Papers by Keyword: Poling

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Authors: Chun Huy Wang
Abstract: Extending the investigations on (Na0.5K0.5)NbO3-based solid solution for lead-free piezoelectric ceramics, this paper consider the complex solid-solution system (Na0.5K0.5)NbO3–Bi0.5(Na0.85K0.15)0.5TiO3 [NKN-BNKT]. (Na0.5K0.5)NbO3 with 2 ~ 6 mol% Bi0.5(Na0.85K0.15)0.5TiO3 has been prepared following the conventional mixed oxide process. A morphotropic phase boundary (MPB) between orthorhombic (O) and hexagonal (H) was found at the composition 0.96NKN-0.04BNKT with correspondingly enhanced dielectric and piezoelectric properties. The electromechanical coupling factor and dielectric constant are higher for compositions near the MPB. The dielectric constant (KT33), planar coupling coefficient (kp) and thickness coupling coefficient (kt)of 0.96NKN-0.04BNKT ceramics were 1273, 34% and 38%, respectively.
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Authors: Chun Huy Wang
Abstract: PbZrO3-PbTiO3 (PZT)-based ceramics are playing a dominant role in piezoelectric materials, their evaporation of harmful lead oxide during the sintering process causes a crucial environment problem. It is necessary to search for lead-free piezoelectric materials that have such excellent properties as those found in the PZT-based ceramics. Therefore (Na0.5K0.5)NbO3-based solid solutions were studied to improve piezoelectric properties. In the present study, various quantities of Bi2O3 were added into 0.98(Na0.5K0.5)NbO3-0.02Ba(Sn0.02Ti0.98)O3 (0.98NKN-0.02BST) ceramics. It was found that 0.98NKN-0.02BST with the addition of 0~4.0 wt.% Bi2O3 exhibit relatively good piezoelectric properties. For 0.98NKN-0.02BST ceramic with the addition of 1.0 wt.% Bi2O3, the electromechanical coupling coefficients of the planar mode kp and the thickness mode kt reach 0.21 and 0.46, respectively, at the sintering of 1100oC for 3 h. The ratio of thickness coupling coefficient to planar coupling coefficient is 2.2. It is obvious that 0.98NKN-0.02BST solid solution ceramic by adding low quantities of Bi2O3 is one of the promising lead-free ceramics for high frequency electromechanical transducer applications.
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Authors: Chun Huy Wang
Abstract: In the present study, various quantities of Bi2O3 were added into 0.98(Na0.5K0.5)NbO3-0.02Bi(Na0.93K0.07)TiO3 (0.98NKN-0.02BNKT) ceramics. It was found that 0.98NKN-0.02BNKT with the addition of 0~0.5 wt.% Bi2O3 exhibit relatively good piezoelectric properties. For 0.98NKN-0.02BNKT ceramics, the electromechanical coupling coefficients of the planar mode kp and the thickness mode kt reach 0.40 and 0.47,respectively. For 0.98NKN-0.02BNKT ceramics with the addition of 0.3 wt.% Bi2O3, the electromechanical coupling coefficients ofthe planar mode kp and the thickness mode kt reach 0.50 and 0.53, respectively. It is obvious that 0.98NKN-0.02BNKT solid solution ceramics by adding low quantities of Bi2O3 is one of the promising lead-free ceramics for electromechanical transducer applications.
3
Authors: Chun Huy Wang
Abstract: In the present study, various quantities of Bi2O3 were added into 0.98(Na0.5Bi0.5)TiO3 -0.02Ba(Sn0.08Ti0.92)O3 (0.98NBT-0.02BST) ceramics. High-density samples were obtained through the addition of Bi2O3 into 0.98NBT-0.02BST ceramic. It was found that 0.98NBT-0.02BST with the addition of 0~3.0 wt.% Bi2O3 exhibit relatively good piezoelectric properties. For 0.98NBT-0.02BST ceramic with the addition of 2 wt.% Bi2O3, the electromechanical coupling coefficients of the planar mode kp and the thickness mode kt reach 0.12 and 0.61, respectively, at the sintering of 1100oC for 3 h. The ratio of thickness coupling coefficient to planar coupling coefficient is 5.1. It is obvious that 0.98NBT-0.02BST solid solution ceramic by adding low quantities of Bi2O3 is one of the promising lead-free ceramics for high frequency electromechanical transducer applications.
1051
Authors: Chun Huy Wang
Abstract: In this paper, the effects of Bi2O3 addition on the electrical and physical properties of 0.98(Na0.5K0.5)NbO3-0.02(Na0.5Bi0.5)TiO3 were investigated. The 0.98(Na0.5K0.5)NbO3 -0.02(Na0.5Bi0.5)TiO3 [0.98NKN-0.02NBT] ceramics with the addition of 0~0.5 wt% Bi2O3 have been prepared following the conventional mixed oxide process. X-ray diffraction analysis revealed that, during sintering, all of the (Na0.5Bi0.5)TiO3 diffuse into the lattice of ((Na0.5Bi0.5))NbO3 to form a solid solution, in which a orthorhombic phase with a perovskite structure was found. For 0.98NKN-0.02NBT ceramics by doping 0.1 wt% Bi2O3, the poled dielectric constant (K33T) and the electromechanical coupling coefficients of the planar mode kp reach 684 and 0.38, respectively, after sintering at 1100 °C for 3 h. Our results show that 0.98NKN-0.02NBT with the addition of 0.1 wt% Bi2O3 is a good lead-free piezoelectric ceramic.
1250
Authors: Chun Huy Wang
Abstract: In this paper, the effects of Bi2O3 addition on the electrical and physical properties of 0.98(Na0.5K0.5)NbO3-0.02(Na0.5Bi0.5)TiO3 were investigated. The 0.98(Na0.5K0.5)NbO3 -0.02(Na0.5Bi0.5)TiO3 [0.98NKN-0.02NBT] ceramics with the addition of 0~0.5 wt% Bi2O3 have been prepared following the conventional mixed oxide process. X-ray diffraction analysis revealed that, during sintering, all of the (Na0.5Bi0.5)TiO3 diffuse into the lattice of (Na0.5K0.5)NbO3 to form a solid solution, in which a orthorhombic phase with a perovskite structure was found. For 0.98NKN-0.02NBT ceramics by doping 0.1 wt% Bi2O3, the poled dielectric constant (K33T) and the electromechanical coupling coefficients of the planar mode kp reach 684 and 0.38, respectively, after sintering at 1100 °C for 3 h. Our results show that 0.98NKN-0.02NBT with the addition of 0.1 wt% Bi2O3 is a good lead-free piezoelectric ceramic.
95
Authors: Chun Huy Wang
Abstract: K2CO3-doped 0.98(Na0.5K0.5)NbO3-0.02(Na0.5Bi0.5)TiO3 [abbreviated as 0.98NKN-0.02NBT] lead-free piezoelectric ceramics were prepared by the conventional mixed oxide process. The effects of K2CO3 additions on the crystalline structures and electrical properties of the 0.98NKN-0.02NBT ceramics were investigated. The specimens of 0.98NKN-0.02NBT ceramics added with K2CO3 maintain an orthorhombic phase. In the case of low K2CO3 content (≤ 0.3 wt%), the grain growth became remarkable. The increase of grain size favors improving the piezoelectric properties, which is known as grain size effect. The grain size effect compensates the decrease of the electromechanical coupling factor due to the hard doping effect. For 0.98NKN-0.02NBT ceramics by doping 0.3 wt% Na2CO3, the electromechanical coupling coefficients of the thickness mode kt and the planar mode kp reach 0.51 and 0.33, respectively, after sintering at 1100 oC for 3 h. Our results show that 0.98NKN-0.02NBT with the addition of 0.3 wt% K2CO3 is a good lead-free piezoelectric ceramic.
83
Authors: Chun Huy Wang
Abstract: Lead free piezoelectric ceramics 0.98(Na0.5K0.5)NbO3-0.02(Na0.5Bi0.5)TiO3 [abbreviated as 0.98NKN-0.02NB with the addition of 0~1.0 wt% Na2CO3 have been synthesized by the conventional mixed oxide process. The effects of amount of Na2CO3-content on the electrical properties and crystalline structures were investigated. The specimens of 0.98NKN-0.02NBT ceramics added with Na2CO3 maintain an orthorhombic phase. In the case of low Na2CO3 content ( 0.3 wt%), the grain growth became remarkable. The increase of grain size favors improving the piezoelectric properties, which is known as grain size effect. The grain size effect compensates the decrease of the electromechanical coupling factor due to the hard doping effect. For 0.98NKN-0.02NBT ceramics by doping 0.3 wt% Na2CO3, the electromechanical coupling coefficients of the thickness mode kt and the planar mode kp reach 0.51 and 0.33, respectively, after sintering at 1100 °C for 3 h. Moreover, the addition of excess Na2CO3 is a helpful method on ceramic processing to improve the dielectric tangent loss and the mechanical quality factor. Our results show that 0.98NKN-0.02NBT with the addition of 0.3 wt% Na2CO3 is a good lead-free piezoelectric ceramic.
113
Authors: Chun Huy Wang
Abstract: In this paper, the effects of Nb2O5 addition on the electrical and physical properties of 0.98(Na0.5K0.5)NbO3-0.02(Na0.5Bi0.5)TiO3 were investigated. The 0.98(Na0.5K0.5)NbO3-0.02(Na0.5 Bi0.5)TiO3 [0.98NKN-0.02NBT] ceramics with the addition of 0~1.5 wt% Nb2O5 have been prepared following the conventional mixed oxide process. X-ray diffraction analysis revealed that, during sintering, all of the (Na0.5Bi0.5)TiO3 diffuse into the lattice of (Na0.5K0.5)NbO3 to form a solid solution, in which an orthorhombic phase with a perovskite structure was found. For 0.98NKN-0.02NBT ceramics by doping 0.3 wt% Nb2O5, the poled dielectric constant (K33T) is 1180. The electromechanical coupling coefficients of the planar mode kp and the thickness mode kt reach 0.43 and 0.52, respectively. Our results show that 0.98NKN-0.02NBT with the addition of 0.3 wt% Nb2O5 is a good lead-free piezoelectric ceramic.
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