.9 Ta 0.1)O 3 lattices to form a solid solution with a perovskite structure having typical orthorhombic symmetry. As Ba 2? content increases, cell volume and tetragonality increase in the crystal structure of the ceramics. Increasing doping level of Ba 2? inhibits grain growth in the ceramics and reduces both the Curie temperature (T c) and tetragonal-orthorhombic phase transition temperature (T o-t). The bulk density, remnant polarization P r , room-temperature dielectric constant (e 0 RT), planar electromechanical coupling factor k p , and piezoelectric charge coefficient d 33 are found to increase as Ba 2? concentration increases from 0 to 0.8 mol% and then decrease as Ba 2? content increases further from 0.8 to 1.2 mol%. High piezoelectric properties of d 33 = 187 pC/N and k p = 48 % are found in 0.8 mol% Ba 2? composition. Optimum amount of Ba 2? dopant takes the polymorphic phase boundary region consisting of orthorhombic and tetragonal crystal structures of the ceramic system near the room temperature and enhances its piezoelectric properties.