Abstract: The effect of swift heavy ion (SHI) irradiation on the structural and magnetic properties of thin films of Bi-substituted Co2MnO4 prepared by Pulsed Laser Deposition (PLD) is presented. XRD analysis reveals that the BixCo2-x MnO4 (x = 0.0, 0.1 & 0.3) films grown on amorphous quartz, and crystalline LaAlO3 (LAO) exhibited single phase cubic spinel structure with low strain before and after the irradiation at 200 MeV Ag15+ ions at three fluence values 1 × 1011, 5 × 1011 and 1 × 1012 ions/cm2. DC magnetization hysteresis loop study of the films revealed a ferrimagnetic ordering below the transition temperature ~ 185 K and the saturation magnetization was increased by the irradiation at optimal fluence value 51011 ions/cm2. X-ray Magnetic Circular Dichroism (XMCD) studies showed the antiparallel alignments of Co and Mn magnetic moments.
Abstract: The study of pressure induced structural phase transition of silicon carbide and platinum carbide which crystallize in zinc blende structure (B3), has been carried out using the well described three body interaction potential model (TBIPM). Our present TBIP model consists of long range Coulombic, three body interaction and the short range overlap repulsive forces operative up to next nearest neighbor ions. These materials exhibit a first order phase transition from their ZnS (B3) to NaCl (B1) structure. The phase transition pressure for SiC and PtC are 94.5 GPa and 50GPa respectively.
Abstract: Single phase Ba0.8Pb0.2TiO3 (BPT) with improved dielectric and ferroelectric properties was synthesized by Mechano-Chemical Activation (MCA). It is also interesting to investigate the change in different electrical parameters of the sample synthesized by MCA. In the present work, we are reporting the Complex Impedance spectroscopy (CIS) of BPT ceramics synthesized by MCA. Complex quantities like electric modulus (M*) and impedance (Z*) were calculated from measured dielectric constant (ε) and tanδ measured as a function of frequency (70Hz-1MHz) upto 500oC. To understand the relaxation behavior, real and imaginary parts of M* and Z* were plotted as a function of frequency at different temperatures. Typical Cole-Cole plots of Z′ and Z″ indicate the contribution from both grain and grain boundary to the relaxation mechanism.
Abstract: With the objective of exploring the unknown thermodynamic phase diagram of Bi1-xSrxMnO3 family, we present here an investigation of the temperature-dependent (10K < T < 900K) thermodynamic behavior of Bi1-xSrxMnO3 (x=0.25, 0.30, 0.50). We report here probably for the first time the thermal expansion and specific heat along with other thermal properties of strontium doped perovskite manganite BiMnO3. The specific heat values revealed by using RIM are in closer agreement with the available experimental data for some concentrations (x) of Bi1-xSrxMnO3. In addition, the results on the cohesive energy (f) in orthorhombic perovskite phase, molecular force constant (¦), Reststrahlen frequency (no) and Gruneisen parameter (g) are also presented.
Abstract: Effect of rare earth oxides (Y, Nd, Gd, Ho, Yb, Er, Pr, Dy, La, Ce) on the temperature characteristics of BaTiO3(BT)-Nb2O5-ZnO ceramics was investigated. It was found that, according to the effect on the dielectric constant peaks at 40°C and 127°C of BT ceramics, the doping rare earth oxides can be divided into three categories. The different doping effects of rare earth oxides on the temperature capacitance variation of BT ceramics can be explained by the change of the volume fraction of grain core and grain shell in the core-shell structure. BT ceramics sintered at 1140°C in air have the following properties: ε25°C>3300, tanδ≤1.0%, ρ≥1012 Ω•cm and ΔC/C(-55 to +125°C)≤±10%.
Abstract: (Pb0.97La0.02)(Zr0.92-xSnxTi0.08)O3 (PLZST) ferroelectric ceramics with x=0.40, 0.25, 0.15, respectively, were investigated. It was found that these ceramics with different Zr:Sn ratios were perovskite structure. With increasing of Zr:Sn ratio, the phase-transition electric-field of antiferroelectric to ferroelectric phase increased. when x>0.15,All the samples have double hysteresis loops with antiferroelectric phase characteristics. Yet, when the electric field was removed at lower temperature of -5oC and -20oC, for x=0.25 and 0.40, the electric field induced FE phase can remain metastable FE state. But for x=0.15, the induced FE phase recover to AFE phase even at -20oC. Yet, electric field induced FE phase exist as metastable FE phase. TFE-AFE of the samples was -5oC, -20oC, when x=0.40, x=0.25, respectively. With increasing of Zr:Sn ratio, TFE-AFE increaseddecreased, Tc was hardly changed, but the dielectric constant increased from ~2500 to ~6000, the peak changed sharply, dielectric loss increased continuously with increasing of Zr:Sn ratio.
Abstract: Nanosized zinc oxide/lead titanate (ZnO/PT) ceramic matrix nanocomposites have been studied. Under an appropriate sintering condition, ZnO/PT ceramic nanocomposites were successfully fabricated by a pressureless sintering technique. Thermal expansion and polatization behaviors were determined by using the dilatometer. This technique measures the temperature-dependent of the strain, and the magnitude of polarization can be deduced from the sets of the thermal expansion data. The calculated electric polarization values on the ZnO/PT nanocomposite ceramics show the simple approach to determine the temperature dependence of the polarization below and around the transition temperature. Various aspects on understanding the polarization behavior and other effects in the ferroelectric are discussed.
Abstract: The Charge-discharge Properties of Two Different Non-liner Dielectric Capacitors which Were Made by the La-modified PZST Anti-ferroelectric Ceramics (AFE) Capacitors Were Investigated by Measuring the Hysteresis Loops, None-load Discharge Current-time Curves under Different Charge Voltage, and with 100ohm Discharge Current-time Curve. through Compared these Properties with the Liner Capacitors, it Is Evidence to Summarize the No-liner Properties of the AFE Ceramics. it Was Found that, the AFE Capacitors Imax Is Increasing in No-linear with the Charge Electric Field Increase, but to the Linear Capacitor, the Imax-E Curves is a Beeline. and the AFE Imax-E Curve is Similar to the P-E Curve, and this Paper Explained these.
Abstract: BaxSr1-xTiO3 (x=0.4, 0.5, 0.6) ceramics were fabricated by the conventional solid-state reactions method. The temperature dependences of the dielectric constant and tunability were investigated under high DC electric field. It was found that the change of dielectric constant and tunability under the applied electric field were closely related to ferroelectric phase, phase transition region and paraelectric phase states. The Curie temperature (Tc) was gradually shifted to higher temperature and were broadened and depressed with increasing of DC electric field. The tunability dependence of temperature exhibits different trends in a wide temperature range and reaches a maximum value near the ferroelectric-paraelectric phase transition. These results may be helpful in understanding the mechanism of dielectric response under higher electric field.
Abstract: Barium titanate (BaTiO3 or BT) has become one of the most studied functional materials due to its potential application as multilayer ceramic capacitors, PTC thermistors, electromechanical devices, piezoelectric transducers, actuators, dynamic RAM or logic circuitry as well as a great variety of electro-optical devices. In the present study, high energy ball milling has been used to produce nanocrystalline powders of BT. Two categories of powders having average particle size of 35 nm and 25 nm were prepared by setting the milling speed at 250 rpm and 300 rpm respectively, fixing the milling time at 30 hours. Four ceramic samples, BT35-1350, BT25-1350, BT35-1400 and BT25-1400, were formed by sintering the two types of powders at 1350oC and 1400oC for 3 hours. The ferroelectric and piezoelectric properties of the ceramic samples were studied and found to be dependent on the size of the starting nanopowders. The bulk density and piezoelectric constant (d33) of B25-1350 were found to be less than those of BT35-1350, while the reverse was true in case of BT25-1400 and BT35-1400. Well saturated P-E hysteresis loops were observed for all the ceramics with the size and shape of the loops appearing different for the four samples. For both the pairs of ceramics sintered at 1350oC and 1400oC, the remnant polarization (Pr) decreases with starting particle size, that is, as we go from BT35-1350 to BT25-1350 as well as from BT35-1400 to BT25-1400. However, with decreasing particle size of the starting powders, the coercive field (Ec) increases for the ceramics sintered at 1350oC and decreases for the ceramics sintered at 1400oC. The study reveals the importance of an optimized combination of the size of the starting nanopowders and sintering temperature for obtaining BT ceramics with the desired properties.