Peng Qi

China University of Petroleum, Peping, Beijing, China

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Publications (33)45.46 Total impact

  • [show abstract] [hide abstract]
    ABSTRACT: Lead-free alkaline niobate-based piezoceramics, (Na0.52K0.435Li0.045)Nb0.87Sb0.08Ta0.05O3 (abbreviated KNLNT-S8), were prepared by conventional solid-state sintering method. The effects of sintering temperature on microstructure and piezoelectric properties of the (Li, Sb, Ta)-modified (Na, K) NbO3 were investigated. Microstructure of the samples sintered at different temperatures was observed by scanning electron microscopy (SEM) and optical microscopy. The KNLNT-S8 sample sintered at 1100°C possessed highest piezoelectric constant d 33 and high-field piezoelectric strain coefficient d 33 * of 332 pC/N and 530 pm/V, respectively, with electromechanical coupling factors k p of 0.52 and k t of 0.48.
    Physics Research International. 01/2011; 2011.
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    ABSTRACT: The effect of (Sc,Ta,Ce) doping on the properties of Bi <sub>3</sub> TiNbO <sub>9</sub> (BTNO)-based ceramics was investigated. The cerium modification greatly improves the piezoelectric activity of Bi <sub>3</sub>( Ti <sub>0.96</sub> Sc <sub>0.02</sub> Ta <sub>0.02</sub>) NbO <sub>9</sub> -based ceramics and significantly decreases the dielectric dissipation. The d<sub>33</sub> of Bi <sub>3</sub> Ti <sub>0.96</sub> Sc <sub>0.02</sub> Ta <sub>0.02</sub> NbO <sub>9</sub>+x wt  % CeO <sub>2</sub> (x=0.35) was found to be 18 pC/N, the highest value among the BTNO-based ceramics and almost three times as much as the reported d<sub>33</sub> values of the pure BTNO ceramics (∼6 pC / N ) . The modification increased the resistivity ρ of the samples extremely, resolving the low resistivity problem for high temperature applications. The dielectric spectroscopy shows that the T<sub>C</sub> for all the ceramics is higher than 900 °C . The mechanical quality factor Q and planar coupling factors k<sub>p</sub> and k<sub>t</sub> of Bi <sub>3</sub> Ti <sub>0.96</sub> Sc <sub>0.02</sub> Ta <sub>0.02</sub> NbO <sub>9</sub>+0.35 wt  % CeO <sub>2</sub> ceramic were found to be 2835, 9%, and 23%, respectively, and it has high T<sub>C</sub> and stable piezoelectric properties, demonstrating that the (Sc,Ta,Ce) modified BTNO-based material is a- wonderful candidate for high temperature applications.
    Journal of Applied Physics 08/2008; · 2.21 Impact Factor
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    ABSTRACT: The effect of (Li,Ce) substitution at the A-site on the properties of Na0.25K0.25Bi4.5Ti4O15 (NKBT)-based ceramics was investigated. The piezoelectric coefficient d33 of the [(Na0.5K0.5)Bi]0.42(LiCe)0.04[]0.04Bi4Ti4O15 ceramic was found to be 25 pC N−1, the highest value of the NKBT-based ceramics, and almost twice the d33 values of pure NKBT ceramics (∼13 pC N−1). The thickness coupling factor kt was found to be 20%, which, together with the high TC (∼615 °C) and stable piezoelectric properties, suggests that (Li,Ce)-modified NKBT-based materials are promising candidates for high-temperature applications.
    Scripta Materialia. 07/2008; 59(1):115–118.
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    ABSTRACT: Lead-free piezoelectric ceramics (Na0.53K0.422Li0.048) (Nb0.89Sb0.06Ta0.05)O3(NKLNST) + x mol SrCO3 are prepared by conventional solid state sintering method. The specimens with pure perovskite structure show tetragonal phase at x = 0.02. A lattice parameter discontinuity is found in the specimens with 0.004
    Chinese Physics Letters 01/2008; 25(7):2573-2576. · 0.81 Impact Factor
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    ABSTRACT: Lead-free alkaline niobate based (Na0.52K0.48−xLix)Nb1−x−ySbxTayO3 piezoceramics have been prepared by the conventional mixed oxide method without using other techniques. An experimental formula for producing a set of ceramics with high piezoelectric properties is obtained while cutting down the Ta content and maintaining a high Curie temperature. The highest piezoelectric constant d33 is 308 pC/N, with a dielectric loss tan δ of about 2.0% and a Curie temperature of 339 °C. The samples also possess outstanding high-field piezoelectric strain effects. The high-field piezoelectric strain coefficient d33* is as high as 490 pm/V. (Li, Sb, Ta) modified (Na,K)NbO3 shifts the orthorhombic to tetragonal phase transition to near room temperature, which plays an important role in the improvement of the piezoelectric properties.
    Journal of Applied Physics 03/2007; 101(5):054103-054103-4. · 2.21 Impact Factor
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    ABSTRACT: Newly developed sintering aid Na5.6Cu1.2Sb10O29 (NCS) and lead-bismuth-free piezoceramics (Na0.5K0.44Li0.06) Nb0.95Sb0.05O3 (NKLNS) were prepared by the conventional solid state reaction. The effects of sintering aid NCS on the electrical properties of NKLNS were investigated. It was found that the addition of a proper amount of sintering aid NCS to NKLNS is effective not only on improving the density and the piezoelectric activity, but also on reducing the dielectric loss of NKLNS. The NKLNS doped with 0.4 mol% NCS has a piezoelectric constant d 33 as high as 261pC/N and an electromechanical coupling factor k 33 above 60%. These results show that NCS-doped NKLNS is a promising and practicable candidate for lead-bismuth-free piezoceramics.
    Chinese Science Bulletin 01/2007; 52(4):566-569. · 1.32 Impact Factor
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    ABSTRACT: The effect of (LiCe) substitution for A site on the properties of ( Na Bi )<sub>0.48</sub>◻<sub>0.04</sub> Bi <sub>2</sub> Nb <sub>2</sub> O <sub>9</sub> (NB◻N)-based ceramics was investigated. The coercive fields (E<sub>C</sub>) of NB◻N)-based ceramics were significantly decreased from 61.0 to 32.5 kV / cm and the Curie temperature (T<sub>C</sub>) gradually decreases from 820 to 803 ° C with increasing the (LiCe) modification. The piezoelectric coefficient d<sub>33</sub> , planar coupling factor k<sub>p</sub> , and mechanical quality factor Q of ( Na Bi )<sub>0.38</sub>( Li Ce )<sub>0.05</sub>◻<sub>0.14</sub> Bi <sub>2</sub> Nb <sub>2</sub> O <sub>9</sub> ceramic were found to be 27 pC / N , 11.2%, and 2600, respectively, together with the high T<sub>C</sub> (∼809 ° C ) and stable piezoelectric properties, demonstrating that the (LiCe) modified NB◻N-based material a promising candidate for high temperature applications.
    Applied Physics Letters 08/2006; · 3.79 Impact Factor
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    ABSTRACT: Lead-free potassium sodium niobate piezoelectric ceramics substituted with lithium and antimony ( Na <sub>0.5</sub> K <sub>0.5</sub>)<sub>1-x</sub>( Li Sb )<sub>x</sub> Nb <sub>1-x</sub> O <sub>3</sub> have been synthesized by conventional solid state sintering method. Compositionally engineered around the orthorhombic-tetragonal polymorphic phase transition, the dielectric and piezoelectric properties were further enhanced with the addition of lithium and antimony substituted into the perovskite structure. The combined effects of lithium and antimony additions resulted in a downward shift in the orthorhombic-tetragonal (T<sub>O-T</sub>) without significantly reducing T<sub>C</sub> . The dielectric, piezoelectric, and electromechanical properties were found to be ε/ε<sub>0</sub>≫1300 , d<sub>33</sub>≫260 pC / N , and k<sub>p</sub>≫50% , while maintaining low dielectric loss. The enhanced polarizability associated with the polymorphic T<sub>O-T</sub> transition and high T<sub>C</sub> transition (∼390 ° C ) should provide a wide range of temperature operation.
    Applied Physics Letters 06/2006; · 3.79 Impact Factor
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    ABSTRACT: The effects of Dy2O3 on the microstructure and electrical properties of the SnO2 based varistor system were investigated. It was found that Dy2O3 significantly affects the grain size and electrical properties of the SnO2-based varistors. The sample with 1.00 mol% Dy2O3 has the best nonlinear electrical property and the highest nonlinear coefficient (α = 26.3) among all samples. By SEM, TEM and EDS images, it was found dysprosium segregates at the grain boundary, which is responsible for “p-type characteristics” of the grain boundaries. The reason that grain size decreases with increasing Dy2O3 concentration is given. The reason why the varistor sample has the excellent nonlinearity is explained.
    Materials Science and Engineering: B. 01/2006;
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    ABSTRACT: Without Abstract
    Journal of Materials Science 01/2006; 41(4):1273-1275. · 2.16 Impact Factor
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    ABSTRACT: The microstructure development of SnO2·CuO based ceramic material was analyzed by XRD and SEM and the electrical properties were investigated by J-E relation. The secondary phases of copper oxide were found by the XRD. Copper oxide could make tin oxide densify and advance the grain growth, while tantalum oxide would retard the grain growth. Excess copper would centralize at the grain boundaries and prevent the mass transport. The high nonlinear coefficient (α = 27.3) and low leakage current density (JL = 16 μA cm−2) for the 0.05 mol% Ta2O5-doped SnO2·CuO based varistor sample were obtained. The modified defect barrier model for CuO and Ta2O5-doped SnO2 based varistors was introduced.
    Journal of Materials Science 11/2005; 40(24):6459-6462. · 2.16 Impact Factor
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    ABSTRACT: The effects of various donors such as Nb, Sb, Ta, and V on the densification and nonlinear current-density J –electrical-field E relations of tin oxide ceramics are investigated. The room-temperature resistivity ρ and the three vital varistor parameters, the nonlinear coefficient α , breakdown electrical field E<sub>B</sub> , and leakage current density J<sub>L</sub> , are studied as a function of donor concentration. Minor donors make highly resistive Sn O <sub>2</sub>∙ Cu O ceramics nonlinear or conductive. The optimum doping samples with tantalum or niobium show promising properties for high-voltage varistor application.
    Journal of Applied Physics 07/2005; · 2.21 Impact Factor
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    ABSTRACT: The effect on microstructure and electrical properties of (Co,Nb)-doped SnO2 varistors upon the addition of Yb2O3 was investigated by scanning electron microscopy and by determining J–E (current density vs. electric field), ɛ–f (relative permittivity vs. frequency) and Z′′–Z′ (reactance vs. resistance) relations. The threshold electric field of the SnO2-based varistors increased significantly from 412 V/mm to 1430 V/mm, and the relative dielectric constants of the SnO2-based varistors decreased greatly from 1571 to 230 as Yb2O3 concentration was increased up to 0.98 mol%. The significant decrease of the SnO2 grain size, from 13.68 μm to 6.88 μm with increasing Yb2O3 concentration over the range of 0–0.98 mol%, is the origin for the increase in the threshold voltage and decrease of the dielectric constants. The grain size reduction is attributed to the segregation of Yb2O3 at grain boundaries hindering the SnO2 grains from conglomerating into large particles. Varistors were found to have superhigh threshold voltage and comparatively large nonlinear coefficient α. For 0.05 mol% Yb2O3-doped sample, threshold electric field EB and nonlinear coefficient α were measured to be 593 V/mm and 42.4, and for 0.98 mol% Yb2O3-doped sample, EB and α were 1430 V/mm and 37, respectively. Superhigh threshold voltage and large nonlinear coefficient α qualify the Yb-doped SnO2 varistor as an excellent candidate for high voltage protection system.
    Materials Science and Engineering: B. 05/2005; 119(1):94–98.
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    ABSTRACT: The effects of In2O3 doping and sintering temperature on the microstructure and electrical properties of (Co,Ta)-doped SnO2 varistors were investigated and the maximal non-linear co-efficient of α = 51 of the sample doped with 0.08 mol% In2O3 sintered at 1350 °C was obtained. It was found that the breakdown electrical field and resistivity of grain boundaries increased significantly with increasing In2O3 concentration or decreasing sintering temperature. The sample doped with 0.12 mol% In2O3 sintered at 1350 °C has the highest breakdown electrical field of 2592 V/mm. The relative dielectric constant decreased with increasing In2O3 concentration or decreasing sintering temperature. The decrease or increase of breakdown electrical field, increase or decrease of relative dielectric constant with altering In2O3 concentration and sintering temperature is mainly attributed to the increase or decrease of the grain size. The mechanism of the variation of SnO2 grain size was discussed.
    Journal of Non-Crystalline Solids 04/2005; 351(s 10–11):941–945. · 1.60 Impact Factor
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    ABSTRACT: The effect of Co2O3 on the microstructure and electrical properties of Ta-doped SnO2 varistors was investigated. It was found that a sample doped with 0.1 mol% Co2O3 had the highest nonlinear coefficient α = 33, the highest breakdown electrical field EB = 872 V mm−1 and the lowest relative dielectrical constant εr = 598 (measured at 1 kHz). However, 0.1 mol% Co2O3 is not sufficient for densification of SnO2 ceramics, and the relative density of the sample doped with 0.1 mol% Co2O3 (85.8%) is much lower than that of the samples doped with 0.3, 0.5, 0.8 and 1.2 mol% Co2O3 (about 98%). The highest breakdown electrical field and lowest relative dielectric constant of the sample doped with 0.1 mol% Co2O3 are mainly the result of the loose microstructure and the smallest average grain size. The measurements of grain boundary barrier height, ΦB, and grain boundary resistance, RGB, indicate that CoSn× should be located at the depletion layer and is important to the formation of the grain boundary barrier.
    Journal of Physics D Applied Physics 03/2005; 38(7):1072. · 2.53 Impact Factor
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    ABSTRACT: The CuO and Ta2O5-doped SnO2 system was obtained by conventional ceramics processing. The ceramic phases of samples was analyzed by X-ray diffraction (XRD) and the microstructure by means of scanning electron microscopy (SEM). The electrical field of a single phase of CuO and Ta2O5-doped SnO2 system was studied as a function of current density behavior and compared with the CoO and Ta2O5-doped SnO2 system. A high nonlinear coefficient α=37.9 was obtained. To illustrate the grain–boundary barrier formation of CuO and Ta2O5-doped SnO2-based varistors, a modified defect barrier model is introduced.
    Materials Letters. 02/2005; 59(s 2–3):201–204.
  • Key Engineering Materials - KEY ENG MAT. 01/2005;
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    ABSTRACT: The effect on the microstructure and electrical properties of (Co, Ta)-doped SnO2 varistors upon the addition of Gd2O3 was investigated. The threshold electric field of the SnO2 based varistors increased significantly from 720 V/mm to 1455 V/mm, the relative dielectric constants of the SnO2 based varistors decreased greatly from 833 to 330 as Gd2O3 concentration was increased up to 1.2 mol%. The significant decrease of the SnO2 mean grain size, from 3.8 to 1.6 µ m with increasing Gd2O3 concentration over the range of 0 to 1.2 mol%, is the origin for increase in the threshold voltage and decrease of the dielectric constants. The mean grain size reduction is attributed to the segregation of Gd2O3 at grain boundaries hindering the SnO2 grains from conglomerating into large particles. Varistors were found to have superhigh threshold voltage and comparatively large nonlinear coefficient a . For 0.8 mol% Gd2O3-doped sample, threshold electrical field E and nonlinear coefficient a were measured to be 1125 V/mm and 24.0, for 1.2 mol% Gd2O3-doped sample, E and a were 1355 V/mm and 23.0. Superhigh threshold voltage and large nonlinear coefficient qualify the Gd-doped SnO2 varistor as an excellent candidate in use for high voltage protection system.
    Journal of Electroceramics 01/2005; 14(2):133-137. · 1.14 Impact Factor
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    ABSTRACT: The effects of CuO on the SnO2·Co2O3·Ta2O5 varistor system sintered at 1250°C for 80min were investigated. It was found that CuO significantly affects the grain size and electrical properties of the SnO2-based varistors. The grain size rises from 4.7 to 11.4μm, the breakdown electrical field decreases from 485 to 265Vmm−1 and relative dielectric constant (at 1kHz) increases from 970 to 2451 with an increase in CuO concentration from 0.00 to 1.00mol%. The sample with 0.25mol% CuO has the best nonlinear electrical property and the highest nonlinear coefficient (α=15.7) among all samples. The reason why grain size increases with increasing CuO concentration is explained. Also, the interpretation of the increase in nonlinearity is given.
    Materials Science and Engineering B-advanced Functional Solid-state Materials. 01/2005; 116(1):54-58.
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    ABSTRACT: The varistor properties of Sc2O3-doped SnO2·Co2O3·Nb2O5 ceramics were investigated. It was found that the non-linear coefficient presents a peak of 17.1 at the concentration of 0.06mol% Sc2O3, the average grain size decreases from 10 to 5μm, the breakdown electrical field increases from 199 to 1790V/mm and relative electrical permittivity decreases from 2600 to 60 as Sc2O3 concentration was increased up to 0.09mol%. The increase of the breakdown electrical field with increasing Sc2O3 concentration is mainly attributed to the decrease of the average grain size. The reason why the permittivity decreases with increasing Sc2O3 concentration was originated from the ratio of the grain size to the barrier width. To illustrate the grain-boundary barrier formation of (Sc, Co, Nb)-doped SnO2 varistors, a modified defect barrier model was introduced, in which the negatively charged acceptors substituting for Sn ions should be located at SnO2 lattice sites in the depletion layers, instead at the grain interfaces.
    Ceramics International - CERAM INT. 01/2005; 31(2):287-291.

Publication Stats

54 Citations
45.46 Total Impact Points

Institutions

  • 2011
    • China University of Petroleum
      Peping, Beijing, China
  • 2003–2008
    • Shandong University
      • • School of Physics and Microelectronics
      • • State Key Laboratory for Crystal Materials
      Chi-nan-shih, Shandong Sheng, China