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Investigation of a new lead-free Bi0.5(Na0.40K0.10)TiO3-(Ba0.7Sr0.3)TiO3 piezoelectric ceramic.

Jaita P, Watcharapasorn A, Jiansirisomboon S - Nanoscale Res Lett (2012)

Bottom Line: 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, εr (1,609), and piezoelectric coefficient, d33 (214 pC/N), were obtained at an optimal composition of x = 0.10.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai, 50200, Thailand. sukanda@chiangmai.ac.th.

ABSTRACT
Lead-free piezoelectric compositions of the (1-x)Bi0.5(Na0.40K0.10)TiO3-x(Ba0.7Sr0.3)TiO3 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 (Ba0.7Sr0.3)TiO3 [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, εr (1,609), and piezoelectric coefficient, d33 (214 pC/N), were obtained at an optimal composition of x = 0.10.

No MeSH data available.


Related in: MedlinePlus

Plots of temperature dependence on dielectric constant and dielectric loss. The measurement was done at a frequency of 10 kHz for BNKT-BST ceramics and sintered at 1,125°C.
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Figure 4: Plots of temperature dependence on dielectric constant and dielectric loss. The measurement was done at a frequency of 10 kHz for BNKT-BST ceramics and sintered at 1,125°C.

Mentions: Dielectric constant and dielectric loss of (1-x)BNKT-xBST ceramics were plotted as a function of temperature shown in Figure 4. At Tc, the highest εr of 5,006 was observed in pure BNKT. For BST-added samples, the maximum εr of 4,921 was observed in BNKT-0.10BST ceramic. Since the crystalline structure of BNKT-0.10BST was considered to be near optimum composition having a comparable coexistence of rhombohedral and tetragonal phases, the increase in εr would be expected. The Tc of pure BNKT was found to be 320°C. It has been shown that an A-site isovalent additive had the effect of lowering the Tc [11]. BST is virtually an A-site isovalent additive in which Ba0.7Sr0.3 has an effective charge of +2, which is the same as +2 of Bi0.5(Na0.40K0.10). Moreover, BST has a much lower Tc (approximately 42°C) [12] compared with BNKT; a reduction of Tc was observed in our system. At room temperature, εr of pure BNKT was found to be 1,419. The addition of 10 mol% BST showed an optimum εr of 1,609. As free energy of the rhombohedral phase was close to that of the tetragonal phase, these two phases existing at the BNKT-0.10BST composition easily changed to each other when an electric field was applied. This helped promote the movement and polarization of ferroelectric active ions, leading to the increase of εr [13]. With a further increasing BST, a slight decrease in εr was observed. Phase analysis using XRD patterns indicated that the compositions slightly deviated from the optimal composition, and hence, the lowering of εr values in our samples seemed reasonable.


Investigation of a new lead-free Bi0.5(Na0.40K0.10)TiO3-(Ba0.7Sr0.3)TiO3 piezoelectric ceramic.

Jaita P, Watcharapasorn A, Jiansirisomboon S - Nanoscale Res Lett (2012)

Plots of temperature dependence on dielectric constant and dielectric loss. The measurement was done at a frequency of 10 kHz for BNKT-BST ceramics and sintered at 1,125°C.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3275540&req=5

Figure 4: Plots of temperature dependence on dielectric constant and dielectric loss. The measurement was done at a frequency of 10 kHz for BNKT-BST ceramics and sintered at 1,125°C.
Mentions: Dielectric constant and dielectric loss of (1-x)BNKT-xBST ceramics were plotted as a function of temperature shown in Figure 4. At Tc, the highest εr of 5,006 was observed in pure BNKT. For BST-added samples, the maximum εr of 4,921 was observed in BNKT-0.10BST ceramic. Since the crystalline structure of BNKT-0.10BST was considered to be near optimum composition having a comparable coexistence of rhombohedral and tetragonal phases, the increase in εr would be expected. The Tc of pure BNKT was found to be 320°C. It has been shown that an A-site isovalent additive had the effect of lowering the Tc [11]. BST is virtually an A-site isovalent additive in which Ba0.7Sr0.3 has an effective charge of +2, which is the same as +2 of Bi0.5(Na0.40K0.10). Moreover, BST has a much lower Tc (approximately 42°C) [12] compared with BNKT; a reduction of Tc was observed in our system. At room temperature, εr of pure BNKT was found to be 1,419. The addition of 10 mol% BST showed an optimum εr of 1,609. As free energy of the rhombohedral phase was close to that of the tetragonal phase, these two phases existing at the BNKT-0.10BST composition easily changed to each other when an electric field was applied. This helped promote the movement and polarization of ferroelectric active ions, leading to the increase of εr [13]. With a further increasing BST, a slight decrease in εr was observed. Phase analysis using XRD patterns indicated that the compositions slightly deviated from the optimal composition, and hence, the lowering of εr values in our samples seemed reasonable.

Bottom Line: 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, εr (1,609), and piezoelectric coefficient, d33 (214 pC/N), were obtained at an optimal composition of x = 0.10.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai, 50200, Thailand. sukanda@chiangmai.ac.th.

ABSTRACT
Lead-free piezoelectric compositions of the (1-x)Bi0.5(Na0.40K0.10)TiO3-x(Ba0.7Sr0.3)TiO3 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 (Ba0.7Sr0.3)TiO3 [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, εr (1,609), and piezoelectric coefficient, d33 (214 pC/N), were obtained at an optimal composition of x = 0.10.

No MeSH data available.


Related in: MedlinePlus