scholarly journals Giant dielectric response in microwave processed CaCu3Ti4O12 ceramics: A correlation among microstructure, dielectric and impedance properties

2019 ◽  
Vol 13 (4) ◽  
pp. 387-400
Author(s):  
Buddhadev Samanta ◽  
Dipika Nanda ◽  
Pawan Kumar ◽  
Rashmirekha Sahu ◽  
Sujata Swain ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Grain Boundary ◽  
Sintering Temperature ◽  
Heterogeneous Systems ◽  
Secondary Phase ◽  
Rietveld Analysis ◽  
Boundary Region ◽  
Microstructural Investigation ◽  
Giant Dielectric ◽  
Different Temperatures

Polycrystalline CaCu3Ti4O12 (CCTO) ceramics was synthesized by microwave assisted solid-state reaction. Effect of sintering at different temperatures on the crystal structure, dielectric and impedance properties was investigated in detail. Rietveld analysis of X-ray diffraction data identified that crystal structure was a mixture of cubic CCTO and monoclinic CuO phases. Lattice parameters and amount of CuO secondary phase were also estimated as a function of sintering temperature. Microstructural investigation confirmed the existance and successive increase of the melted phase near the grain boundary region with increasing temperature of sintering. Cu-rich nature of the melted phase was further confirmed by selective area EDX spectra. Dielectric and impedance properties were studied as a function of frequency (100Hz to 1MHz) and temperature (room temperature to 300?C). Improvement in dielectric properties as a function of sintering temperature (1000 to 1050?C) was explained in terms of reduction in grain boundary dimension due to the successive increase in Cu-rich melted phase. However, dielectric constant started falling when sintered at 1075?C, which may be accounted in terms of segregation of large amount of CuO phase after a certain temperature and hence a non-stoichiometry of Cu in CCTO lattice. Impedance data were modelled by equivalent electrical circuits to investigate different contributions of electrically heterogeneous systems. In addition, probable relaxationmechanism has been discussed on the basis of impedance and modulus data. Activation energies were calculated from different characterizations and a non-Debye-type relaxation phenomena were observed. In this work, an attempt is made to build up a correlation among synthesis procedure, sintering temperature, dielectric, impedance and microstructural properties.

scholarly journals Phase Analysis of Bio-Based Derived Tricalcium Disilicate From 2CaO:1SiO2 By X-ray Diffraction

2021 ◽  
Vol 2129 (1) ◽  
pp. 012054
Author(s):  
Siti Nur Hazwani Yunus ◽  
Khor Shing Fhan ◽  
Banjuraizah Johar ◽  
Nur Maizatul Shima Adzali ◽  
Nur Hazlinda Jakfar ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Rice Husk ◽  
Single Phase ◽  
Sintering Temperature ◽  
Rietveld Analysis ◽  
Dicalcium Silicate ◽  
X Ray Diffraction ◽  
X Ray ◽  
Different Temperatures ◽  
Complete Formation

Abstract In this paper, tricalcium disilicate was formed from dicalcium silicate compound powder, synthesised via a mechanochemical technique using a stoichiometric 2CaO:1SiO2. Compound CaO and SiO2 were derived from the bio-waste of eggshell and rice husk at the calcination temperature of 900°C and 800°C, respectively. The dicalcium disilicate powder was sintered for 2 hours at different temperatures ranging from 1150°C to 1350°C. Using X-ray diffraction with Rietveld analysis, it was found that the amount of tricalcium disilicate with monoclinic (beta) crystal structure increases on sintering temperature at the expense of dicalcium silicate. The complete formation of single-phase tricalcium disilicate began at a sintering temperature of 1300°C. The effect of sintering temperatures on the crystallisation and phase transition of dicalcium silicate is reported. The size of crystallites depends on the sintering temperature. The finding of this study rebound to the benefit of society by reducing the risk-off pollution cause by accessive redundant bio-waste eggshell and rice husk and also reduced the amount of CaO and SiO2 used in the fabrication of Ca3Si2O7.

Effect of TiO2 Nanoparticle on the Structural and Electrical Properties of Nd0.67Sr0.33MnO3 /TiO2 Composites

2021 ◽  
Vol 317 ◽  
pp. 60-65
Author(s):  
Kean Pah Lim ◽  
Lik Nguong Lau ◽  
Amirah Natasha Ishak ◽  
Mohd Mustafa Awang Kechik ◽  
Soo Kien Chen ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Grain Boundary ◽  
Double Exchange ◽  
Secondary Phase ◽  
Solid State Reaction Method ◽  
Peak Shift ◽  
Boundary Region ◽  
Structural And Electrical Properties ◽  
Xrd Patterns ◽  
Grain Surface

In this work, (1-x) (Nd0.67Sr0.33MnO3): x (TiO2) composites with x = 0, 0.1, 0.2, 0.3 and 0.4 have been prepared to investigate the structural and electrical properties. Nd0.67Sr0.33MnO3 (NSMO) was synthesised via the solid-state reaction method before incorporated with TiO2. The addition of TiO2 nanoparticle as the secondary phase in manganite composite would favour the spin-polarized tunnelling near to the grain boundary and thus enhance the extrinsic magnetoresistance. Nevertheless, nanoparticle addition might contribute to substitution and diffusion with manganite compound as reported in literature. The effect of the TiO2 nanoparticle addition into NSMO composites has been examined by an X-ray diffractometer (XRD) and a four-point probe (4PP) system. From the thermogravimetric analysis (TGA), NSMO phase formation occurred in between 756.45 - 977.59 °C. XRD patterns showed that there is no peak shift when the TiO2 concentration increases. It can be deduced that TiO2 was segregated at the NSMO grain boundary region and its grain surface. However, a small amount of Ti atoms are expected to replace the Mn atoms in NSMO crystal system and has caused the increase in crystallite size. The electrical study showed that the presence of TiO2 nanoparticle and substitution of Ti in Mn sites have weaken the double exchange (DE) mechanism and suppressed the metal-insulator transition temperature (TMI). In addition, the insulating behaviour of TiO2 has also caused the resistivity of composites to increase drastically.

Structure of Carbonated Hydroxyapatite Based on Rietveld Method

2008 ◽  
Vol 368-372 ◽  
pp. 1187-1189
Author(s):  
Xu Ran ◽  
Jun Guo Ran ◽  
Li Gou ◽  
Ji Yong Chen ◽  
Jiao Min Luo
Keyword(s):  
Crystal Structure ◽  
Sintering Temperature ◽  
Rietveld Method ◽  
Rietveld Analysis ◽  
Structure Parameters ◽  
X Ray Diffraction ◽  
Carbonated Hydroxyapatite ◽  
X Ray ◽  
Quantitative Results ◽  
Distortion Index

The crystalline structures of B-type carbonated hydroxyapatite (CHA) powders sintered at 700, 900 and 1100°C, respectively, were studied by Rietveld analysis of powder X-ray diffraction (XRD) data. A series of structure parameters, including lattice parameters (a and c), bond length and the distortion index of PO4 tetrahedron (Dind) were calculated by Rietveld method to characterize the fine structure of CHA. The broadening effect of XRD reflections was separated to calculate the micro-strain and crystalline size. The results showed that CHA become more stable with the increase of sintering temperature, but the CO3 2- is almost lost at temperature of 1100°C. The quantitative results about crystal structure of CHA based on crystalline structure simulated by Rietveld method are obtained.

Densification Mechanism of SnO2 Ceramics Doped with 5.0 mol% MnO2

2007 ◽  
Vol 351 ◽  
pp. 88-92 ◽  
Author(s):  
Guo Qiang Luo ◽  
J. Li ◽  
Dong Ming Zhang ◽  
Qiang Shen ◽  
Lian Meng Zhang
Keyword(s):  
Grain Boundary ◽  
Oxygen Concentration ◽  
Manganese Oxides ◽  
Sintering Temperature ◽  
Heating Process ◽  
Pressureless Sintering ◽  
Cooling Process ◽  
Manganese Oxidation ◽  
Densification Mechanism ◽  
Different Temperatures

Dense SnO2 based ceramics are widely used. In this paper, 95SnO2-5MnO2 ceramics were prepared by pressureless sintering in air at different temperatures. Phase compositions and microstructures are examined by XRD, SEM and EDX, respectively. The SEM results show that different morphologies exist at the SnO2 grain boundary of ceramic, which compose of manganese oxidation, testified by EDX. The different manganese oxides phases, found by XRD, are the source of oxygen concentration at the grain boundary during heating and oxygen dissipation when cooling. However, solid solutions of Mn, Sn and O are not observed. The density of 95SnO2-5MnO2 ceramics decreases with increasing the sintering temperature, due to the evaporation of SnO and decreasing concentration of oxygen at grain boundary in the cooling process. Densification of the ceramic is promoted with inhibiting the decomposition of SnO2 by increasing oxygen concentration in the heating process, but it is limited by the dissipation of oxygen at the grain boundary in the cooling process.

scholarly journals Reactive sintering of B4c-TiB2 composites from B4 and TiO2 precursors

2020 ◽  
Vol 14 (4) ◽  
pp. 329-335
Author(s):  
Pavol Svec ◽  
Zuzana Gábrisová ◽  
Alena Brusilová
Keyword(s):  
Fracture Toughness ◽  
Boron Carbide ◽  
Titanium Diboride ◽  
Sintering Temperature ◽  
Secondary Phase ◽  
Ceramic Composites ◽  
Reactive Sintering ◽  
Different Temperatures ◽  
Carbide Matrix

The effect of sintering temperature in the interval from 1775 to 1850?C on the density, microstructure, hardness and fracture toughness of ceramic composites consisting of a boron carbide matrix and titanium diboride secondary phase was studied. The composites were hot pressed using in situ reaction between boron carbide and 40 wt.% of titanium dioxide additive. The samples were hot pressed at different temperatures but for the constant time of 60min, under the pressure of 35MPa in vacuum of 10 Pa. Both Vickers hardness and fracture toughness of the composites increased with the sintering temperature.Maximal hardness of 29.8GPa and fracture toughness of 6.9MPa?m1/2 were achieved for the composite with 29.6 vol.% of titanium diboride secondary phase sintered at the highest sintering temperature of 1850?C.

Effect of Sintering Conditions on the Phase Formation and Microstructure of Bi-2223/Ag/Ni Composite-Sheathed Tapes

2013 ◽  
Vol 745-746 ◽  
pp. 239-242
Author(s):  
Xing Pin Chen ◽  
Meng Liu ◽  
Xiao Wei Yu ◽  
Ming Ya Li
Keyword(s):  
Heat Treatment ◽  
Phase Formation ◽  
Microstructure Evolution ◽  
Significant Influence ◽  
Sintering Temperature ◽  
Secondary Phase ◽  
Secondary Phases ◽  
Different Temperatures ◽  
Sintering Conditions ◽  
Powder In Tube

Effect of sintering conditions in the first heat treatment on the phase and microstructure evolution of Bi-2223/Ag/Ni composite-sheathed tapes fabricated by powder-in-tube method was studied. Samples were sintered at different temperatures for different time in an atmosphere of 14.5% O2. The results showed that this higher O2 atmosphere improved the content of Bi-2223 phase. XRD and SEM results showed that Bi-2223 content increased with the extension of the dwelling time. Meanwhile, the sintering temperature had significant influence on the Bi-2223 content and secondary phase dimensions as well. With the increase of the sintering temperature, the Bi-2223 content reached to a maximum at 834. With further increase of sintering temperature, the Bi-2223 phase was decomposed to Bi-2212 and others secondary phases.

Phase Composition and Microstructure of Ca1–3xLn2xTiO3 (Ln=La, Nd, Sm) Ceramics

2012 ◽  
Vol 430-432 ◽  
pp. 36-40
Author(s):  
Bing Liang Liang ◽  
Yun Long Ai ◽  
Xing Hua Zheng ◽  
De Ping Tang ◽  
Fei He
Keyword(s):  
Crystal Structure ◽  
Phase Composition ◽  
Relative Density ◽  
Growth Pattern ◽  
Perovskite Structure ◽  
Sintering Temperature ◽  
Secondary Phase ◽  
Xrd Analysis ◽  
Structure Phase ◽  
Structure And Microstructure

Ca1–3xLn2xTiO3 (Ln=La, Nd, Sm; x=0.13, 0.20) ceramics were investigated systematically to dicuss the influences of sintering temperature, compositions, Ln3+ ions on its sintering property, crystal structure and microstructure. The results show that the dense ceramics were obtained in the sintering temperature range of 1300~1350 °C and the relative density reached over 97%. Sintering temperature was 50~150 °C lower than previous reports. Single orthogonal perovskite structure phase was formed except that a little secondary phase Sm2Ti2O7 was detected by XRD analysis when x=0.20 and Ln=Sm. The growth pattern of Ca1–3xLn2xTiO3 grains was terracing growth.

scholarly journals Evaluation of the Microstructure and the Electrochemical Properties of Ce0.8(1−x)Gd0.2(1−x)CuxO[1.9(1−x)+x] Electrolytes for IT-SOFCs

2020 ◽  
Vol 10 (13) ◽  
pp. 4573 ◽  
Author(s):  
Grazia Accardo ◽  
Jae Kwan Bae ◽  
Sung Pil Yoon
Keyword(s):  
Crystal Structure ◽  
Electrochemical Properties ◽  
Sintering Temperature ◽  
Sol Gel ◽  
Ionic Conductivities ◽  
Secondary Phase ◽  
Total Conductivity ◽  
Temperature Range ◽  
Copper Addition ◽  
Dense Bodies

The influence of copper addition (0.5–2 mol%) on the crystal structure, densification microstructure, and electrochemical properties of Ce0.8Gd0.2O1.9 synthesized in a one-step sol–gel combustion synthesis route has been studied. It has been found that Cu is very active as sintering aids, with a significative reduction of GDC firing temperature. A reduction of 500 °C with a small amount of copper (0.5 mol%) was observed achieving dense bodies with considerable ionic conductivities. Rietveld refined was used to investigate the crystal structure while relative density and microstructural examination were performed in the sintering temperature range of 1000–1200 °C after dilatometer analysis. High dense bodies were fabricated at the lowest sintering temperature, which promotes the formation of Ce0.8(1−x)Gd0.2(1−x)CuxO[1.9(1−x)+x] solid solution and the absence of secondary phase Cu-rich or the segregation or copper at the grain boundary. As compared to the pure GDC an improvement of total conductivity was achieved with a maximum for the highest copper content of 2.23·10−3–9.19·10−2 S cm−1 in the temperature range of 200–800 °C.

Effect of Sintering Temperature on Structure, Piezoelectric and Ferroelectric Properties of (Na0.5Bi0.5)0.90Ba0.10TiO3 Ceramic

2006 ◽  
Vol 317-318 ◽  
pp. 853-856 ◽  
Author(s):  
Qing Xu ◽  
X.L. Chen ◽  
S.J. Wu ◽  
Wen Chen ◽  
Hao Wang ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Piezoelectric Properties ◽  
Sintering Temperature ◽  
Ferroelectric Properties ◽  
Sintering Behavior ◽  
Poling Process ◽  
Different Temperatures ◽  
Ferroelectric And Piezoelectric Properties ◽  
Slight Deformation

Structures, ferroelectric and piezoelectric properties of (Na0.5Bi0.5)0.90Ba0.10TiO3 ceramic sintered at different temperatures were investigated. The results confirm an important role of sintering temperature on the structure and electrical properties of the ceramic. It was found that the increase of sintering temperature in the range of 1110-1160 promoted the development of crystal structure and microstructural densification, leading to an improvement in ferroelectric properties, poling process and piezoelectric properties. Further increase of the sintering temperature above 1160 resulted in a slight deformation of ceramic specimens. With respect to sintering behavior and piezoelectric properties, a relatively narrow sintering temperature range near 1150 was ascertained to be preferred for the ceramic.

High resolution STEM imaging study on high Tc superconductor YBa2CuaO7-x

1988 ◽  
Vol 46 ◽  
pp. 882-883
Author(s):  
H.-J. Ou ◽  
J. M. Cowley
Keyword(s):  
Crystal Structure ◽  
High Resolution ◽  
Grain Boundary ◽  
Strong Field ◽  
Imaging Study ◽  
Structure Defects ◽  
High Tc ◽  
High Tc Superconductor ◽  
Diffraction Patterns ◽  
Lattice Planes

Using the dedicate VG-HB5 STEM microscope, the crystal structure of high Tc superconductor of YBa2Cu3O7-x has been studied via high resolution STEM (HRSTEM) imaging and nanobeam (∽3A) diffraction patterns. Figure 1(a) and 2(a) illustrate the HRSTEM image taken at 10' times magnification along [001] direction and [100] direction, respectively. In figure 1(a), a grain boundary with strong field contrast is seen between two crystal regions A and B. The grain boundary appears to be parallel to a (110) plane, although it is not possible to determine [100] and [001] axes as it is in other regions which contain twin planes [3]. Following the horizontal lattice lines, from left to right across the grain boundary, a lattice bending of ∽4° is noticed. Three extra lattice planes, indicated by arrows, were found to terminate at the grain boundary and form dislocations. It is believed that due to different chemical composition, such structure defects occur during crystal growth. No bending is observed along the vertical lattice lines.

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