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ABSTRACT: Pb(Zr0.53Ti0.47)O3 (PZT) thin films were prepared on La0.5Sr0.5CoO3 (LSCO) coated Si substrates by a sol–gel route. The thickness of LSCO electrode was found to modify the preferential orientation
of PZT thin films, which consequently affected the dielectric and ferroelectric properties. (100) textured PZT films with
dense columnar structure could be obtained on the top of (110) textured LSCO with thickness of 230nm. PZT thin films prepared
on the optimized LSCO films exhibit the enhanced dielectric constant and remnant polarization of 980 and 20μC/cm2, respectively.
Journal of Materials Science Materials in Electronics 04/2012; 21(5):514-518. · 1.08 Impact Factor
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ABSTRACT: Pb0.3Sr0.7TiO3 (PST) thin films were deposited on Pt coated Si (100) substrates by sol–gel techniques using a series of different sol concentrations
(0.15, 0.20, 0.25, 0.30, and 0.40M). Both structural and dielectric characteristics of PST films as a function of the sol
concentration were investigated. PST thin films reveal typical crystalline structure with columnar texture when the sol concentration
is lower than 0.30M. With the concentration increasing up to 0.30M, the columnar-grained structures can not be obtained.
Among all the PST thin films, the thin film derived with 0.25M sol has better dielectric characteristics. The dielectric
constant, dielectric loss, tunability and FOM are 329, 0.011, 58.0% and 52.8, respectively.
Journal of Electroceramics 04/2012; 21(1):664-667. · 1.19 Impact Factor
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ABSTRACT: (1-x)(Bi<sub>0.9</sub>La<sub>0.1</sub>)FeO<sub>3-x</sub>PbTiO<sub>3</sub> (BLF-PT) crystalline solutions for x = 0.35, 0.37, 0.4, 0.43 and 0.45 have been prepared by the solid-state reaction method. The X-ray diffraction analysis shows that BLF-PT has a single perovskite phase with mixed tetragonal and rhombohedral phases between x = 0.4 and 0.43. The Curie temperature of BLF-PT for x = 0.4 attains 460degC, which is about 80degC higher than that of hard Pb(Zr,Ti)O<sub>3</sub> ceramics. The remnant polarization and piezoelectric constant of BLF-PT for x = 0.4 reach 38 muC/cm<sup>2</sup> and 112 pC/N, respectively. The planar coupling factor k<sub>p</sub> of BLF-PT for x = 0.4 remains stable at temperature increases of up to 360degC. The impedance spectroscopy study reveals that the high temperature conduction of BLF-PT may be attributed to the motion of oxygen vacancies within the material. Our results indicate that BLF-PT is a promising candidate for high temperature applications.
IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 10/2009; · 1.69 Impact Factor
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ABSTRACT: Crystalline solutions of 0.65 (Bi<sub>0.94</sub>La<sub>0.06</sub>) (Ga<sub>x</sub>Fe<sub>1-x</sub>)O<sub>3</sub>-0.35PbTiO<sub>3</sub> ceramics (BLGF-PT) for x = 0 and 0.05 have been fabricated by the solid-state reaction method. X-ray diffraction (XRD) was utilized to characterize the crystal structure and examine any possible impurities existing in the ceramics. The effects of Ga substitution on dielectric properties of the samples were studied at frequencies from 10<sup>2</sup> to 10<sup>6</sup> Hz over a temperature range from 20 to 620degC. The results indicate that Ga modification can reduce the room temperature dielectric loss. The conduction mechanism of the material was investigated using ac conductivity. It is concluded that electrons originating from Fe<sup>2+</sup> and oxygen ion vacancies are the main charge carriers, and Ga doping could decrease the electronic conduction effectively. The frequency dependence of ac conductivity was found to follow Jonscher's universal power law.
IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 10/2009; · 1.69 Impact Factor
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ABSTRACT: Bismuth ferrite and lead titanate composite multiferroic films (xBiFeO<sub>3</sub>-(1-x)PbTiO<sub>3</sub>, BFO-PT films) were deposited on Pt/Ti/SiO<sub>2</sub>/Si substrates by sol-gel method. In this report, the value of x varies from 0.5 to 0.8. The composition dependence (dependence of x) of BFO-PT films is studied. X-ray diffraction analysis reveals that all films are well crystallized in tetragonal phase. It discovers that enhanced ferroelectricity and decreased coercive field can be obtained by reducing the content of BFO (decreasing x). Film for x=0.7 shows the optimized properties, with a very low leakage density about 3.3 times 10<sup>-7</sup> A/cm<sup>2</sup> at 100 kV/cm, maintaining the values of remanent polarization of 35.5 muC/cm<sup>2</sup> and coercive field of 165 kV/cm at 680 kv/cm at room temperature.
Applications of Ferroelectrics, 2009. ISAF 2009. 18th IEEE International Symposium on the; 09/2009
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ABSTRACT: BiFeO<sub>3</sub>-PbTiO<sub>3</sub> (BFO-PT) thin films were fabricated by sol-gel technology. X-ray diffraction pattern reveals the BFO-PT films are in rhombohedral perovskite phase with random orientations. By Pt/BFO-PT/ITO/glass capacitor structure, co-measurement of electrical and optical responses can be achieved. Remanent polarization of 2Pr~40 muC.cm<sup>-2</sup> and leakage current density of 2.5times10<sup>-5</sup> A/cm<sup>2</sup> at 100 kV/cm are obtained in BFO-PT/ITO/glass, which are comparable to those in BFO-PT film on Pt/Si. The absorption spectrum shows that the light with wavelength less than 500 nm can be absorbed by BFO-PT/ITO/glass, which makes the film presenting in orange-yellow color. The optical band gap of BFO-PT thin film is analyzed and derived to be about 2.9 eV for direct band gap and 2.3 eV for indirect band gap. It indicates that not only ultraviolet but also visible light may affect the motion of electrons/carriers in BFO-PT films. With this idea, BFP-PT film may be expected in integration in optic-electronics with solar source.
Applications of Ferroelectrics, 2009. ISAF 2009. 18th IEEE International Symposium on the; 09/2009
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ABSTRACT: Crystalline solutions of 0.65 Bi(0.94)La(0.06)) (Ga(x)Fe(1-x))O(3)-0.35PbTiO(3) Ceramics (BLGF-PT) for x = 0 and 0.05 have been fabricated by the solid-state reaction method. X-ray diffraction (XRD) was utilized to characterize the crystal structure and examine any possible impurities existing in the ceramics. The effects of Ga substitution on dielectric properties of the samples were studied at frequencies from 10(2) to 10(6) Hz over a temperature range from 20 to 620 degrees C. The results indicate that Ga modification can reduce the room temperature dielectric loss. The conduction mechanism of the material was investigated using ac conductivity. It is concluded that electrons originating from Fe(2+) and oxygen ion vacancies are the main charge carriers, and Ga doping could decrease the electronic conduction effectively. The frequency dependence of ac conductivity was found to follow Jonscher's universal power law.
IEEE transactions on ultrasonics, ferroelectrics, and frequency control 09/2009; 56(9):1826-30. · 1.80 Impact Factor
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ABSTRACT: The use of ferroelectric ceramics in microwave devices requires that they possess low-loss, frequency-stable and highly tunable properties. The problems of traditional barium strontium calcium titanate ceramics are higher loss and inappropriate work temperature dependence. In this work, a conventional mixed oxide route was used to prepare BaTiO3, SrTiO3 and CaTiO3 precursor powders. The BaTiO3, SrTiO3 and CaTiO3 powders were thoroughly ball mill mixed. They were then added to 5 wt% polyvinyl alcohol and pressed under a uni-axial pressure of 220 MPa into discs of 12 mm diameter. We introduced nano-grains of barium strontium titanate (BST) into the BSCT ceramic by nano-grain pervasion techniques to fabricate compositionally nonuniform BSCT ceramic samples. The nano-particles of BST are prepared with the sol–gel method. The sol–gel was subjected to ultrasonic irradiation and then vacuum methods in order to easily introduce nanoparticles into bulky BSCT. The ceramics do not show a sharp change in the dielectric constant and have a wide range of Curie temperature distribution. This is attributed to the presence of a compositionally nonuniform micro-area in the samples. Compared with uniform-composition BSCT, compositionally nonuniform BSCT has favourable dielectric properties. These results suggest that the compositionally nonuniform BSCT ceramics are promising candidates as tunable microwave elements.
Journal of Physics D Applied Physics 02/2009; 42(6):065403. · 2.54 Impact Factor
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ABSTRACT: Crystalline solutions of 0.57( Bi <sub>1-x</sub> La <sub>x</sub>) FeO <sub>3</sub>-0.43 PbTiO <sub>3</sub> (BLF-PT) for x=0 , 0.1, 0.2, and 0.3 have been fabricated by the solid state reaction method. The dielectric constant of BLF-PT was significantly enhanced by using La substitutions, reaching about 1850 for x=0.3 . The ferroelectric-paraelectric phase transition of BLF-PT becomes more diffused with a decreased transition temperature for higher La concentration. BLF-PT of x=0.2 exhibits multiferroic characteristics with the simultaneously enhanced remnant magnetization and polarization of 0.119 emu/g and 33.5 μ C / cm <sup>2</sup> , respectively.
Journal of Applied Physics 10/2008; · 2.17 Impact Factor
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ABSTRACT: Well-sintered (Na<sub>0.5</sub>K<sub>0.5</sub>)NbO<sub>3-x</sub> mol% V<sub>2</sub>O<sub>5</sub> ceramics (abbreviated as NKN-V) with fine electrical properties were successfully prepared by conventional solid-state reaction through the careful control of processing conditions. The sintering behavior, phase structure, and electrical properties of the V<sub>2</sub>O<sub>5</sub>-doped NKN ceramics were investigated. Results show that when the V<sub>2</sub>O<sub>5</sub> content is 0.6 mol%, the NKN ceramics attained the maximum density of 4.46 g/cm<sup>3</sup> (about 98.9% of the theoretical density) at 1060degC, and therefore possessed enhanced electrical properties. But when the V<sub>2</sub>O<sub>5</sub> content continued increasing, the density decreased. The secondary phase (Na<sub>2</sub>V<sub>6</sub>O<sub>16</sub>) could be detected by XRD analysis in all samples except x = 0 mol%. The Curie temperature of the NKN-based materials was found to decrease with the increase of V<sub>2</sub>O<sub>5</sub>. The dielectric properties of NKN ceramics doped with 0.6 and 0.9 mol% V<sub>2</sub>O<sub>5</sub> were better than that of pure NKN ceramics. In addition, annealing treatment was proved to be an effective technique for improving dielectric properties and reducing the leakage current density.
IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 06/2008; · 1.69 Impact Factor
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ABSTRACT: Fe-doped Ba<sub>0.6</sub>Sr<sub>0.4</sub>TiO<sub>3</sub> (BST) thin films were prepared on Pt/Si substrates by the pulsed-laser deposition method. The concentrations of Fe dopants vary from 0.1 mol% to 1.0 mol%. Our results indicate that a certain amount of Fe dopants can decrease the dielectric loss of BST thin films without causing the significant reduction of the tunability. The leakage current of BST thin films also was reduced by the addition of Fe dopants. BST thin films doped with 0.3 mol% Fe ions show a minimum dielectric loss of 0.88% at 10<sup>6</sup> Hz, which is 1.7% for the undoped BST films. Moreover, the 0.3 mol% Fe-doped BST films reveal a maximum figure of merit (FOM) of 51, indicating the improved comprehensive dielectric and tunable properties.
IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 01/2008; · 1.69 Impact Factor
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ABSTRACT: Crystalline solutions of 0.57(Bi<sub>1-infin</sub>La<sub>infin</sub>)FeO<sub>3</sub>-0.43PbTiO<sub>3</sub> (BLF-PT) for x = 0, 0.1, 0.2, and 0.3 were fabricated by the traditional solid state reaction method. X-ray diffraction analysis revealed that the tetragonal-to-rhombohedral phase transformation of BLF-PT occurred with an increase of the La content. The dielectric and ferroelectric properties of BLF-PT were investigated at room temperature for different La contents. BLF-PT revealed strong ferroelectric characteristics for the lower La composition, and transferred to relaxor ferroelectrics for x > 0.2. The dielectric constant and remanent polarization were 1461 and 33.5 muC/cm<sup>2</sup>, respectively, for BLF-PT of x = 0.2. The dielectric constant and polarization of BLF-PT were enhanced simultaneously with increasing La content. Our results demonstrate that BLF-PT is a competitive piezoelectric ceramic.
IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 01/2008; · 1.69 Impact Factor
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ABSTRACT: Pb<sub>0.3</sub>Sr<sub>0.7</sub>TiO<sub>3</sub>(PST) thin films were deposited on Pt coated Si(100) substrates by sol-gel techniques using different sol-concentrations. The structural and dielectric characteristics of PST thin films as a function of the sol-concentration were investigated. PST thin films reveal a columnar texture through the thickness when the sol-concentration is lower than 0.3 M. PST thin films derived from 0.35 M sol show better dielectric characteristics with the dielectric constant, dielectric loss, tunability and FOM of 206, 0.01009, 47.5% and 47.07, respectively. The temperature dependence of the dielectric constant, dielectric loss and tunability of PST thin films were investigated in the temperature range of -140~120 exhibiting a dielectric peak of around -45 .
Applications of Ferroelectrics, 2007. ISAF 2007. Sixteenth IEEE International Symposium on; 06/2007
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ABSTRACT: Crystalline solutions of 0.57(B<sub>1-x</sub>La<sub>x</sub>)FeO<sub>3</sub>-0.43PbTiO<sub>3</sub> (BLF-PT) for x=0, 0.1, 0.2 and 0.3 have been fabricated by traditional solid state reaction method. X-ray diffraction (XRD) analysis reveals that the tetragonal to rhombohedral phase transformation of BLF-PT occurs with the increase of La content. The dielectric and ferroelectric properties of BLF-PT were investigated at room temperature for different La contents. BLF-PT reveals strong ferroelectric characteristics for the lower La composition, which transfers to the relaxor ferroelectrics for x>0.2. The dielectric constant and remanent polarization achieve of 1461 and 33.5 muC/cm respectively for BLF-PT of x=0.2. The dielectric constant and polarization of BLF-PT are enhanced simultaneously with increasing La content. Our results demonstrate that BLF-PT are competitive piezoelectric ceramics.
Applications of Ferroelectrics, 2007. ISAF 2007. Sixteenth IEEE International Symposium on; 06/2007
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ABSTRACT: BiFeO<sub>3</sub> -PbTiO<sub>3</sub> (BFO-PT) films were synthesized by sol-gel method with the annealing temperatures to be 550degC, 600degC, and 650degC, respectively. The structure and morphology of the films were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The dielectric constant and loss factor are measured. The leakage current density is also performed to check the conductivity of the films. The effect of annealing temperature of the BFO-PT films on the dielectric properties is obvious with the film annealed at 600degC presenting better dielectric behavior.
Applications of Ferroelectrics, 2007. ISAF 2007. Sixteenth IEEE International Symposium on; 06/2007
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ABSTRACT: Ba<sub>0.6</sub>Sr<sub>0.4</sub>Cr<sub>x</sub>Ti<sub>1-x</sub>O<sub>3</sub> (BSCT) films were prepared by pulsed laser deposition with the value of x varying from 0 mol% to 2.0 mol%. X-ray diffraction measurement detected an increasing in lattice parameters which could be due to the characteristic of film growth process. Dielectric properties of the BSCT films were measured. The dissipation factors were decreased in the Cr-doped films. The highest Figure of Merit (FOM) value of 33.3 was obtained in 1.0 mol%-doped BSCT film. As a result, the effect of Cr doping is positive.
Applications of Ferroelectrics, 2007. ISAF 2007. Sixteenth IEEE International Symposium on; 06/2007
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ABSTRACT: Fe-doped Ba<sub>0.6</sub>Sr<sub>0.4</sub>TiO<sub>3</sub> (BST) thin films were prepared on Pt/Si substrates by the pulsed laser deposition method. The concentrations of Fe dopants vary from 0.1 mol% to 1.0 mol%. Our results indicate that a certain amount of Fe dopants can decrease the dielectric loss of BST thin films without causing the significant reduction of the tunability. The leakage current of BST thin films was also reduced by addition of Fe dopants. BST thin films doped with 0.3 mol% Fe ions show a minimum dielectric loss of 0.88 % at 10 Hz, which is 1.7 % for the undoped BST films. Moreover, the 0.3 mol% Fe-doped BST films reveal a maximum figure of merit (FOM) of 51, indicating the improved comprehensive dielectric and tunable properties.
Applications of Ferroelectrics, 2007. ISAF 2007. Sixteenth IEEE International Symposium on; 06/2007
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ABSTRACT: Solid solutions of La and Ba modified (1-x)BiFeO<sub>3</sub>-xPbTiO<sub>3</sub> were prepared by the mixed oxides method. The 10 at% of La<sup>3+</sup> and Ba<sup>2+</sup> substituents were utilized to substitute Bi<sup>3+</sup> and Pb<sup>2+</sup> ions respectively. These cations enter into the crystalline lattice to modify the structure and properties of BiFeO<sub>3</sub>-PbTiO<sub>3</sub>. The morphotropic phase boundary of (1-x)(Bi,La)FeO<sub>3</sub>-x(Pb,Ba)TiO<sub>3</sub> (BLF-PBT) appears at x=0.4 accompanying by the rhombohedral-tetragonal phase transition. It is found that (1-x)BLF-xPBT reveals enhanced ferroelectric and magnetic properties in the vicinity of the MPB. The remnant polarization and magnetization achieve of 26 muC/cm and 0.06 emu/g, respectively. Our results indicated that (1-x)Bi(Fe,Ga)O<sub>3</sub>-xPbTiO<sub>3</sub> is of the insulating and switchable multiferroics.
Applications of Ferroelectrics, 2007. ISAF 2007. Sixteenth IEEE International Symposium on; 06/2007
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ABSTRACT: Ferroelectric Pb(Zr<sub>0.53</sub>Ti<sub>0.47</sub>)O<sub>3</sub> thin films with thickness of around 800 nm were prepared on LaNiO<sub>3</sub> (LNO) buffered SiO<sub>2</sub>/Si substrates by sol-gel method. The LNO buffer layer serves as the bottom electrode and the template for growing PZT thin films with preferred orientation. The (110)-textured PZT thin films can be obtained on 250 nm-thick LNO buffered SiO<sub>2</sub>/Si substrates. Upon using the LNO buffer layer, the annealing temperature of the PZT films is lowered to 600degC. Our results indicate that PZT thin films prepared on LNO buffered Si substrates have good structural and dielectric properties for sensor and actuator applications.
Applications of Ferroelectrics, 2007. ISAF 2007. Sixteenth IEEE International Symposium on; 06/2007
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ABSTRACT: Multiferroic BiFeO<sub>3</sub>-CoFe<sub>2</sub>O<sub>4</sub> (BFO-CFO) double-layer thin film has been deposited on platinized silicon substrate by pulsed-laser deposition. The BFO and CFO thin layers are deposited at 450 and 600 degC respectively. The diffraction peaks from spinel CoFe<sub>2</sub>O<sub>4</sub> phases can be observed from the x-ray diffraction patterns of the double-layer BFO-CFO films. Dielectric constant and loss of the BFO-CFO films are of around 60 and 0.06 respectively, changing little with increasing the frequency. The leakege current density is about 10<sup>-6</sup> A/cm<sup>2</sup> under the field of 100 kV/cm. BFO-CFO thin films exhibit good ferromagnetic properties with the saturation magnetization of 120 emu/cm<sup>3</sup> .
Applications of Ferroelectrics, 2007. ISAF 2007. Sixteenth IEEE International Symposium on; 06/2007
