Synthesis, Structural and Dielectric Studies on SrBi2-xGdxNb2O9 Lead Free Ceramics

2020 ◽  
Author(s):  
Nitchal Kiran Jaladi ◽  
K. Sambasiva Rao ◽  
Haileeyesus Workineh ◽  
J. Anindhya Kiran ◽  
S. Nagamani
Keyword(s):  
Dielectric Properties ◽  
Single Phase ◽  
Xrd Analysis ◽  
Sem Analysis ◽  
Ion Concentration ◽  
Layered Perovskite ◽  
Cell Parameters ◽  
Lead Free Ceramics ◽  
Layered Perovskite Structure ◽  
Diffuseness Parameter

Abstract In this manuscript, the structural and dielectric properties of Gadolinium (Gd3+) substituted at Bi-site of SrBi2-xGdxNb2O9 (x= 0.0, 0.4, 0.6 and 0.8) prepared by using solid state reaction are studied. XRD analysis revealed the formation of single phase with orthorhombic structure in SBN and Gadolinium modified SBN. It is found that cell parameters and volume were decreased with increase of Gd3+ ion concentration in SBN. SEM analysis revealed that the samples possess well defined needle shaped grains. The grain size of SBN was hindered by the presence of Gd3+ ion at Bi-site. The growth of single phase layered perovskite structure was confirmed from FTIR and Raman spectroscopy. The dielectric properties of Gd3+ ion doped SBN ceramics are studied as a function of frequency (50Hz-1MHz) from room temperature to 500ºC. It is observed that phase transition temperature (Tc) decreased from 430ºC to 330ºC with increase of frequency due to incorporation of Gd3+ ion in SBN. The broadness of peaks and decrease in Tc indicate the transition from a normal ferroelectric to ferroelectric-relaxor type. The study on variation of tanδ with temperature at different frequencies indicates that tanδ has larger values at higher temperatures. Further, the diffuseness parameter (γ) has been computed for all the compositions.

Studies of the Average Valence State of the Transition Metals and the Electrical Properties of LaSr3Fe3-xMnxO10-δ (x=0.0-0.8) Mixed Conductors

2016 ◽  
Vol 852 ◽  
pp. 95-100
Author(s):  
Qin Li ◽  
Wei Bin Wan ◽  
Shuai Li ◽  
Zhi Bing Sheng ◽  
Guo Guang Zhang
Keyword(s):  
Transition Metals ◽  
Surface Potential ◽  
Valence State ◽  
Xrd Analysis ◽  
Layered Perovskite ◽  
Mixed Conductors ◽  
Kelvin Probe ◽  
Average Valence ◽  
Layered Perovskite Structure ◽  
Mn Content

LaSr3Fe3-xMnxO10-δ (x=0.0-0.8) mixed conductors with layered perovskite structure were prepared via citric acid method. XRD analysis showed that the cell volume decreased with Mn content. The fraction of Fe4+ concentration to the concentration of tetravalent ions decreased with the increase of Mn content. The decrease of average valence state (VB) of transition metals of LaSr3Fe3-xMnxO10-δ samples with the increase of temperature gave rise to the drop of p type charge carriers and the increase of oxygen vacancies. According to the relationship between VB and the numbers of the configurations of transition metals in LaSr3Fe3-xMnxO10-δ , the possible filling states of 3d orbitals of Fe and Mn ions at 700 °C and 800 °C were given. The variations of conductivities of LaSr3Fe3-xMnxO10-δ samples were interpreted on the basis of the variation of VB and δ with temperature and Mn content, respectively. Scanning Kelvin probe measurement results revealed that the surface potential of x=0.6 sample was the highest while x=0.8 sample was the lowest. The higher the surface potential, the higher the energy needed for an electron to be released from the sample.

scholarly journals Microwave Absorbing Properties of NiZnCu Ferrite and Polychloropren Composites

2020 ◽  
pp. 27-32 ◽  
Author(s):  
Priscila Richa ◽  
Roberto Costa Lima ◽  
Ana Paula Santiago de Falco ◽  
Ana Paula da Silva ◽  
Elvia Leal ◽  
...  
Keyword(s):  
Single Phase ◽  
Xrd Analysis ◽  
Sem Analysis ◽  
Magnetic Losses ◽  
X Ray Diffraction ◽  
X Ray ◽  
Microwave Absorbing Properties ◽  
Absorbing Materials ◽  
Military Applications

Radar-absorbing materials (RAMs) have been used in military applications for several decades to reduce radar detection of vessels and aircrafts. In the present work, the performance of Ni0.35Zn0.35Cu0.3Fe2O4 ferrite as a RAM is investigated. The ferrite was firstly synthesized by combustion reaction and then calcinated at 1200 °C for 1 h. Composites were prepared with 80:20, 70:30 and 60:40 concentrations in weight of ferrite:polychloroprene. The X-ray diffraction (XRD) analysis showed a single phase ferrite formation and the scanning electron microscopy (SEM) analysis of the composites showed a good dispersion of the ferrite in the polychloroprene matrix. The electromagnetic (EM) characterization of the composites revealed that the EM attenuation is mainly attributed to magnetic losses observed in the material. The 80:20 composite achieved the best performance and presented a reflectivity of -26.7 dB at 10.2 GHz.

Structure and Tc of La1−xYbxBa2Cu3O7-y Layered Perovskite Superconductors

1987 ◽  
Vol 99 ◽  
Author(s):  
C. Jiang ◽  
S. M. Green ◽  
YU Mei ◽  
H. L. Luo ◽  
C. Politis
Keyword(s):  
Rare Earth ◽  
Single Phase ◽  
The Other ◽  
Layered Perovskite ◽  
Superconducting Transition ◽  
Trivalent State ◽  
Layered Perovskite Structure ◽  
The Difference ◽  
Almost All ◽  
Tetravalent State

After the discovery of YBa2Cu3O7-y with an unusually high superconducting transition temperature (Tc), around 95 K [1], similar compounds were made by completely replacing Y by the other rare-earth elements. It was found that RBa2Cu3O7-y (RBCO; R = rare-earth) possessed the same orthorhombically distorted layered perovskite structure and virtually the same Tc for almost all R [2–8]. The exceptions are compounds with R = Ce, Pr and Tb. The stable tetravalent state of these three R elements, as contrasted with the stable trivalent state of the other R elements, may be the reason behind this problem [9]. But there are also problems in producing single-phase, high Tc samples with La, Yb and Lu substitutes [10–12]. One of the reasons for this may be the size of these R ions: the difference between their radii and that of Y3+ is comparably large. Here we present the results of our systematic study of the structure and transport properties of the series of compounds La1−xYbxBCO (0.05 ≤ × ≤ 0.95).

scholarly journals Mg2+ Doping Effects on the Structural and Dielectric Properties of CaCu3Ti4O12 Ceramics Obtained by Mechanochemical Synthesis

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1187
Author(s):  
Piotr Dulian ◽  
Wojciech Bąk ◽  
Mateusz Piz ◽  
Barbara Garbarz-Glos ◽  
Olena V. Sachuk ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Solid Solutions ◽  
Xrd Analysis ◽  
High Energy ◽  
Ion Concentration ◽  
Dielectric Study ◽  
X Ray Diffraction ◽  
Sintering Time ◽  
Doping Effects ◽  
Ball Milling Technique

In this study, ceramic CaCu3Ti4O12 (CCTO) and CaCu3−xMgxTi4O12 solid solutions in which 0.1 ≤ x ≤ 0.5 were prepared by the mechanochemical method, realized by a high-energy ball milling technique. The effects of the Mg2+ ion concentration and sintering time on the dielectric response in the prepared ceramics were investigated and discussed. It was demonstrated that, by the use of a sufficiently high energy of mechanochemical treatment, it is possible to produce a crystalline product after only 2 h of milling the mixture of the oxide substrates. Both the addition of magnesium ions and the longer sintering time of the mechanochemically-produced ceramics cause excessive grain growth and significantly affect the dielectric properties of the materials. The X-ray diffraction (XRD) analysis showed that all of the as-prepared solid solutions, CaCu3−xMgxTi4O12 (0.0 ≤ x ≤ 0.5), regardless of the sintering time, exhibit a cubic perovskite single phase. The dielectric study showed two major contributions associated with the grains and the grain boundaries. The analysis of the electric modules of these ceramics confirmed the occurrence of Maxwell–Wagner type relaxation, which is dependent on the temperature.

scholarly journals Single-phase multiferroics: new materials, phenomena, and physics

2019 ◽  
Vol 6 (4) ◽  
pp. 653-668 ◽  
Author(s):  
Chengliang Lu ◽  
Menghao Wu ◽  
Lin Lin ◽  
Jun-Ming Liu
Keyword(s):  
Colossal Magnetoresistance ◽  
Single Phase ◽  
Magnetoelectric Coupling ◽  
Layered Perovskite ◽  
New Materials ◽  
Emergent Phenomena ◽  
Hybrid Mechanisms ◽  
Layered Perovskite Structure ◽  
Novel Applications ◽  
New Phenomena

Abstract Multiferroics, where multiple ferroic orders coexist and are intimately coupled, promise novel applications in conceptually new devices on one hand, and on the other hand provide fascinating physics that is distinctly different from the physics of high-TC superconductors and colossal magnetoresistance manganites. In this mini-review, we highlight the recent progress of single-phase multiferroics in the exploration of new materials, efficient roadmaps for functionality enhancement, new phenomena beyond magnetoelectric coupling, and underlying novel physics. In the meantime, a slightly more detailed description is given of several multiferroics with ferrimagnetic orders and double-layered perovskite structure and also of recently emerging 2D multiferroics. Some emergent phenomena such as topological vortex domain structure, non-reciprocal response, and hybrid mechanisms for multiferroicity engineering and magnetoelectric coupling in various types of multiferroics will be briefly reviewed.

Microwave Dielectric Properties of Low-Fired Nd2Ti2SiO9 Ceramics with BaCu (B2O5) Addition

2014 ◽  
Vol 941-944 ◽  
pp. 509-512
Author(s):  
Guo Hua Chen ◽  
Xiao Ling Kang ◽  
Yun Yang
Keyword(s):  
Dielectric Properties ◽  
Firing Temperature ◽  
Single Phase ◽  
Microwave Dielectric Properties ◽  
Secondary Phase ◽  
Xrd Analysis ◽  
Sintering Behavior ◽  
Reaction Route ◽  
Conventional Solid State Reaction ◽  
Microwave Dielectric

Nd2Ti2SiO9 ceramics with low-firing temperature by BaCu (B2O5) addition were prepared by the conventional solid-state reaction route and the sintering behavior, phase purity, microstructure and microwave dielectric properties were investigated. The XRD analysis results show a single phase Nd2Ti2SiO9 is formed and no secondary phase is found. Addition of BaCu (B2O5) can effectively lower the firing temperature by about 150 °C. The Nd2Ti2SiO9 ceramics with 4wt% BaCu (B2O5) sintered at 1150 °C exhibit good microwave dielectric properties with a permittivity of 28.8, a Q×f value of 16110 GHz, and a temperature coefficient of resonant frequency of-12.3 ppm /°C, which is suitable for microwave communication applications.

Electrical Properties of Bismuth-Layered Structural CaxSr2-xBi4Ti5O18 Ceramics

2010 ◽  
Vol 105-106 ◽  
pp. 282-285 ◽  
Author(s):  
Su Hua Fan ◽  
Feng Qing Zhang ◽  
Q.D. Che ◽  
R. Yu ◽  
W. Hu ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Remnant Polarization ◽  
Single Phase ◽  
Ferroelectric Properties ◽  
Secondary Phase ◽  
Ferroelectric Ceramics ◽  
Layered Perovskite

Effects of amount of Ca on crystal structure, microstructure, ferroelectric properties, and dielectric properties of the CaxSr2-xBi4Ti5O18 (CSBTi-x) ferroelectric ceramics were investigated. The results show that single-phase layered perovskite ferroelectrics were obtained and no appreciable secondary phase was found.Ca-doping results in a notable enlargement of remnant polarization 2Pr. The 2Pr of CSBT-0.15 reaches a large value, the remnant polarization 2Pr and coercive field 2Ec were 18.1µC/cm2 and 120.2kV/cm, respectively. Dielectric constant and dielectric loss of CSBT-0.15 was also measured, showing dielectric constant εr=199~194 and dielectric loss tanδ=0.02~0.014 over the range of 100 kHz~1MHz, respectively.

Synthesis and Electrical Characterization of 0.8(K,Na)NbO3-0.2(Ba,Ca)(Zr,Ti)O3 Lead-Free Ceramics

2015 ◽  
Vol 1112 ◽  
pp. 15-18
Author(s):  
Nur Amaliya Rohmah ◽  
Nahariatul Hikmah ◽  
Suasmoro Suasmoro
Keyword(s):  
Single Phase ◽  
Electrical Characterization ◽  
Xrd Analysis ◽  
Solid State Reaction Method ◽  
Lead Free ◽  
Mixed Powder ◽  
Single Phase Sample ◽  
Lead Free Ceramics ◽  
Average Grain Size ◽  
Free Material

In this research, the physical and electrical properties of 0.8K0.5Na0.5NbO3-0.2Ba0.5Ca0.5Zr0.5Ti0.5O3(0.8KNN-0.2BCZT) were characterized. Lead-free material, 0.8KNN-0.2BCZT with and without alkaline excess was synthesized via solid state reaction method. KNN and BCZT were calcined at 700°C and 1200°C for 2 hours respectively and mixed by planetary milling. The mixed powder was recalcined at 1250°C for an hour then sintered at 1150°C, 1200°C and 1250°C for 2 and 4 hours. XRD analysis of 0.8KNN-0.2BCZT for excessive (8% Na, 2% K) sample sintered at 1150°C for 4 hours has single phase showing ABO3structure (A=K, Na, Ba, Ca and B=Ti, Zr, Nb) and multi phases for the other ones. The microstructure analysis (SEM) showed cubic-like grain shape in which excessive sample possessed greater average grain size than other. Dielectric properties and Curie temperature of single phase sample in this research were higher than those of pure KNN. The conductivity analysis reveals two regimes. The first regime (<300°C) showed no significant role of BCZT in KNN and the second one (>300°C) showed that BCZT increased conductivity of KNN and factor dissipation as well.

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