Dielectric properties of A- and B-site doped BaTiO(3): Effect of La and Ga

Extremely small amounts of La and Ga doping on the A- and B-site of BaTiO(3), respectively, resulting in a solid solution of the type Ba(1-3x)La(2x)Ti(1-3y)Ga(4y)O(3) have been investigated. The present work dwells on the influence of the individual dopants, namely La and Ga, on the dielectric properties of BaTiO(3). The compositions have been prepared by solid-state reaction. X-ray diffraction (XRD) reveals the presence of tetragonal (P4/mmm) phase. The XRD data has been analyzed using FULLPROF, a Rietveld refinement package. The microstructure have been studied by orientation imaging microscopy (OIM). The compositions have been characterized by dielectric spectroscopy between room temperature and 250 degrees C. Further, the nature of phase transition has been studied using high temperature XRD. The resulting Compounds exhibit high dielectric constant, enhanced diffuseness and low temperature coefficient of capacitance. (C) 200

Diffuse phase transition in the la and ga doped barium titanate

Various approaches have been adopted to modify properties of pure compound for potential options as lead free, high k memory material. In the present study, small amounts of co-doping La and Ga on the A and B site of BaTiO(3) respectively, resulting in a solid solution of the type Ba(1-3x)La(2x)Ti(1-3x)Ga(4x)O(3),03 have been investigated. The compounds have been prepared by conventional solid-state reaction. The X-ray Diffraction (XRD) of calcined powder shows the presence of tetragonal (P4/mmm) phase only. The XRD data has been analyzed using the FULLPROF Rietveld refinement package. The sintered pellets have been characterized by dielectric spectroscopy between room temperature and 200 degrees C. The resulting compounds exhibit a remarkable decrease in Curie temperature as well as a significant enhancement in the dielectric constant. The high temperature x-ray diffraction (HTXRD) of few compositions having higher diffuseness have been performed. The tetragonal phase persists over a wide range of temperature, and tetragonality decreases steadily with increase in temperature. which corroborates with the observed diffuse phase transition

Diffuse phase transition in La and Ga doped barium titanate

Phase transitions in BaTiO3 and Ba1-xLaxTi1-xGaxO3 (Y = 0.008, 0.012, 0.016 and 0.02) have been studied by high temperature X-ray diffraction (HTXRD) and Raman spectroscopy. All the compositions in these systems exhibit a single phase. The HTXRD and Raman spectra have been recorded between room temperature and 250 degrees C. The XRD data has been analyzed using the FULLPROF Rietveld refinement package. In compositions with higher diffuseness, the tetragonal phase exists well above the transition temperature (T-max) observed in the dielectric constant vs temperature plot. Unlike pure BaTiO3 where Tmax is accompanied by a crystallographic transition, Bat(1-x)La(x)Ti(1-x)Ga(x)O(3) systems do not exhibit any crystallographic transitions at Tmax. The difference between the T-max and crystallographic transition temperature is proportional to the extent of diffuseness of the transition. (C) 200

Dielectric properties of A- and B-site-doped BaTiO3(I): La- and Al-doped solid solutions

Extremely small amounts of La and Al doping on the A and B site of BaTiO3, respectively, resulting in a solid solution of the type Ba1-3xLa2xTi1-3xAl4xO3 have been investigated. The compositions have been prepared by the Pechini process. The x-ray diffraction (XRD) reveals the presence of tetragonal (P4/mmm) phase. The XRD data has been analyzed using FULLPROF, a Rietveld refinement package. The compositions have been characterized by dielectric spectroscopy between room temperature and 200 degrees C. The resulting compounds (0 <= x <= 0.008) exhibit a remarkable decrease in the Curie temperature as well as a significant enhancement of the dielectric constant. (C) 200

Role of the salt phase in GDC and alumina-based composites

In ceria-salt composite systems, the reasons for a two-order enhancement in conductivity relative to that for doped ceria are still unclear. In our attempt to gain further insight in the phenomenon of conduction, we have investigated two different sets of composites: alumina-salt and ceria-salt. Various compositions in the two-phase composite system involving gadolinium-doped ceria (GDC) and alkali carbonates were prepared and characterized. Later, GDC was replaced with alumina, and similar compositions were prepared and characterized to examine the contribution of the GDC phase to the overall conductivity. The conductivity curves, in spite of variations in composition, exhibited a transition at about 500A degrees C, which also corresponds to the melting temperature of the salt phase. From an analysis of the conductivity data, it is observed that at high temperatures, the salt phase plays a significant role in the conduction enhancement. However, at lower temperatures, GDC primarily appears to contribute significantly to the conductivity

Acoustical study of substituted azoles in N, N -dimethylformamide at different temperatures

1183-1185Ultrasonic velocity and density measurements of 2-(5-amino-[1,3,4]thiadiazol-2-yl)-phenol) (L1), 2-(5-mercapto-[1,3,4] oxadiazol-2-yl)-phenol) (L2), 2-(5-mercapto-[1,3,4]thiadiazol-2-yl)-phenol) (L3), 2-[1-(H-benzimidazol-2-yl]-5-phenyl-1Hpyrazol-3-yl]-4-methyl phenol (L4) and 3-(2-hydroxy-5-methylphenyl- pyrazol-1-yl]-pyridin-4-yl-methanone (L5) in N, Ndimethylformamide (DMF) have been carried out at 303, 308, 313,318 and 323 K in the solute concentration of 1×10-2 moldm-3.The experimental data have been used to calculate various acoustical parameters such as apparent molal volume (ϕv), apparent molal compressibility (ϕk(s)), intermolecular free length (Lf), specific acoustic impedance (Zs) and relative association (RA). The results suggest the presence of molecular interactions. The effect of temperature variation on the strength of molecular interactions has been studied and the data have been quantitatively explained in terms of solute-solute and solute-solvent interactions

Ultrasonic behaviour and study of molecular interactions of substituted azole in N,N-dimethylformamide at different temperatures and concentrations

2102-2104Ultrasonic velocity and density measurements of 2-(4-amino-5-mercapto-[1,2,4) triazol-3-yl )-phenol [AMTP) in N, N-dimethylformamide(DMF) have been carried out at 303, 308, 313 and 318 K in the concentration range 2-10×10-3 mol dm-3. Different acoustic properties like apparent molal volume, apparent molal compressibility, intermolecular free length, specific acoustic impedance and relative association have been determined. The results of the present study suggest the presence of molecular interactions in DMF. These parameters have been interpreted in terms of solute-solvent and solute-solute interactions

Magnetoelectric properties of microwave sintered BiFeO3 and Bi0.90La0.10Fe0.95Mn0.05O3 nanoceramics

Multiferroic materials have attracted the attention of scientific community all over the world due to smart functionality and attractive applications such as in magnetoelectric memory and magnetoelectric sensors. In this paper, we report on the ferroelectric, magnetic and magnetoelectric properties of microwave sintered BiFeO3 (BFO) and Bi0.90La0.10Fe0.95Mn0.05O3 (BLFMO) ceramics. The ferromagnetic and paramagnetic components have been deconvoluted using standard magnetization equation. The ferromagnetic saturation and paramagnetic susceptibility for BFO are found to be 0.046 emu/g and 1.17 x 10(-5) emu/g.Oe respectively. The magnetization in BLFMO increases enormously as compared to BFO due to suppression of cycloid spin. The magnetoelectric voltage coefficient for BFO is 3.37 mV/cm.Oe, while for BLFMO it is 10.11 mV/cm.Oe. As compared to BFO, BLFMO exhibits improved ferroelectric, magnetic and magnetoelectric properties. (C) 2017 Elsevier B.V. All rights reserved

Effect of substrate temperature on the structural and electrical properties of La and Mn co-doped BiFeO3 thin films

The effect of substrate temperature on the structural and electrical properties of multiferroic Bi0.90La0.10Fe0.95Mn0.05O3 (BLFMO) thin films deposited on Pt (111)/Ti/SiO2/Si substrate using pulsed laser deposition (PLD) has been investigated. Films with substrate temperature ranging from 450 degrees C to 650 degrees C have been deposited. The grain size and roughness are found to increase with substrate temperature. The film deposited at 575 degrees C exhibitsmaximumremnant polarization around 39 mu C/cm(2) and a coercive field of 400 kV/cm. The cyclic fatigue study of the sample shows only 4% loss after 10(8) cycles. Complex impedance study of the BLFMO thin films demonstrates electrical homogeneity of the sample. AC conductivity data has been fitted using Jonscher single power law, and value of n found to be <1 indicating translational hopping conduction mechanism. The lowest leakage current found is 4.37 x 10(-6) A/cm(2) at 575 degrees C. The leakage current mechanism is found to be dominated by space charge limited current and Fowler-Nordheim conduction mechanism. (C) 2016 Elsevier B.V. All rights reserved

H2S sensing properties of La-doped nanocrystalline In2O3

The nanocrystalline powders of pure and La3(+)-doped In2O3 with cubic structure were prepared by a simple hydrothermal decomposition route. The structure and crystal phase of the powders were characterized by X-ray diffraction (XRD) and microstructure by transmission electron microscopy (TEM). All the compositions exhibited a single phase, suggesting a formation of solid solution in the concentration of doping investigated. Gas-sensing properties of the sensor elements were tested by mixing a gas in air at static state, as a function of concentration of dopant, operating temperature and concentrations of the test gases. The pure In2O3 exhibited high response towards H2S gas at an operating temperature 3, 3, 150 degrees C. Doping of In2O3 with La increases its response towards H2S and La3+ (5.0 wt.% La2O3)-doped In2O3 showed the maximum response at 125 degrees C. The selectivity of the sensor elements for H2S against different reducing gases was studied. The results on response and recovery time were also discussed. (C) 200