Raffaella Lo Nigro; Emanuela Schilirò; Patrick Fiorenza; Fabrizio Roccaforte
Abstract
Plasma Enhanced Atomic Layer Deposition (PEALD) technique has been used for the fabrication of nanolaminated Al2O3-HfO2 thin films as well as of single Al2O3 and HfO2 layers on silicon substrates. The three different layers, i.e. Al2O3, HO2 and the nanolaminated Al2O3-HfO2 thin films, which consists ...
Read More
Plasma Enhanced Atomic Layer Deposition (PEALD) technique has been used for the fabrication of nanolaminated Al2O3-HfO2 thin films as well as of single Al2O3 and HfO2 layers on silicon substrates. The three different layers, i.e. Al2O3, HO2 and the nanolaminated Al2O3-HfO2 thin films, which consists of very thin alternating layers of Al2O3 and HfO2, have been deposited at temperature as low as 250°C. Each of them possesses a total thickness of about 30 nm and has been tested as possible dielectric for microelectronics devices. In particular, the structural properties and their evolution upon annealing treatment at 800°C have been investigated. Moreover, the dielectrical properties of the nanolaminated system have been compared to the opposite single Al2O3 and HfO2 layers. The collected data pointed out to promising properties of the fabricated nanolaminated film. Copyright © VBRI Press.
Kumara Raja Kandula; Sai Santosh Kumar Raavi; Saket Asthana
Abstract
Nd 3+ -substituted lead free 0.94(Na0.5Bi0.5-XNdXTiO3)-0.06BaTiO3 (x=0, 0.01) ceramics were synthesized by using conventional solid state route. The XRD studies revealed the phase purity and existence of the monoclinic (Cc), cubic (Pm3m) along with the minor tetragonal phases confirmed with help of structural ...
Read More
Nd 3+ -substituted lead free 0.94(Na0.5Bi0.5-XNdXTiO3)-0.06BaTiO3 (x=0, 0.01) ceramics were synthesized by using conventional solid state route. The XRD studies revealed the phase purity and existence of the monoclinic (Cc), cubic (Pm3m) along with the minor tetragonal phases confirmed with help of structural refinement. The electrical poling field induces the structural modification to rhombhohedral (R3c), cubic (Pm3m) along with the minor tetragonal phase (P4mm). The dielectric measurements revealed the relaxor behavior. The coercive field drops remarkable and there is slight improvement in the polarization with the substitution of Nd as compared to the pure 0.94(Na0.5Bi0.5TiO3)-0.06BaTiO3. The luminescence occurred from the optically active element Nd 3+ under the influence of the average crystal symmetry of 0.94(Na0.5Bi0.5TiO3)-0.06BaTiO3. The luminescence quenching observed without any shift in position upon the poling supports the observation of higher symmetric structure.
Sandeep Kumar; Neetu Ahlawat; Navneet Ahlawat
Abstract
In the present work, the results of microstructure, dielectric and ferroelectric investigation of microwave sintered CaCu3Ti4O12 (CCTO) ceramic with different heating rate are presented. Scanning electron micrographs revealed that grain size decreases from 1.167 µm to 0.744 µm with increased ...
Read More
In the present work, the results of microstructure, dielectric and ferroelectric investigation of microwave sintered CaCu3Ti4O12 (CCTO) ceramic with different heating rate are presented. Scanning electron micrographs revealed that grain size decreases from 1.167 µm to 0.744 µm with increased heating rate from 10ºC/min. to 50ºC/min which can be explained on the basis of phenomenological kinetic equation for grain growth. Dielectric response also found to influence by heating rate. The CCTO ceramic sintered with 50 ºC/min. exhibited highest dielectric constant (ɛr~3915) with nominal losses (0.10) at room temperature in broad frequency range from 10 2 Hz-10 5 Hz. Cole-Cole plots revealed the change in grain boundary resistivity mainly caused by the oxygen vacancy activities and affected by varying sintering heating rate. An anomaly observed for 50 ºC/min heating rate due to trapping of oxygen at grain boundaries. The remnant polarization and coercive field for CCTO ceramic sintered with 50ºC/min were 0.1 µC /cm 2 and 1.477 kV /cm respectively. Remnant polarization found to decrease while the coercive field increases with increasing heating rate applying these are micro-structural dependent.
M. P. Deshpande; Vivek P. Gujarati; Kiran N. Patel; S.H. Chaki
Abstract
Crystals of Glycine with Sodium Nitrate (GSN) taken in concentration ratio of 1:1 were grown by slow evaporation technique. Solubility of the material was determined in double distilled water at different temperatures. Purity of the grown crystal was checked by CHN and EDAX analysis whereas crystalline ...
Read More
Crystals of Glycine with Sodium Nitrate (GSN) taken in concentration ratio of 1:1 were grown by slow evaporation technique. Solubility of the material was determined in double distilled water at different temperatures. Purity of the grown crystal was checked by CHN and EDAX analysis whereas crystalline nature was confirmed from powder X-ray diffraction pattern. Dielectric study of the sample was carried out between the frequency range 1Hz to 100 KHz. FTIR spectra along with Raman spectra was used to look at the presence of different chemical bonds and groups present. Optical absorption spectra recorded in UV-Vis (250-800 nm) region for the GSN crystal was analyzed to determine the optical energy bandgap of the sample. GSN crystal was thermally investigated between 323-773 K at three different heating rates (5, 10, 15 K/min) and activation energy was computed using Kissinger method.
Rohan Dasa; Kaushik Guptaa; Kuntal Janaa; Arabinda Nayakb; Uday Chand Ghosha
Abstract
Strontium-zirconium bimetal oxide (SrZrO3) samples at nanophase were prepared by chemical precipitation-annealnation method, and characterized by powder X-ray diffraction (XRD), UV-Vis and FTIR spectroscopies and field emission scanning electron microscopy (FESEM). Grain size (nm) of the SrZrO3 samples ...
Read More
Strontium-zirconium bimetal oxide (SrZrO3) samples at nanophase were prepared by chemical precipitation-annealnation method, and characterized by powder X-ray diffraction (XRD), UV-Vis and FTIR spectroscopies and field emission scanning electron microscopy (FESEM). Grain size (nm) of the SrZrO3 samples prepared by annealing at 650°C (S650), 850°C (S850) and 1050°C (S1050), respectively, were 55-60, 45-47 and 25-32. The optical band gaps (eV) estimated are to be 4.71 and 4.83 of S850 and S1050, respectively. Both FTIR and XRD studies confirmed the formation of SrZrO3 phase. FESEM images of the S850 sample showed the presence of agglomerated nano spheres with irregular surface morphology. Temperature dependent ac-conductivity analyses of S850 sample showed semiconducting behavior with low thermal activation energy (28 meV). Hopping conduction of charge carriers had been concluded considering the relaxation processes associated with the grain and grain boundaries of the sample. Dielectric behavior of S850 sample was confirmed from considerably high dielectric constant value (~ 140) and low dielectric loss (~ 0.6) at 100 Hz. Cyclic voltammograms suggested the pseudo-capacitive behavior of as-prepared S850 and S1050 samples. Thus as-prepared SrZrO3 nanophase could be used as High-K dielectric material in various applications.
Rajababu Chintaparty; N. Ramamanohar Reddy
Abstract
Zirconium Oxide (zirconia) particles were prepared through hydrothermal technique by using zirconium oxychloride (ZrOCl2.8H2O) and zirconyl nitrate (ZrO (NO3)2.H2O) as precursors. The structural characterization as prepared samples were confirmed by X-ray powder diffraction (XRD) and showed monoclinic ...
Read More
Zirconium Oxide (zirconia) particles were prepared through hydrothermal technique by using zirconium oxychloride (ZrOCl2.8H2O) and zirconyl nitrate (ZrO (NO3)2.H2O) as precursors. The structural characterization as prepared samples were confirmed by X-ray powder diffraction (XRD) and showed monoclinic phase. Further, surface morphology of synthesized zirconia particles were confirmed by scanning electron microscopy (SEM). The energy band gap of synthesized samples was evaluated from UV-vis absorption spectra. The frequency dependence of dielectric constant and dielectric loss of the samples were investigated at room temperature. Zirconium oxychloride was found to be better precursor for obtaining ZrO2 with a higher dielectric constant than Zirconyl nitrate under the same synthesis conditions.
Shweta Thakur; Seema Sharma;Ashutosh Tiwari; Radheshyam Rai
Abstract
Polycrystalline samples of (K0.45Na0.45Li0.1NbO3)1-x-(Ba0.96La0.04Ti0.815Mn0.0025 Nb0.0025Zr0.18 O3)x ceramics (where x = 0.1, 0.3, 0.5, 0.7 and 0.9) were prepared by using a high temperature solid state reaction technique. The XRD patterns of the BLTMNZ doped KNLN at room temperature with x = 0.7 have ...
Read More
Polycrystalline samples of (K0.45Na0.45Li0.1NbO3)1-x-(Ba0.96La0.04Ti0.815Mn0.0025 Nb0.0025Zr0.18 O3)x ceramics (where x = 0.1, 0.3, 0.5, 0.7 and 0.9) were prepared by using a high temperature solid state reaction technique. The XRD patterns of the BLTMNZ doped KNLN at room temperature with x = 0.7 have pure pervoskite phase with tetragonal structure at room temperature and have maximum value of dielectric constant at x = 0.9. Detailed studies of dielectric and impedance properties of the materials in a wide range of frequency (100Hz–1MHz) and temperatures (30 – 500 o C) showed that properties are strongly temperature and frequency dependent. The plots of Zʹʹ and Mʹʹ versus frequency at various temperatures show peaks in the higher temperature range (>300 o C). The compounds show dielectric relaxation, which is found to be of non-Debye type and the relaxation frequency shifted to higher side with increase in temperature. The Nyquist plot and conductivity studies showed the NTCR character of samples.
Manjusha and K. L. Yadav; Manjusha;K. L. Yadav
Abstract
Mixed spinel -perovskite composites of (x) Co0.5Ni0.5Fe2O4-(1−x) Bi0.9La0.1FeO3(x = 0, 0.25, 0.40, 0.55, 1.0) have been synthesized by conventional solid state reaction method and annealed at 850 ºC. The X-ray diffraction (XRD) pattern shows that the composites consisted of spinel Co0.5Ni0.5Fe2O4 ...
Read More
Mixed spinel -perovskite composites of (x) Co0.5Ni0.5Fe2O4-(1−x) Bi0.9La0.1FeO3(x = 0, 0.25, 0.40, 0.55, 1.0) have been synthesized by conventional solid state reaction method and annealed at 850 ºC. The X-ray diffraction (XRD) pattern shows that the composites consisted of spinel Co0.5Ni0.5Fe2O4 and rhombohedral perovskite Bi0.9La0.1FeO3 ceramics. FESEM micrographs show closely packed microstructure with grain size in the range 503 nm - 960 nm. Variation of dielectric constant and dielectric loss with temperature at two fixed frequencies (500 kHz and 1 MHz) was studied. The composite with composition x = 0.55/sintered at 850 ºC exhibits the largest coercitivity (Hc) of 883 Oe. The saturation magnetization (Ms) and magnetic moment (µB) increase with an increase of Co0.5Ni0.5Fe2O4 concentration in the composites. From ferroelectric hysteresis loop analysis the values of remnant polarization (Pr) and coercive field (Ec) was found to lie in the range of 0.018-0.745 µC/cm 2 and 3.89-6.06 kV/cm. The relative change of magnetocapacitance was found to be 6.6% at a magnetic field of 8 kOe for x = 0.55 composition. Impedance analysis suggests the presence of a temperature dependent electrical relaxation in the material having a typical negative temperature coefficient of the resistance (NTCR) behavior analogous to a semiconductor.
Venkata Ramana Mudinepalli; N. Ramamanohar Reddy; Wen-Chin Lin; K.V. Siva Kumar; B.S. Murty
Abstract
This work focuses on the high temperature dielectric and mechanical spectroscopic properties of lead free relaxor Sodium Bismuth Titanate (NBT) ceramics, fabricated by conventional ceramic double sintering method. Systematic measurements of dielectric and mechanical properties have been performed as ...
Read More
This work focuses on the high temperature dielectric and mechanical spectroscopic properties of lead free relaxor Sodium Bismuth Titanate (NBT) ceramics, fabricated by conventional ceramic double sintering method. Systematic measurements of dielectric and mechanical properties have been performed as a function of temperature. A sequence of phase transitions has been studied by both dielectric and anelastic measurements. Three internal friction peaks were observed near 350, 200 and 120 °C. The 350 °C-peak corresponds to a transition associated with the tetragonal (P < /em>4bm) to rhombohedral (R3c) phase, and the 200 °C-peak is related to the ferroelectric to antiferroelectric phase transition. The 120 °C-peak could be ascribed to the interaction between the domain walls and the diffusion of oxygen vacancies in the domains.
Wang Shoude; Lu Lingchao; Cheng Xin
Abstract
Small size particle of ultra-fine fly ash was contributed to the dispersion of carbon fiber in composite in the preparation process. The dispersibility of carbon fiber in composite was associated with self-sensing property of composite. The effect of ultra-fine fly ash on the change in relative dielectric ...
Read More
Small size particle of ultra-fine fly ash was contributed to the dispersion of carbon fiber in composite in the preparation process. The dispersibility of carbon fiber in composite was associated with self-sensing property of composite. The effect of ultra-fine fly ash on the change in relative dielectric constant of carbon fiber sulphoaluminate cement composite under stress was investigated. The sensitivity, accuracy and reversibility of the change in relative dielectric constant under stress have been improved when 10% content (by mass of cement) of ultra-fine fly ash was added into carbon fiber sulphoaluminate cement composite (CFSC). Besides promoting micro capacitor creation, ultra-fine fly ash could endow CFSC with excellent mechanical property and weaken the ions polarization effect. The combination of above three effects upgraded the dielectric behavior of CFSC under stress.
)
)