Table of Content

31 May 2010, Volume 44 Issue 05 Previous Issue    Next Issue

Metallography and Metallurgical Technology

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Flow Stress Behavior of Mg97Y2Zn1 Alloy during Hot Compression Deformation at Elevated Temperatures CHEN Bin，LU Chen，LIN Dongliang，ZENG Xiaoqin 2010, 44 (05):  593-0597.  Abstract ( 3868 )   Save The relationship among the flow stress, the deformation temperatures and the strain rates of Mg97Y2Zn1 magnesium alloy during hot compression deformation was investigated by using Gleeble3500 thermalmechanical simulator. And the corresponding flow stress model was established. The results indicate that the flow stress of the alloy decreases with increasing temperature at a given strain rate, and increases with increasing strain rate at a given temperature. The flow stress behavior of Mg97Y2Zn1 magnesium alloy during high temperature deformation can be represented by a ZenerHollomon parameter. The hot deformation activation energy of the alloy is 137.277 kJ/mol. Related Articles | Metrics

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Influence of Ti and Nb Microalloying on the Ductile to Brittle Transition Temperature of 18Cr-2Mo Ferritic Stainless Steel LIN Shu1,2，JIANG Laizhu2，ZHANG Ke1，ZHANG Zhixia2，RONG Yonghua1 2010, 44 (05):  598-0603.  Abstract ( 3907 )   Save 18Cr-2Mo ferritic stainless steel was fabricated by vacuum melting, forging, hot rolling and annealing. The effects of titanium (Ti) and niobium (Nb) on the ductile to brittle transition temperature (DBTT) of 18Cr-2Mo ferritic stainless steel were investigated by means of impact experiments and microscopy analysis, including transmission electron microscope (TEM), scanning electron microscope and electron backscatter diffraction (EBSD). The results indicate that the addition of Ti and Nb markedly lowers the DBTT (about 40 °C) under the condition of lower C and N content. The Ti and Nb microalloying results in the variation of texture type, namely, coexistence of (001) and (111) textures, in stead of (101) texture in 18Cr-2Mo without the addition of Ti and Nb elements, which are important factors to the decrease of DBTT. Further decrease of DBTT could be obtained by appropriate annealing processing. Fine TiN and NbC precipitated during hot rolling are the main reasons for the formation of the complex textures. Related Articles | Metrics

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Study on the Carburization Resistance of Cr25Ni35Nb and Cr35Ni45Nb Alloys for Ethylene Cracking Furnace Tube at High Temperature SHEN Limin,GONG Jianming,TANG Jianqun,JIANG Yong 2010, 44 (05):  604-0608.  Abstract ( 4351 )   Save Carburization kinetic curve of the two alloys (Cr25Ni35Nb and Cr35Ni45Nb) for ethylene cracking tubes was investigated and analyzed by the carburization experiments at elevated temperature (1 000 and 1 100 °C). Contents of Fe, Cr, Ni and Nb, growth of carburization layer, microstructure and composition of different zones of the two carburized materials were also studied by means of optical microscopy and scanning electron microscopy (SEM). The experimental results show that the carburization resistance of Cr35Ni45Nb alloy is better than that of Cr25Ni35Nb alloy; some locations on the surface of the specimens carburized during two cycling of time spall off and the spallation of Cr25Ni35Nb alloy is much more serious, this indicates that the thickness reduction of the ethylene cracking furnace tube will occur due to high temperature carburization and its strength and service life will be reduced. A mass of dispersive distributed secondary carbides generates in the zone of noncarburization to center zone of coupons, the density of which decreases with the distance increased from surface of coupon; at 1 100°C, the initial bone framework structural morphology of the two materials disappears after carburization and the secondary carbide along the grain boundaries spalls off after carburization. Related Articles | Metrics

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Internal Friction Analysis of Transformations in Au-Cu-Al Alloy JIN Mingjiang,GU Yijia,JIN Xuejun 2010, 44 (05):  609-0612.  Abstract ( 4039 )   Save The phase transformation in the asquenched and aged Au7Cu5Al4 alloys were investigated by internal friction technique. The results show that Ms temperatures of the asquenched and aged Au7Cu5Al4 alloys are -2.7 °C and 13.8 °C, respectively. The boundary relaxation activation energy for the quenched and aged Au7Cu5Al4 alloys were calculated for 131.5 kJ/mol and 93.0 kJ/mol, respectively, which indicates the difference of ordering states of the parent phases resulted by different thermal history. By high temperature internal friction measurement it is found that the B2→L21 ordering transition is interrupted by quenching and the parent phase state of quenched Au7Cu5Al4 alloy shows B2 ordering, which suppresses martensitic transformation. Related Articles | Metrics

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Determination of Dislocation Density in Nanostructured Bainitic Steels LI Hongyan,JIN Xuejun 2010, 44 (05):  613-0615.  Abstract ( 3876 )   Save The high dislocation density in nanostructured bainitic steels was verified by high resolution transmission electron microscopy (TEM). The dislocation density was measured by internal friction. The result shows that average dislocation density in nanostructured bainite is about 6.4×1015 m-2 using internal friction with medium frequency. Related Articles | Metrics

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Effect of Predeformation on Damping Capacity of Fe-19Mn and Fe-19Mn-1.5Si Alloys HUANG Shuke1,2,ZHOU Danchen1,LIU Jianhui1,LI Changan1,LI Ning2,WEN Yuhua2( 2010, 44 (05):  616-0620.  Abstract ( 3817 )   Save The effect of predeformation on damping capacity of Fe19Mn and Fe19Mn1.5Si alloys was studied. The damping capacity was measured using reversal torsion pendulum with free decay method. The stacking fault probability was determined by means of XRD (Xray diffraction). The microstructure was observed using OM (optical microscope). The results indicate that with the tensile strain increasing (0%-10%), the stacking fault probability in γaustenite and εmartensite of Fe19Mn alloy increases continually. When the tensile strain is above 4%, however, Shockley partial dislocations are cut into several segments because of the reciprocal chiasm of stacking faults and perfect dislocations gliding, so the distance of two strong points decreases. The damping capacity of Fe19Mn alloy, therefore, is improved with the tensile strain increasing until it reaches maximum at 4%, and then decreases. But it is not the same regularity to Fe19Mn1.5Si alloy when tensile strain is above 4%. The εmartensite and stacking faults are small before deformation, so the predeformation can not change the microstructure of Fe19Mn1.5Si alloy and the damping capacity does not decrease when tensile strain is above 4%, but is still increasing stably. Related Articles | Metrics

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Study on Internal Friction of Ageing Process of High Mn Austenite Hot Work Tool Steel MIN Na,XUE Chang,TONG Qian,WANG Hongbin,WU Xiaochun 2010, 44 (05):  621-0623.  Abstract ( 4076 )   Save The investigation on the ageing of austenite hot work tool steel by internal friction shows that the height of the peak dumps and the width of the peak narrows after ageing at 720 °C×2 h and 550 °C×10 h, compared with before ageing. The result reveals that the carbon atoms which are solved in the austenite lattice are repartitioned during aging, and the content of the alloy in the austenite matrix phase reduces. By analyzing the kinetic age combining JMA equation shows that at the beginning of the low temperature aging, there is a planar flow of interstitial atoms from the austenite lattice to interface and defect, while during the high temperature aging process, the interstitials and the solved alloy atoms in austenite lattices form carbide and grow centered on the defects. Related Articles | Metrics

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Mechanical Spectroscopy Characterization of Forming Property of Automobile Steel Sheets YU Ning1,LIU Yonggang2,ZHANG Zhibo1,ZHAN Hua2,ZHANG Jian2，JI Jingwen1 2010, 44 (05):  624-0627.  Abstract ( 3866 )   Save The internal friction in low carbon aluminium killed DC01 automobile steel sheets, which are of normal without superlower yield point, and of inhomogeneous stamping deformation containing Lüders bands and/or orange skin, were measured from room temperature to 350°C. It is found that for the automobile sheets with different stamping performancies their mechanical spectra have obviously different characterstics. There is a mechanical spectrum with three small peaks for the normal sheet, and there appears a doublepeak spectrum in which the two peaks are all obviously high for the sheet with Lüders bands, and there is a multipeak spectrum having 4 to 5 very small peaks for the sheet with orange skin. The discussion on the nature of the damping peaks and the characteristic of the mechanical spectra was made. Related Articles | Metrics

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Amplitude Effect of Internal Friction in γ-MnFe Alloys GU Suyi1,ZHANG Jihua2 2010, 44 (05):  631-0634.  Abstract ( 4180 )   Save An investigation was made regarding the variation in internal friction and modulus with 86.4%Mn and 80.8%Mn γMnFe alloys. The results indicate that γMnFe alloys undergo paramagnetic to antiferromagnetic transition and martensitic transformation while cooling from high temperature. There are three internal friction peaks during this process and they all have amplitude effect. It confirms that the twins caused by anteferromagnetic transition and martensitic transformation are the physical nature of high damping capacity of γMnFe alloys. Related Articles | Metrics

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Effects of Tempering on Microstructure and Mechanical Properties of Nonquenched and Tempered Bainite SG Steel WANG Hongbin，XUE Chang，PENG Jinming，LUO Yi，WU Xiaochun 2010, 44 (05):  635-0639.  Abstract ( 3769 )   Save The strengthening and toughening mechanism of nonquenched and tempered bainitic SG steel with tempered at 350 °C was studied by low frequency mechanical spectrum apparatus, scanning electronic microscope, transmission electronic microscope and JMatPro software. By the Snoek and SKK peaks in the internal friction depended on temperature and microstructure analysis, the distribution and precipitation behavior of carbon atoms in the bainitic ferrite and decomposition law of islandlike matensite/austenite were discussed. The results show that the intensity of Snoek in SG steel is very low and bainitic ferrite contains a few solid solution content of carbon atoms; and the yield strength of SG steel with tempered at 350 °C for 2 h is the highest, which is due to the precipitation strengthening from Cr7C3 and dislocation strengthening. Related Articles | Metrics

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Analysis on Internal Friction in Quenched and Tempered Hot Work Steel XUE Chang，WANG Hongbin，WU Xiaochun，SONG Wenwen 2010, 44 (05):  640-0644.  Abstract ( 3868 )   Save The internal friction spectrum of hot die steel Dievar with quenched into oil and tempered at different temperature was studied. The internal friction spectrum is decomposed into two peaks and background internal friction for quenched steel. One peak is attributed to stressinduced microdiffusion of carbon in martenstic alloy steel at 157.2 °C. The 225.5 °C peak named SKKpeak is related to the interactions between carbon atoms and dislocations. When the mount of carbon in solid solution is reduced by tempering the specimen at an elevated temperature, the height of the peak lowers and the peak shifts to a higher temperature. Some carbides nucleate and grow at dislocations, which induces stress relaxation. Relaxation time increases by the length of dislocation growed. The movement of the internal friction peak position is attributed to the effects of alloying elements and carbon atoms. Related Articles | Metrics

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Analysis of the DiffusionInduced Stresses of a Cylinder during Carburization QIN Xiaoyan,GONG Jianming,GENG Luyang 2010, 44 (05):  645-0649.  Abstract ( 4003 )   Save The diffusion process of constant surface concentration of carbon from inner wall toward outer surface was studied based on the Fick’s law. The formulas of the stresses induced by carbon diffusion in the cylindrical structure for the case of plain strain were derived using solid mechanics theory. The distribution of radial stress, circumferential stress and axial stress induced by carburization was investigated. The results show that for a given cylindrical structure the concentration increases with time extended. The radial stress component is compressive all the time. The circumferential stress has the maximum value at the inner surface of cylindrical structure at the initial. The state of circumferential stress is compressive in the region near inner surface and tensile near outer surface. The trend of the axial stress distribution is similar to the circumferential stress. The analysis also shows that the ratio of outer radius to inner radius of cylindrical structure has an effect on the distribution of carbon concentration and stresses. Related Articles | Metrics

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Investigations on Mechanisms of the Internalfriction Peak of Firstorder Phase Transformation in Solids YANG Kaiwei1,SHUI Jiapeng2,ZHU Zhengang2 2010, 44 (05):  650-0654.  Abstract ( 4517 )   Save Experimental study was carried on the crystallization of amorphous Pd43Ni10Cu27P20 ordereddisordered type phase transformation, nonproliferation of displacementtype phase transformation of shape memory alloy CuAlMn, and eutectoid phase transformation eutectoid ZnAl alloy. The simultaneous measurements of resistance and internal friction of three kinds of materials were designed and completed. And the frequency curve of internal friction at different temperatures was obtained by using interpolation. The results show that the internal frictiontemperature curve is not the relaxationtype internal friction peak, but the response to abrupt change of the relaxation parameters. The height of internal friction peak is related to the degree of relaxation. During low temperature range, structural relaxation is observed, and structural instability and structural relaxation can be used for qualitative interpretation of the influence of heating rate on the height of internal friction peak of phase transformation. Related Articles | Metrics

Physics

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Effect of Gradient Stress on the Dielectric Constant of BaTiO3 Film LI Liben,CHEN Qingdong,LI Xinzhong,ZHEN Zhiqiang,HU Zhixiang 2010, 44 (05):  655-0658.  Abstract ( 3581 )   Save A set of gradient stress was obtained by solving the elastic mechanical equations and used to Landau thermodynamic theory to explain the diffuse dielectric anomaly of BaTiO3 film grown on a tensile substrate. The results predict that a and aaphase may coexist in the film. The hysteretic spontaneous polarization behavior of the film can not be revealed for the inplane polarization exists for the two phases. The temperature dependence of outplane dielectric constant agrees with the experimental result. Related Articles | Metrics

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Comparative Studies of Mechanical Spectra of Glycerol by Single and Double Layer Depositing CompositeReed Vibration Methods YUAN Yinghan，YING Xuenong，ZHU Jinsong 2010, 44 (05):  659-0661.  Abstract ( 4045 )   Save A method was designed to measure the mechanical spectrum of materials from liquid to solid state in a composite reed vibration system. More experiments were performed to check the reliability of this method with the variation of deposited area. Negligible differences in the spectra are found with different deposited areas. However, a clear distinction is observed between single layer and double layer depositing. Considering the results of both cooling and subsequent heating routes, it seems more reliable using double layer depositing. Related Articles | Metrics

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Internal Friction of the Phase Transition of Ge2Sb2Te5 Thin Film 2010, 44 (05):  665-0669.  Abstract ( 3940 )   Save Related Articles | Metrics

Physics

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Study on Internal Friction of Pure Al Bicrystals with Tilt and Twist Grain Boundaries JIANG Weibin，KONG Qingping，CUI Ping，FANG Qianfeng 2010, 44 (05):  665-0669.  Abstract ( 2937 )   Save The internal friction of <111> tilt and twist grain boundaries in pure Al bicrystals with different misorientations was studied. The measured activation parameters of twist grain boundaries are different from those of tilt grain boundaries, which was explained by the difference of grain boundaries microstructure. With the help of a coupling model, the basic relaxation processes of different types of grain boundaries were suggested. In addition, when the misorientation angles of both tilt and twist grain boundaries are near to 60°, the grain boundarie internal friction peak does not appear, indicating that both coherent and incoherent near to 60° grain boundaries are highly resistant to stressinduced motion. Related Articles | Metrics

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Progress in the Studies of Structural Changes in Polymer Liquids by Mechanical Spectroscopy ZHU Zhengang,WU Xuebang,ZHOU Xuemao,LIU Changsong 2010, 44 (05):  669-0674.  Abstract ( 3630 )   Save The recent progress in the investigation of structural changes in polymer liquids (i.e. polymer melts and concentrated solutions) by mechanical spectroscopy was reviewed. The effects of molecular weight and composition of polymer blends on the liquidliquid transition were analyzed, and the mechanism of the liquidliquid transition was clarified. The relationships between the phase behaviors of concentrated aqueous solutions of poly (ethylene oxide)poly(propylene oxide)poly(ethylene oxide) (PEOPPOPEO) and temperature, concentration and the addition of NaCl were presented. The outlook on some of the most promising areas that being studied through mechanical spectroscopy in the area of soft matter was also pointed out. Related Articles | Metrics

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Mechanical Spectroscopy Investigation of Poly(vinyl acetate) Melt WU Xuebang,ZHU Zhengang,ZHOU Xuemao,LIU Changsong 2010, 44 (05):  675-0678.  Abstract ( 3700 )   Save The molecular relaxation dynamics in poly(vinyl acetate) (PVAc) was studied by mechanical spectroscopy above the glass transition temperature (Tg). The temperaturedependent mechanical spectra reveal the existence of two relaxation modes: α, ascribed to the glass transition, and α′, which might be related to the liquidliquid transition. The relaxation time follows VogelFulcherTamman law for both of the relaxation modes. A detailed analysis of the frequencydomain spectra above Tg shows a dynamic crossover at temperature TB ≈387 K through the temperature dependence of relaxation time, relaxation strength, and shape parameter. According to the phenomenological coupling model, the crossover is suggested to be caused by the strong increase of intermolecular cooperativity below TB with decreasing temperature. Related Articles | Metrics

Electrotechnology

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Characteristic of Mechanical Spectra and Electronic Transport Property of LiCoO2 Ceramic OU YANG Hongqun，LIU Wenfeng，SANG Mao，CHEN Lan，ZHU Ke，XIONG Xiaomin 2010, 44 (05):  679-0682.  Abstract ( 3697 )   Save LiCoO2 ceramics were synthesized by solid state reaction. An internal friction peak of phase transition type was observed around 170 K for LiCoO2 ceramics via dynamic mechanical analysis (DMA) in the temperature range of 123-573 K, which corresponds to the turning point in the plot of the logarithm of conductivity versus the inverse of temperature (ln σ-1/T). It shows that the phase transition at 170 K could change the electronic transport property and the activation energy doubles in the high temperature portion in LiCoO2 . Related Articles | Metrics

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Internal Friction on the Lithium Ion Conductor Li5La3Ta2O12 WANG Weiguo1，WANG Xianping2，GAO Yunxia2，FANG Qianfeng2 2010, 44 (05):  687-0691.  Abstract ( 3723 )   Save An investigation was made regarding the variation in internal friction and relative modulus with Li5La3Ta2O12 compound by means of force vibration. Two apparent relaxation internal friction peaks were observed. By fitting the data with two Debye peaks, the activation energy and preexponential factor of the peaks are deduced as 0.8-1.1 eV and 10-14-10-26 s, respectively, which indicates the occurrence of mutual interaction between the relaxation species (lithium vacancies). By fitting the data with the coupling model, the activation energy is deduced as 0.6-0.7 eV, close to the activation energy of lithium ion conductivity. Considering the crystal structure of Li5La3Ta2O12 compound, these two peaks are associated with the lithium ion diffusion between adjacent 48g24d sites and 48g48g sites, respectively. The peaks gradually shift toward higher temperature and increase in both height and activation energy when the sample is aged at room temperature in air. Combined with the change of sample’s mass, XRD and TGA, it can be concluded that the protons from the moisture substitute the lithium ions initially occupied the 48g sites in Li5La3Ta2O12 compound to form Li2O and new protonic derivatives, Li5-xLa3Ta2O12-x(OH)x (0<x≤2.15). Related Articles | Metrics

General Industrial Technology

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Origin of the Internal Friction Peak and Dynamics ofPhase Interfaces in Relaxor Ferroelectric PMN-15PT WANG Haiyan，CHEN Lan，XIONG Xiaomin，ZHANG Jinxiu 2010, 44 (05):  696-0700.  Abstract ( 4116 )   Save The dynamic dissipation behaviors of boundaries of polar nanoregions (PNRs) in PMN-15PT ceramics were investigated via internal friction and modulus measurements. An internal friction peak depended strongly on the variation rate of temperature θ and applied vibrating frequency f was observed in the temperature range of relaxor ferroelectrics. The nature of the internal friction peak was suggested to be associated with the dynamic process of the motion of PNRs’ boundaries driven by the variation of temperature and the feature of PNRs’ boundaries could be described by the dissipation function model proposed for the phase interface dynamics of firstorder phase transition. By comparison to other kinds of ceramic samples with normal sized phase interface, it was found that the interface of PNRs is a class of soft interface with small dynamic restoring coefficient and weak interaction between the interfaces and applied driven field. Related Articles | Metrics

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Preparation and Performance of Li5La3Ta2O12 Particulate Reinforced High Damping Aluminum Composites WANG Xianping1,2，WANG Weiguo2，LI Chun1，CHENG Zhijun2，FANG Qianfeng1,2 2010, 44 (05):  701-0703.  Abstract ( 3188 )   Save The metal matrix ceramic composite,Li5La3Ta2O12/Al, was prepared by powder metallurgy method. It was found that the damping capacity and the mechanical properties of the composite at room temperature are greatly enhanced in comparison with the pure Al. The damping capacity of the 20%Li5La3Ta2O12/Al composite can reach 0.010, which is one order of magnitude higher than that of pure Al, and the corresponding yield strength and microhardness of the composite are 43% and 28% higher than those of pure Al, respectively. Related Articles | Metrics

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Preparation and Damping Capacities of SiCp/Mg-Zn-ZrComposites PAN Anxia,MA Liqun,ZHANG Ping,XIA Mingliu，CHENG Jianghui，DING Yi 2010, 44 (05):  704-0707.  Abstract ( 3283 )   Save SiC particulate reinforced Mg-Zn-Zr composites were prepared by stir casting. The relationship of the compressive strength and the damping capacities of SiCp/Mg-Zn-Zrcomposites to the size of SiC particles was investigated. The results show that the compressive strength of the magnesium matrix composites can be improved when the SiC particles with an average size of 10 μm are added. The damping capacities of the composites with an average SiC particles size of 20 μm are better than those of the other composites. Related Articles | Metrics

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The Damping Capacities Effect on NiTi Film to PZT Material LU Xuemei,LIU Qingsuo,HE Xuankun,ZHANG Yujiao 2010, 44 (05):  708-0710.  Abstract ( 3723 )   Save PZT/NiTi composites were prepared by the method of depositing NiTi films on the PZT substrates by magnetron sputtering method. The phase structure and heterostructure of the composites were examined by using X-ray diffraction (XRD) and scanning electron microscope (SEM). A phase method was utilized to research on the damping capacities of PZT/NiTi composites. The results show that the change of damping capacities of PZT/NiTi composites is consistent with PZT, besides appearing a fancy platform about damping value. Related Articles | Metrics

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High Damping SiO2Coated LiNbO3 Particles Reinforced ZL102 Composites and Piezo-damping Features WENG Wei,WANG Haowei,MA Naiheng 2010, 44 (05):  711-0714.  Abstract ( 3560 )   Save LiNbO3 piezoelectric particles of high Curie point coated by SiO2 via solgel method were used and then LiNbO3(SiO2)/ZL102composites were fabricated through pressure infiltration. Damping properties from 30 °C to 350 °C were measured by dynamic mechanical thermal analyzer (DMTA). The results reveal that the damping capacity of LiNbO3(SiO2)/ZL102 composite is three times the value of ZL102 alloy and two times as high as LiNbO3/ZL102 composite at 30 °C. And with increasing temperature the damping capacities of three types of materials increase together and gradually become close. In the present paper, piezo-damping was achieved by using poled LiNbO3 piezoelectric particles. Moreover, the piezodamping was enhanced by SiO2 coatings, which changed the resistivity around LiNbO3 particles. Related Articles | Metrics

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Conductance of Like Perovskite Structure ACu3Ti4O12 Materials ZHOU Xiaoli 2010, 44 (05):  715-0717.  Abstract ( 3375 )   Save CaCu3Ti4O12 and La2/3Cu3Ti4O12 materials were prepared by solid reaction process, and the conductance properties were measured and studied. The experimental data show that the conductancetemperature curves of CaCu3Ti4O12 and La2/3Cu3Ti4O12 are similar. In the lower temperature range (<150 K), the conductance increases with the temperature and the samples exhibit negative resistancetemperature properties. In the temperature range of 150－170 K, the conductance reaches its maximum. Then, in the higher temperature range (170－250 K), the conductance decreases with the temperature. But the maximum value of conductance of CaCu3Ti4O12 is about 3 times larger than that of La2/3Cu3Ti4O12. Further analysis shows that after Ca 2＋ is replaced by La 3＋, onethird of vacancies remain in A sites, which results in the activation energy of La2/3Cu3Ti4O12 reaching 1.01 eV. The higher activation energy is the main cause of lower conductance of La2/3Cu3Ti4O12. Related Articles | Metrics

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Study on Dielectric Properties and Internal Friction of CaCu3Ti4O12 Ceramics WEI Naxin，ZHOU Xiaoli 2010, 44 (05):  718-0720.  Abstract ( 3405 )   Save CaCu3Ti4O12 ceramics were fabricated by solidstate reaction method. The dielectric properties and internal friction were measured by impedance meter. The results show that the internal friction of CaCu3Ti4O12 ceramics reaches its maximum at a certain temperature under a given frequency, and decreases rapidly when being offset from the temperature. On the other hand, there is a shift of internal friction to the high temperature region with the frequency increasing. A further study shows that the dielectric constant of the ceramics is smaller at a low temperature, but it suddenly changes at a certain temperature, then keeps the higher value with the increase of temperature. Meanwhile, the corresponding temperature for the sudden change increases with the frequency. The giant dielectric constant of CaCu3Ti4O12 has some relation with the intrinsic structure and barrierlayer capacitance, and the mutual dependence relations between the internal friction, frequency and the temperature are adapted to the polarization model, in which the sudden change induced by the dielectric constant under a certain temperature is related to the characteristic of the polaron. Related Articles | Metrics