http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
- 中文 을 입력하시려면 zhongwen을 입력하시고 space를누르시면됩니다.
- 北京 을 입력하시려면 beijing을 입력하시고 space를 누르시면 됩니다.
RISS 인기검색어
- 검색키워드
- 저자 : Sujata Sanghi (검색결과 3 건)
- 무료
- 기관 내 무료
- 유료
-
Rietveld refinement and impedance spectroscopy of calcium titanate
Monica Sindhu,Neetu Ahlawat,Sujata Sanghi,Ashish Agarwal,Reetu Dahiya,Navneet Ahlawat 한국물리학회 2012 Current Applied Physics Vol.12 No.6
Single phase perovskite CaTiO3 has been synthesized by conventional solid state reaction technique. The ceramic was characterized by XRD at room temperature and its Rietveld refinement inferred orthorhombic crystal structure with the space group Pbnm. The field dependence of dielectric relaxation and conductivity was measured over a wide frequency range from room temperature to 673 K. Analysis of Nyquist plots of CaTiO3 revealed the contribution of many electrically active regions corresponding to bulk mechanism, distribution of grain boundaries and electrode processes. The dc conductivity depicted a semiconductor to metal type transition. Frequency dependence of dielectric constant (ε') and tangent loss (tan δ) show a dispersive behavior at low frequencies and is explained on basis of Maxwell-Wagner model and Koop’s theory. Both conductivity and electric modulus formalisms have been employed to study the relaxation dynamics of charge carriers. The variation of ac conductivity with frequency at different temperatures obeys the universal Jonscher’s power law (σac α ωs). The values of exponent ‘s’ lie in the range 0.13 ≤ s ≤ 0.33, which in light of CBH model suggest a large polaron hopping type of conduction mechanism.
-
Navneet Singh,Ashish Agarwal,Sujata Sanghi 한국물리학회 2011 Current Applied Physics Vol.11 No.3
Spinel ferrites having compositions Zn_0.5Li_(1-2x)Mg_xFe_2O_4 (0 ≤ x ≤ 0.5) have been prepared by sol-gel auto combustion technique. The dielectric properties of these ferrites have been studied using impedance measurements in the frequency range 10 Hz―10 MHz and in the temperature range 310―473 K. The effect of temperature, frequency and composition on dielectric constant (ε´), dielectric loss (tanδ) and conductivity (σ) have been discussed in terms of hopping of charge carriers (Fe^2+↔Fe^3+). The occurrence of peak in the dielectric loss (tanδ) spectra is found to be temperature and composition dependent. The electrical modulus formulism has also been employed to study the relaxation dynamics of charge carriers and the results indicate the presence of non-Debye type of relaxation in these ferrites. Identical values of activation energy for dc conduction (E_dc) and for conductivity relaxation (E_M˝) reveal that the charge carriers have to overcome the same energy barrier while conducting and relaxing. A single ‘master curve’for normalized plots of all the modulus isotherms observed for a given composition indicates the temperature independence of dynamical process for charge carriers in the present ferrites. The absence of hysteresis and non-attainment of saturation magnetization (even at 8 kOe) suggests the super paramagnetic behaviour of these ferrites.
-
Jogender Singh, Ashish Agarwal,Ashish Agarwal,Sujata Sanghi,Tanvi Bhasin,Manisha Yadav,Umesh Bhakar,Ompal Singh 한국물리학회 2019 Current Applied Physics Vol.19 No.3
Multiferroics having composition Bi0.80-xBa0.20HoxFeO3 (BBFO, BBHFO5, BBHFO10, BBHFO15 and BBHFO20 for x=0.0, 0.05, 0.10, 0.15 and 0.20 respectively) were synthesized by method of solid state reaction. The crystal structure has been studied using X-ray diffraction technique. The X-ray patterns show enormous transform in crystal structure at concentration x=0.20. The Rietveld refinement of XRD patterns indicates that at concentration x=0.0 sample have rhombohedral structure with R3c space group while for the concentration x=0.05, 0.10, 0.15 and 0.20, the mixed phase including rhombohedral R3c and triclinic P1 space groups were obtained with best fitting. This phase transformation in crystal structure is observed due to mismatching of ionic radii of doped ions and parent ions. Magnetic properties of all samples were carried out by using vibrating sample magnetometry. M-H hysteresis loops shows that with doping of Ba and Ho antiferromagnetic BiFeO3 (BFO) transforms into ferromagnetic. The dielectric and ferroelectric measurements were carried out which shows that dielectric constant, dielectric loss and ferroelectric properties are enhanced with co-doping of Ho in comparison of the pristine BFO due to structure deformation and decrease in oxygen vacancies with higher concentration of Ho. Significant improvement has been observed in dielectric constant and remnant magnetization values with increasing content of Ho and decrease in the dielectric loss.
연관 검색어 추천
이 검색어로 많이 본 자료
활용도 높은 자료
