Optically transparent alumina ceramics were fabricated by conventional process and sintered without pressure in H2 atmosphere. The results indicate that relative densities of alumina specimens increase to theoretical ...Optically transparent alumina ceramics were fabricated by conventional process and sintered without pressure in H2 atmosphere. The results indicate that relative densities of alumina specimens increase to theoretical densities （T. D. ） with increasing content of La2O3. With increasing holding time during sintering, much less pores and larger grains were found in the sintered alumina samples. Higher transmittance was achieved in alumina codoped with MgO and La2O3 as compared with that doped with MgO only. The total-transmittance of alumina sample is up to 86% at twavelength range of 300 - 800 nm.展开更多
In recent decades, many additives with different characteristics have been applied to strengthen and toughen Al2O3-based ceramic cutting tool materials. Among them, SiC whiskers and SiC nanoparticles showed excellent ...In recent decades, many additives with different characteristics have been applied to strengthen and toughen Al2O3-based ceramic cutting tool materials. Among them, SiC whiskers and SiC nanoparticles showed excellent performance in improving the material properties. While no attempts have been made to add SiC whiskers and SiC nanoparticles together into the ceramic matrix and the synergistically toughening effects of them have not been studied. An Al2O3-SiCw-SiC np advanced ceramic cutting tool material is fabricated by adding both one-dimensional SiC whiskers and zero-dimensional SiC nanoparticles into the Al2O3 matrix with an effective dispersing and mixing process. The composites with 25 vol% SiC whiskers and 25 vol% SiC nanoparticles alone are also investegated for comparison purposes. Results show that the Al2O3-SiCw-SiCnp composite with both 20 vo1% SiC whiskers and 5 vol% SiC nanoparticles additives have much improved mechanical properties. The flexural strength of Al2O3-SiCw-SiCnp is 730＋ 95 MPa and fracture toughness is 5.6 ± 0.6 MPa.m1/2. The toughening and strengthening mechanisms of SiC whiskers and nanoparticles are studied when they are added either individually or in combination. It is indicated that when SiC whiskers and nanoparticles are added together, the grains are further refined and homogenized, so that the microstructure and fracture mode ratio is modified. The SiC nanoparticles are found helpful to enhance the toughening effects of the SiC whiskers. The proposed research helps to enrich the types of ceramic cutting tool and is benefit to expand the application range of ceramic cutting tool.展开更多
ZrO2-Y2O3 ceramic coating was produced by plasma electrolytic oxidation （PEO） on ZAlSil2Cu3Ni2 alloy. The microstructure and phase composition of the coating were investigated by SEM and XRD.： The results show that...ZrO2-Y2O3 ceramic coating was produced by plasma electrolytic oxidation （PEO） on ZAlSil2Cu3Ni2 alloy. The microstructure and phase composition of the coating were investigated by SEM and XRD.： The results show that adding an appropriate amount of yttrium ion can improve the growing rate of ceramic coating at different oxidation stages and decrease arc voltage. The thickness of ZrO2-Y2O3 coating is 16 μn thicker than that of ZrO2 coating and the maximum oxidation rate improves by 0.6 μm/min. In addition, the arc voltage decreases from 227 to 172 V. It can be seen that the rate of oxidation firstly increases to some extent and then decreases with the content of yttrium ion increasing. The growth rate reaches the maximum while the content of yttrium ion is 0.05 g-L-1The maximum thickness is 90 μm.Compared to ZrO2 coating, the micropores of ZrO2-Y2O3 coating are less and the ceramic layer is repeatedly deposited by ZrO2 and Y2O3 ceramic particles. Meanwhile, the binding force between coating and substrate is better and the coating is uniform and compact. The ceramic layer is mainly composed of c-Y0.15Zr0.85O1.93□0.07, m-ZrO2, α-Al2O3, ,γ-Al2O3 and Y2O3. It is indicated that ZrO2 has beert fully stabilized by yttrium ion through the formation of solid solution.展开更多
The Al2O3-ZrO2（3Y）-SiC composite ceramics used in solar thermal power were prepared by micrometric Al2O3,nano-ZrO2 and SiC powders under the condition of pressureless sintering.The bulk density and bending strength ...The Al2O3-ZrO2（3Y）-SiC composite ceramics used in solar thermal power were prepared by micrometric Al2O3,nano-ZrO2 and SiC powders under the condition of pressureless sintering.The bulk density and bending strength of samples with 10vol% nano-ZrO2 sintered at 1480℃ were 3.222 g/cm3 and 160.4MPa,respectively.The bending strength of samples after 7 times thermal shock tests （quenching from 1000℃ to 25℃ in air medium） is 132.0MPa,loss rate of bending strength is only 17%.The effect of nano-ZrO2 content on the microstructure and performance of Al2O3-ZrO2（3Y）-SiC composite ceramic was investigated.The experimental results show that the bending strength of samples with above 10vol% nano-ZrO2 content has decreased,because the volume expansion resulting from t-ZrO2 to m-ZrO2 phase transformation is excessive;Adding proper nano-ZrO2 would be contributed to improve the thermal shock resistance of the composite ceramics.The Al2O3-ZrO2（3Y）-SiC composite ceramic has promising potential application in solar thermal power.展开更多
Al2O3-13%TiO2 （mass fraction） coatings, prepared by laser cladding on nickel-based alloy, were heated using high frequency induction sources. The coating microstructure and the interface between bond coating and cer...Al2O3-13%TiO2 （mass fraction） coatings, prepared by laser cladding on nickel-based alloy, were heated using high frequency induction sources. The coating microstructure and the interface between bond coating and ceramic coating were characterized by SEM, XRD and EDS. The results show that two-layer substructure exists in the ceramic coating： one layer evolving from fully melted region where the sintered grains grow fully; another layer resembling the liquid-phase-sintered structure consisting of three-dimensional net where the melted Al2O3 particles are embedded in the TiO2-rich matrix. The mechanism of the two-layer substructure formation is also explained in terms of the melting and flattening behavior of the powders during laser cladding processing. The spinel compounds NiAl2O4 and acicular compounds Cr2O3 are discovered in the interface between bond coating and ceramic coating. It proves that the chemical reactions in the laser cladding process will significantly enhance the coating adhesion.展开更多
The dielectric properties and phase transition characteristics of La2O3- and Sb2O3-doped barium strontium titanate ceramics prepared by solid state route were investigated. The microstructure was identified by X-ray d...The dielectric properties and phase transition characteristics of La2O3- and Sb2O3-doped barium strontium titanate ceramics prepared by solid state route were investigated. The microstructure was identified by X-ray diffraction method and scanning electron microscope was also employed to observe the surface morphologies. It is found that （La,Sb）-codoped barium strontium titanate ceramics exhibit typical perovskite structure and the average grain size decreases dramatically with increasing the content of Sb2O3. Both La3＋ ions and Sb3＋ ions occupy the A-sites in perovskite lattice. The dielectric constant and dielectric loss of barium strontium titanate based ceramics are obviously influenced by La2O3 as well as Sb2O3 addition content. The tetragonal-cubic phase transition of La2O3 modified barium strontium titanate ceramics is of second order and the Curie temperature shifts to lower value with increasing the La2O3 doping content. The phase transition of （La,Sb）-codoped barium strontium titanate ceramics diffuses and the deviation from Curie-Weiss law becomes more obvious with the increase in Sb2O3 concentration. The temperature corresponding to the dielectric constant maximum of （La,Sb）-codoped barium strontium titanate ceramics decreases with increasing the Sb2O3 content, which is attributed to the replacement of host ions by the Sb3＋ ions.展开更多
The hip joint femoral head prosthesis was prepared using the Al2O3 material, which was synthesized by high purity alumina micro-powder and Mg- Zr- Y composite addhitives , the cold manufacturing techniques of lathe t...The hip joint femoral head prosthesis was prepared using the Al2O3 material, which was synthesized by high purity alumina micro-powder and Mg- Zr- Y composite addhitives , the cold manufacturing techniques of lathe turning, grade polishing and the matching size correction of the sintered femoral head were studied. The results showed, after being pressed under 200 MPa cold isostatic pressure and being pre-sintered at 1150℃ , the biscuit＇ s strength can meet the demands of lathe turning ; After being grade polished by SiC micro-powder and diamond abrading agent and being size corrected by special instrument, the femoral head prosthesis of Al2O3 ceramic has good surface degree of finish and articulates tightly with femoral handle.展开更多
Fe-Al intermetallic/TiC-Al2O3 ceramic composites were successfully prepared by selfpropagating high-temperature synthesis （SHS） from natural ilmenite, aluminium and carbon as the raw materials. The effects of carbon...Fe-Al intermetallic/TiC-Al2O3 ceramic composites were successfully prepared by selfpropagating high-temperature synthesis （SHS） from natural ilmenite, aluminium and carbon as the raw materials. The effects of carbon sources, preheating time and heat treatment temperature on synthesis process and products were investigated in detail, and the reaction process of the FeTiO3-Al-C system was also discussed. It is shown that the temperature and velocity of the combustion wave are higher when graphite is used as the carbon source, which can reflect the effect of the carbon source structure on the combustion synthesis; Prolonging the preheating time or heat treatment temperature is beneficial to the formation of the ordered intermetallics; The temperature and velocity of the combustion wave are improved, but the disordered alloys are difficult to eliminate with the preheating time prolonged. The compound powders mainly containing ordered Fe3Al intermetallic can be prepared through heat treatment at 750 ℃.展开更多
The main Iimitation to the toughening of the α-Al2O3/Ni composite is the poor bonding atthe interface. which causes the nickel particles to be pulled-out during crack propagation with-out obvious plastic deformation....The main Iimitation to the toughening of the α-Al2O3/Ni composite is the poor bonding atthe interface. which causes the nickel particles to be pulled-out during crack propagation with-out obvious plastic deformation. A proper control of oxygen content at the Al2O3-Ni interfacecan promote wetting at the intedece, and produce a mechanically interlocked and chemically strengthened intedece, causing most of the nickel particles to be stretched to failure and to expe-rience severe plastic deformation during crack propagation in the composite. Fracture toughnesstesting using a modified double cantilever beam method with in situ observation of crack prop-agation in a scanning electron microscope shows that the composite with the strengthenedinterface has a more desirable R-curve behaviour and a higher fracture toughness value than thenormal composite.展开更多
The influences of the PbO-B2O3-CuV2O6 （PBC） additives on the microwave dielectric properties of （Pb0.5Ca0.5） （Fe0.5Nb0.5）O3 （PCFN） ceramics were investigated as a function of sintering temperature from 950 ℃ ...The influences of the PbO-B2O3-CuV2O6 （PBC） additives on the microwave dielectric properties of （Pb0.5Ca0.5） （Fe0.5Nb0.5）O3 （PCFN） ceramics were investigated as a function of sintering temperature from 950 ℃ to 1 100 ℃. The sintering temperature of the specimens with the glass could be lowered from 1125 ℃ to 1 025℃ without the degradation of microwave dielectric properties. The microwave results showed that the dielectric constant cr was not significantly different while Qf values decreased with the increase of CuV206 content of PBC glass. For the specimens doped with PB-CV0.1 glass （81% PbO-9% B203-10% CuV2O6） and sintered at 1 025 ℃ for 3 h, the microwave dielectric properties of Qf=4 823 GHz, Cr=107.1 with TCF=＋15.03 ×10^-6/℃ were obtained.展开更多
The 0.8Pb(Zr0.48Ti0.52)O3 – 0.125Pb(Zn1/3Nb2/3)O3 – 0.075Pb(Mn1/3Nb2/3)O3 + x wt% Fe2O3 ceramics (PZT-PZN-PMnN), where x = 0 ÷?0.35, has been prepared by two-stage calcination method. The effect of Fe2O3 conten...The 0.8Pb(Zr0.48Ti0.52)O3 – 0.125Pb(Zn1/3Nb2/3)O3 – 0.075Pb(Mn1/3Nb2/3)O3 + x wt% Fe2O3 ceramics (PZT-PZN-PMnN), where x = 0 ÷?0.35, has been prepared by two-stage calcination method. The effect of Fe2O3 content on the crystal structure and electrical properties of ceramics has been investigated. The results of X-ray diffraction (XRD) show that all samples have pure perovskite phase with tetragonal structure, the c/a ratio increases with increasing Fe2O3 content. At x = 0.25, electrical properties of ceramics are best: the density (r) of 7.86 g/cm3, the electromechanical coupling factor (kp) of 0.64, the dielectric constant (εr) of 1400, the dielectric loss (tand) of 0.003, the mechanical quality factor (Qm) of 1450, the piezoelectric constant (d31) of 155 pC/N, and the remanent polarization (Pr) of 37 μC/cm2, which makes it as a promising material for high power piezoelectric devices.展开更多
We fabricated YBa2Cu3O7–d bulk ceramics with a domestic microwave oven and investigated the effect of pressure at the press procedure. If the pressure was not high enough, the ratio of BaCuO2 phase became large, esti...We fabricated YBa2Cu3O7–d bulk ceramics with a domestic microwave oven and investigated the effect of pressure at the press procedure. If the pressure was not high enough, the ratio of BaCuO2 phase became large, estimated from x-ray diffraction (XRD) measurements. We found that the pressure should be 700 kgf/cm2 at least in order to suppress the BaCuO2 phase.展开更多
The sintering temperature of Li2ZnTi3O8 ceramics is still high for LTCC-based applications. In this work, V2O5 was doped as the sintering aid. The sintered density, phase composition, grain size, as well as microwave ...The sintering temperature of Li2ZnTi3O8 ceramics is still high for LTCC-based applications. In this work, V2O5 was doped as the sintering aid. The sintered density, phase composition, grain size, as well as microwave dielectric properties of Li2ZnTi3O8 ceramics with the addition of V2O5 were investigated. Based on our research, V2O5 doping effectively promoted the densification of Li2ZnTi3O8 ceramics at about 900°C, without affecting the main crystal phase of the ceramics. Li2ZnTi3O8 ceramics with 0.5 wt% V2O5 doping (sintered at 900°C) exhibited the best microwave dielectric properties (Qf =?22,400 GHz at about 6 GHz, εr = 25.5, and τf = -10.8 ppm/°C). The V2O5-doped Li2ZnTi3O8 ceramics were well cofired with Ag inner paste without cracks and diffusion, indicating its significant potential for LTCC applications.展开更多
Polycrystalline 3Y-TZP/Al2O3 tetragonal zirconia fiber was obtained by the pyrolysis of gel fibers using zirconium oxychloride octahydrate（ZOC） as the raw material. The spinnable zirconia sol was prepared by electro...Polycrystalline 3Y-TZP/Al2O3 tetragonal zirconia fiber was obtained by the pyrolysis of gel fibers using zirconium oxychloride octahydrate（ZOC） as the raw material. The spinnable zirconia sol was prepared by electrolyzing the zirco-nium oxychloride octahydrate（ZOC） solution in the presence of acetic acid and sugar（ sucrose, glucrose or fructose） , in which the molar ratios of CH3 COOH/ZOC and sugar/ZOC were 1.0-4.0 and 0.2-0.4, respectively. The pre- pared tetragonal zireonia fibers sintered at different temperatures showed smooth and crack-free surfaces with diame, ters of 5-10 μm. The addition of Al2O3 enhanced the sintering process and prevented the crystals from growing. Thermogravimetric analysis（TG）, X-ray diffraction （ XRD ）, Fourier transform infrared spectroscopy（FTIR）, and scanning electron microscope（SEM） techniques were used to characterize the prepared fibers.展开更多
文摘Optically transparent alumina ceramics were fabricated by conventional process and sintered without pressure in H2 atmosphere. The results indicate that relative densities of alumina specimens increase to theoretical densities （T. D. ） with increasing content of La2O3. With increasing holding time during sintering, much less pores and larger grains were found in the sintered alumina samples. Higher transmittance was achieved in alumina codoped with MgO and La2O3 as compared with that doped with MgO only. The total-transmittance of alumina sample is up to 86% at twavelength range of 300 - 800 nm.
基金Supported by National Natural Science Foundation of China(Grant No.51175305)
文摘In recent decades, many additives with different characteristics have been applied to strengthen and toughen Al2O3-based ceramic cutting tool materials. Among them, SiC whiskers and SiC nanoparticles showed excellent performance in improving the material properties. While no attempts have been made to add SiC whiskers and SiC nanoparticles together into the ceramic matrix and the synergistically toughening effects of them have not been studied. An Al2O3-SiCw-SiC np advanced ceramic cutting tool material is fabricated by adding both one-dimensional SiC whiskers and zero-dimensional SiC nanoparticles into the Al2O3 matrix with an effective dispersing and mixing process. The composites with 25 vol% SiC whiskers and 25 vol% SiC nanoparticles alone are also investegated for comparison purposes. Results show that the Al2O3-SiCw-SiCnp composite with both 20 vo1% SiC whiskers and 5 vol% SiC nanoparticles additives have much improved mechanical properties. The flexural strength of Al2O3-SiCw-SiCnp is 730＋ 95 MPa and fracture toughness is 5.6 ± 0.6 MPa.m1/2. The toughening and strengthening mechanisms of SiC whiskers and nanoparticles are studied when they are added either individually or in combination. It is indicated that when SiC whiskers and nanoparticles are added together, the grains are further refined and homogenized, so that the microstructure and fracture mode ratio is modified. The SiC nanoparticles are found helpful to enhance the toughening effects of the SiC whiskers. The proposed research helps to enrich the types of ceramic cutting tool and is benefit to expand the application range of ceramic cutting tool.
基金Funded by the National Natural Science Foundation of China(No.51401155)the School Foundation(No.XAGDXJJ1012)The Open Fund of Shaanxi Key Laboratory of Photoelectric Functional Materials and Devices(No.ZSKJ201416)
文摘ZrO2-Y2O3 ceramic coating was produced by plasma electrolytic oxidation （PEO） on ZAlSil2Cu3Ni2 alloy. The microstructure and phase composition of the coating were investigated by SEM and XRD.： The results show that adding an appropriate amount of yttrium ion can improve the growing rate of ceramic coating at different oxidation stages and decrease arc voltage. The thickness of ZrO2-Y2O3 coating is 16 μn thicker than that of ZrO2 coating and the maximum oxidation rate improves by 0.6 μm/min. In addition, the arc voltage decreases from 227 to 172 V. It can be seen that the rate of oxidation firstly increases to some extent and then decreases with the content of yttrium ion increasing. The growth rate reaches the maximum while the content of yttrium ion is 0.05 g-L-1The maximum thickness is 90 μm.Compared to ZrO2 coating, the micropores of ZrO2-Y2O3 coating are less and the ceramic layer is repeatedly deposited by ZrO2 and Y2O3 ceramic particles. Meanwhile, the binding force between coating and substrate is better and the coating is uniform and compact. The ceramic layer is mainly composed of c-Y0.15Zr0.85O1.93□0.07, m-ZrO2, α-Al2O3, ,γ-Al2O3 and Y2O3. It is indicated that ZrO2 has beert fully stabilized by yttrium ion through the formation of solid solution.
文摘The Al2O3-ZrO2（3Y）-SiC composite ceramics used in solar thermal power were prepared by micrometric Al2O3,nano-ZrO2 and SiC powders under the condition of pressureless sintering.The bulk density and bending strength of samples with 10vol% nano-ZrO2 sintered at 1480℃ were 3.222 g/cm3 and 160.4MPa,respectively.The bending strength of samples after 7 times thermal shock tests （quenching from 1000℃ to 25℃ in air medium） is 132.0MPa,loss rate of bending strength is only 17%.The effect of nano-ZrO2 content on the microstructure and performance of Al2O3-ZrO2（3Y）-SiC composite ceramic was investigated.The experimental results show that the bending strength of samples with above 10vol% nano-ZrO2 content has decreased,because the volume expansion resulting from t-ZrO2 to m-ZrO2 phase transformation is excessive;Adding proper nano-ZrO2 would be contributed to improve the thermal shock resistance of the composite ceramics.The Al2O3-ZrO2（3Y）-SiC composite ceramic has promising potential application in solar thermal power.
基金Project (59975046) supported by the National Natural Science Foundation of China
文摘Al2O3-13%TiO2 （mass fraction） coatings, prepared by laser cladding on nickel-based alloy, were heated using high frequency induction sources. The coating microstructure and the interface between bond coating and ceramic coating were characterized by SEM, XRD and EDS. The results show that two-layer substructure exists in the ceramic coating： one layer evolving from fully melted region where the sintered grains grow fully; another layer resembling the liquid-phase-sintered structure consisting of three-dimensional net where the melted Al2O3 particles are embedded in the TiO2-rich matrix. The mechanism of the two-layer substructure formation is also explained in terms of the melting and flattening behavior of the powders during laser cladding processing. The spinel compounds NiAl2O4 and acicular compounds Cr2O3 are discovered in the interface between bond coating and ceramic coating. It proves that the chemical reactions in the laser cladding process will significantly enhance the coating adhesion.
基金Project (11KJB430007) supported by the University Natural Science Research Program of Jiangsu Province, ChinaProject supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions, China
文摘The dielectric properties and phase transition characteristics of La2O3- and Sb2O3-doped barium strontium titanate ceramics prepared by solid state route were investigated. The microstructure was identified by X-ray diffraction method and scanning electron microscope was also employed to observe the surface morphologies. It is found that （La,Sb）-codoped barium strontium titanate ceramics exhibit typical perovskite structure and the average grain size decreases dramatically with increasing the content of Sb2O3. Both La3＋ ions and Sb3＋ ions occupy the A-sites in perovskite lattice. The dielectric constant and dielectric loss of barium strontium titanate based ceramics are obviously influenced by La2O3 as well as Sb2O3 addition content. The tetragonal-cubic phase transition of La2O3 modified barium strontium titanate ceramics is of second order and the Curie temperature shifts to lower value with increasing the La2O3 doping content. The phase transition of （La,Sb）-codoped barium strontium titanate ceramics diffuses and the deviation from Curie-Weiss law becomes more obvious with the increase in Sb2O3 concentration. The temperature corresponding to the dielectric constant maximum of （La,Sb）-codoped barium strontium titanate ceramics decreases with increasing the Sb2O3 content, which is attributed to the replacement of host ions by the Sb3＋ ions.
文摘The hip joint femoral head prosthesis was prepared using the Al2O3 material, which was synthesized by high purity alumina micro-powder and Mg- Zr- Y composite addhitives , the cold manufacturing techniques of lathe turning, grade polishing and the matching size correction of the sintered femoral head were studied. The results showed, after being pressed under 200 MPa cold isostatic pressure and being pre-sintered at 1150℃ , the biscuit＇ s strength can meet the demands of lathe turning ; After being grade polished by SiC micro-powder and diamond abrading agent and being size corrected by special instrument, the femoral head prosthesis of Al2O3 ceramic has good surface degree of finish and articulates tightly with femoral handle.
基金the Natural Science Fundation of Guangxi Province(No.0575104)the Guangxi Education Department Key Fund(No.2003-22)+1 种基金the Guangxi Fund of New Century Qualified Scholars(No.2002210)the National Science Foundation(No.50672016)
文摘Fe-Al intermetallic/TiC-Al2O3 ceramic composites were successfully prepared by selfpropagating high-temperature synthesis （SHS） from natural ilmenite, aluminium and carbon as the raw materials. The effects of carbon sources, preheating time and heat treatment temperature on synthesis process and products were investigated in detail, and the reaction process of the FeTiO3-Al-C system was also discussed. It is shown that the temperature and velocity of the combustion wave are higher when graphite is used as the carbon source, which can reflect the effect of the carbon source structure on the combustion synthesis; Prolonging the preheating time or heat treatment temperature is beneficial to the formation of the ordered intermetallics; The temperature and velocity of the combustion wave are improved, but the disordered alloys are difficult to eliminate with the preheating time prolonged. The compound powders mainly containing ordered Fe3Al intermetallic can be prepared through heat treatment at 750 ℃.
文摘The main Iimitation to the toughening of the α-Al2O3/Ni composite is the poor bonding atthe interface. which causes the nickel particles to be pulled-out during crack propagation with-out obvious plastic deformation. A proper control of oxygen content at the Al2O3-Ni interfacecan promote wetting at the intedece, and produce a mechanically interlocked and chemically strengthened intedece, causing most of the nickel particles to be stretched to failure and to expe-rience severe plastic deformation during crack propagation in the composite. Fracture toughnesstesting using a modified double cantilever beam method with in situ observation of crack prop-agation in a scanning electron microscope shows that the composite with the strengthenedinterface has a more desirable R-curve behaviour and a higher fracture toughness value than thenormal composite.
基金Project supported by the National Natural Science Foundation of China (Grant No.60578041)the National High Tech-nology Research and Development Program of China (Grant No.715-006-0060)
文摘The influences of the PbO-B2O3-CuV2O6 （PBC） additives on the microwave dielectric properties of （Pb0.5Ca0.5） （Fe0.5Nb0.5）O3 （PCFN） ceramics were investigated as a function of sintering temperature from 950 ℃ to 1 100 ℃. The sintering temperature of the specimens with the glass could be lowered from 1125 ℃ to 1 025℃ without the degradation of microwave dielectric properties. The microwave results showed that the dielectric constant cr was not significantly different while Qf values decreased with the increase of CuV206 content of PBC glass. For the specimens doped with PB-CV0.1 glass （81% PbO-9% B203-10% CuV2O6） and sintered at 1 025 ℃ for 3 h, the microwave dielectric properties of Qf=4 823 GHz, Cr=107.1 with TCF=＋15.03 ×10^-6/℃ were obtained.
文摘The 0.8Pb(Zr0.48Ti0.52)O3 – 0.125Pb(Zn1/3Nb2/3)O3 – 0.075Pb(Mn1/3Nb2/3)O3 + x wt% Fe2O3 ceramics (PZT-PZN-PMnN), where x = 0 ÷?0.35, has been prepared by two-stage calcination method. The effect of Fe2O3 content on the crystal structure and electrical properties of ceramics has been investigated. The results of X-ray diffraction (XRD) show that all samples have pure perovskite phase with tetragonal structure, the c/a ratio increases with increasing Fe2O3 content. At x = 0.25, electrical properties of ceramics are best: the density (r) of 7.86 g/cm3, the electromechanical coupling factor (kp) of 0.64, the dielectric constant (εr) of 1400, the dielectric loss (tand) of 0.003, the mechanical quality factor (Qm) of 1450, the piezoelectric constant (d31) of 155 pC/N, and the remanent polarization (Pr) of 37 μC/cm2, which makes it as a promising material for high power piezoelectric devices.
文摘We fabricated YBa2Cu3O7–d bulk ceramics with a domestic microwave oven and investigated the effect of pressure at the press procedure. If the pressure was not high enough, the ratio of BaCuO2 phase became large, estimated from x-ray diffraction (XRD) measurements. We found that the pressure should be 700 kgf/cm2 at least in order to suppress the BaCuO2 phase.
文摘The sintering temperature of Li2ZnTi3O8 ceramics is still high for LTCC-based applications. In this work, V2O5 was doped as the sintering aid. The sintered density, phase composition, grain size, as well as microwave dielectric properties of Li2ZnTi3O8 ceramics with the addition of V2O5 were investigated. Based on our research, V2O5 doping effectively promoted the densification of Li2ZnTi3O8 ceramics at about 900°C, without affecting the main crystal phase of the ceramics. Li2ZnTi3O8 ceramics with 0.5 wt% V2O5 doping (sintered at 900°C) exhibited the best microwave dielectric properties (Qf =?22,400 GHz at about 6 GHz, εr = 25.5, and τf = -10.8 ppm/°C). The V2O5-doped Li2ZnTi3O8 ceramics were well cofired with Ag inner paste without cracks and diffusion, indicating its significant potential for LTCC applications.
基金Supported by National High Technology Research and Development Program of China(No.2002AA2040).
文摘Polycrystalline 3Y-TZP/Al2O3 tetragonal zirconia fiber was obtained by the pyrolysis of gel fibers using zirconium oxychloride octahydrate（ZOC） as the raw material. The spinnable zirconia sol was prepared by electrolyzing the zirco-nium oxychloride octahydrate（ZOC） solution in the presence of acetic acid and sugar（ sucrose, glucrose or fructose） , in which the molar ratios of CH3 COOH/ZOC and sugar/ZOC were 1.0-4.0 and 0.2-0.4, respectively. The pre- pared tetragonal zireonia fibers sintered at different temperatures showed smooth and crack-free surfaces with diame, ters of 5-10 μm. The addition of Al2O3 enhanced the sintering process and prevented the crystals from growing. Thermogravimetric analysis（TG）, X-ray diffraction （ XRD ）, Fourier transform infrared spectroscopy（FTIR）, and scanning electron microscope（SEM） techniques were used to characterize the prepared fibers.
