K. K. Bamzai

Preparation by chemical co-precipitation, spectral and electrical characteristics of neodymium orthophosphate nanoparticles

Abstract Nanoparticles of neodymium orthophosphate (NdPO4) were prepared through a facile wet co-precipitation technique. The X-ray diffraction (XRD) studies revealed the material belonging to monoclinic monazite phase with crystallite size of 30.8 nm. Scanning electron microscopic studies showed that the material was composed of a large number of agglomerated spherical particles having grain size of 92 nm. Thermogravimetric analysis suggested that the structural phase transition was seen above 800 °C. The spectroscopic investigations were carried out using Fourier transform infrared spectroscopy (FTIR). UV-VIS-NIR absorption spectrophotometer showed various transitions from the ground state 4I9/2 to various excited states within the 4f shell and the optical band gap came out to be 3.3 eV. The dielectric constant (e′), dielectric loss (tan d) and ac conductivity ln(sac) were measured in the frequency range of 5 kHz to 1 MHz and in the temperature range of 40 to 500 °C. The dielectric measurement suggested that there was a shift in the value of transition temperature (Tc), thereby indicating relaxor behaviour of the material. The activation energy value decreased with increase in frequency, thereby suggesting the role of mixed ionic-polaronic conductivity.

Dielectric and A.C Conductivity Behaviour of Flux Grown Nickel Titanate (NiTiO3) Crystal

The present paper deals with systematic study of dielectric characteristics and a.c conductivity of single crystal of NiTiO3 above room temperature. These crystals were prepared by high temperature flux technique. Dielectric constant, tangent loss and conductivity studied on these crystals strongly dependent on temperature and frequency of the applied a.c field, the variation depending on range of temperature and frequency. The appearance of pronounced peak at 773°K in the curve of dielectric constant, loss tangent and conductivity versus temperature indicates ferroelectric phase transition. The increase of conductivity with increase of temperature suggests semiconductor behaviour of this material. The lnσa.c versus temperature plot indicates conduction mechanism to be hopping model. The temperature variation of conductivity confirms to Arrhenius law σ = σ0exp. [−Ea/RT], where E is activation energy per mole required for hopping process and σ0 is free space permittivity. The magnitude of activation energy is found to be greater than 0.2 eV per molecule for this crystal which suggest that conduction mechanism is due to hopping.

Preparation of Cerium Orthophosphate Nanosphere by Coprecipitation Route and Its Structural, Thermal, Optical, and Electrical Characterization

Cerium orthophosphate (CePO4) nanoparticles were synthesized via wet chemical coprecipitation technique using cerium nitrate hexahydrate for Ce3

Preparation, Structural, Electrical, and Ferroelectric Properties of Lead Niobate–Lead Zirconate–Lead Titanate Ternary System

A ternary system of lead niobate–lead zirconate–lead titanate with composition xPN–yPZ–(x-y)PT where and , 0.25, and 0.35 known as PNZT has been prepared by conventional mixed oxide route at a temperature of 1100°C. The formation of the perovskite phase was established by X-ray diffraction analysis. The surface morphology studied by scanning electron microscopy shows the formation of fairly dense grains and elemental composition was confirmed by energy dispersive X-ray analysis. Dielectric properties like dielectric constant and dielectric loss ( and ) indicate poly-dispersive nature of the material. The temperature dependent dielectric constant () curve indicates relaxor behaviour with two dielectric anomalies. The poly-dispersive nature of the material was analysed by Cole-Cole plots. The activation energy follows the Arrhenius law and is found to decrease with increasing frequency for each composition. The frequency dependence of ac conductivity follows the universal power law. The ac conductivity analysis suggests that hopping of charge carriers among the localized sites is responsible for electrical conduction. The ferroelectric studies reveal that these ternary systems are soft ferroelectric.

Synthesis, Characterization, and Thermal Decomposition of Pure and Dysprosium Doped Yttrium Phosphate System

Yttrium phosphate and dysprosium doped yttrium phosphate were synthesized from aqueous solutions using rare earth chloride, phosphoric acid, and traces of ammonium hydroxide. The synthesized material was then characterized for their structural investigations using powder X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) supplemented with energy dispersive X-ray analysis (EDAX). The spectroscopic investigations were carried out using Fourier transform infrared (FTIR) spectroscopy. The thermal stability was studied using differential thermogravimetric analysis (DTA), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) techniques. X-ray diffraction analysis reveals that both yttrium phosphate and dysprosium doped yttrium phosphate belong to tetragonal system with lattice parameter  Å,  Å and  Å,  Å, respectively. The stoichiometry of the grown composition was established by energy dispersive X-ray analysis. The EDAX analysis suggests the presence of water molecules. The presence of water molecules along with orthophosphate group and metallic ion group was confirmed by FTIR analysis. Thermogravimetric analysis suggests that decomposition in case of yttrium phosphate takes place in three different stages and the final product stabilizes after 706°C, whereas in case of dysprosium doped yttrium phosphate the decomposition occurs in two different stages, and the final product stabilizes after 519°C.

Electrical and Magnetic Properties of Some Rare Earth Orthoferrites (RFeO3 where R = Y, Ho, Er) Systems

The electrical and magnetic characteristics of some rare earth orthoferrites (RFeO3, where R = Y, Ho & Er) have been discussed. These two characteristics suggest that such system can be categorized under multiferroic with different Curie and Neel temperature. The electrical characteristics shows relaxation phenomenon with Curie temperature varies with change in frequency. The Curie temperature is in the range of 340–480°C, whereas Neel temperature is about 370°C.

Mechanical Behaviour and Fracture Mechanics of Praseodymium Modified Lead Titanate Ceramics Prepared by Solid-State Reaction Route

The praseodymium modified lead titanate ceramics with composition where = 0.04, 0.06, 0.08, and 0.10 prepared by solid-state reaction technique were subjected to indentation induced hardness testing method. The indentations were induced in the applied load ranging from 0.245 N to 4.90 N. The microhardness varies nonlinearly with load and was best explained by the concept of Newtonian resistance pressure as proposed by Hays and Kendall’s law. Crack propagation, fracture toughness (), brittleness index (), and yield strength () were studied to understand the effect of Pr content on various mechanical parameters. The load independent values were found to increase with the increase in praseodymium content.

Dielectric and Conductivity Studies on Pure and Cadmium Doped Barium Phosphate Crystals

Single crystal barium phosphate and cadmium doped barium phosphate has been grown by a room temperature solution technique. Single crystal x-ray diffraction (XRD) establishes that the grown crystal belongs to the orthorhombic system. The dielectric and a.c conductivity properties were investigated thoroughly with regard to change in temperature and frequency. The variation of the dielectric constant (ϵ/), dielectric loss (tanδ) and a.c conductivity ln(σac) was measured in the frequency range of 5 kHz to 1 MHz and in the temperature range of 40 to 420°C. The increase in the value of ϵ/ is almost linear at low temperature whereas, at high temperature its value increases sharply. However, in barium phosphate crystals, there is a shift in the value of ϵ/ at higher temperature indicating relaxor type behaviour of the material. The dielectric measurements indicate the transition in the material to be a diffuse phase transition, whose nature can be explained by the relation 1/ϵ/ − 1/ϵ/ max = A (T – Tc)γ. The tanδ and ln (σac) shows the temperature as well as frequency dependence. The activation energy at various fixed frequencies is calculated from the slope of the graph between ln (σac) versus 1/T (x 103 K−1).

Structural, spectroscopic and optical properties of pure and gadolinium doped neodymium phosphate nanoparticles prepared using wet chemical route

ABSTRACT Nanoparticles of neodymium phosphate and 5% gadolinium (Gd) doped neodymium phosphate prepared by co-precipitation technique belong to the monoclinic monazite phase with space group P21/n. The average crystallite size calculated using Debye-Scherrer and Williamson Hall method matches very well with grain size observed from scanning electron microscope images and Image J software. FTIR analysis signifies the presence of vibration modes along with the phosphate group and a slight shift in wave number was observed with the substitution of gadolinium into neodymium phosphate. Ultraviolet absorption spectrophotometer show transitions from ground state to various excited state within the 4f shell and the absorption edge shifts towards the lower wavelength side (blue shift) with the addition of dopant. Raman spectrum further confirms the formation of phosphate group with relevant peaks.

Effect of neodymium doping on structural, microscopic and electrical properties of barium phosphate system

Neodymium-doped barium phosphate (NdBP) was prepared as single crystal by room temperature solution technique known as gel encapsulation technique. Single crystal X-ray diffraction shows that the crystal belongs to orthorhombic system. The flower type morphology was observed by scanning electron microscope (SEM) and the stoichiometric composition of the prepared crystal was observed by energy dispersive X-ray analysis (EDAX). The presence of functional group and other groups was studied by Fourier transform infrared spectroscopy (FTIR). The electrical properties of these materials like dielectric constant (e′), dielectric loss (tanδ) and ac conductivity [ln(σac)] was studied at different temperatures ranging from 40°C to 420°C in the frequency range of 5 kHz to 1 MHz. The activation energy values decreases with increase in frequency suggesting that the conduction mechanism is because of hopping of charge carriers.