Effect of SrO on the Structure of Apatite and Wollastonite Phases of Na₂O-CaO-SiO₂-P₂O₅Glass System

Glasses in the system 24.5Na2O·24.5CaO·6P2O5·xSrO·(45-x)SiO2 have been studied in the composition region of x = 0 - 15 mol%. The as prepared glasses are transparent and have an amorphous network structure. On the otherhand, heat treated glasses are transformed to opaque white glass ceramic characterized by their highly crystalline network structure. Crystalline apatite (calcium phosphate, Ca3(PO4)2, wollastonite (calcium silicate, CaSiO3), and strontium calcium phosphate Ca2Sr(PO4)2 are the main well-formed crystalline species played the major role in material bioactivity. Increasing SrO leads to enhancing material crystallite and enhances the hardness of the host glass matrix. The change of XRD spectra, 31P NMR chemical shift and hardness number upon increasing SrO are considered due to modification of the apatit Ca(PO3)2 to involve Sr ions inducing Ca2Sr (PO4)2 apatite one. Such species play the role in enhancing material properties and hardness.

Assembly of functional carboxymethyl cellulose/polyethylene oxide/anatase TiO_(2) nanocomposites and tuning the dielectric relaxation, optical, and photoluminescence performances

Nanocomposite films consisting of carboxymethyl cellulose,polyethylene oxide(CMC/PEO),and anatase titanium diox-ide(TO)were produced by the use of sol-gel and solution casting techniques.TiO2 nanocrystals were effectively incorporated into CMC/PEO polymers,as shown by X-ray diffraction(XRD)and attenuated total reflectance fourier transform infrared(ATR-FTIR)analysis.The roughness growth is at high levels of TO nanocrystals(TO NCs),which means increasing active sites and defects in CMC/PEO.In differential scanning calorimetry(DSC)thermograms,the change in glass transition temperature(Tg)val-ues verifies that the polymer blend interacts with TO NCs.The increment proportions of TO NCs have a notable impact on the dielectric performances of the nanocomposites,as observed.The electrical properties of the CMC/PEO/TO nanocomposite undergo significant changes.The nanocomposite films exhibit a red alteration in the absorption edge as the concentration of TO NCs increases in the polymer blend.The decline in the energy gap is readily apparent as the weight percentage of TO NCs increases.The photoluminescence(PL)emission spectra indicate that the sites of the luminescence peak maximums show slight variation;peaks get wider,while their intensities decrease dramatically as the concentration of TO increases.These nanocomposite materials show potential for multifunctional applications including optoelectronics,antireflection coatings,pho-tocatalysis,light emitting diodes,and solid polymer electrolytes.

Structural and dielectric properties of prepared PbS and PbTe nanomaterials

In this work, PbS and PbTe nanomaterials with various morphologies were synthesized by a hydrothermal method. The structural properties were investigated by using X-ray diffraction(XRD) and corresponding scanning electron microscopy together with their EDX analysis. Both the PbS and PbTe nanomaterials possess good polycrystalline structure. The crystallite size, determined from the XRD data, of PbS is 5 nm whereas the corresponding value of PbTe is 2.69 nm. SEM micrographs reveal that the prepared PbS nanomaterial has starshaped structures, micro-flowers, some cubes, and semi-dendrites, whereas PbTe has semi-flower structures. Additionally, the dielectric properties have been studied in a broad frequency range from 0.1 Hz up to 1 MHz at temperatures from 298-423 K. The real and imaginary parts of the complex dielectric constant ε' and ε" of PbTe are comparatively higher than those of PbS. Moreover, the dielectric data were analyzed on the basis of the electric modulus.

Structural and AC electrical properties study of solid metal urea complexes

The complexation of solid urea with(Co^(2+)),(Cu^(2+))or(Ni^(2+))ions has been studied by using dielectric spectroscopy technique over a wide frequency range at different temper atures.Samples'structure were investigated by XRD,FTIR and FT-Raman spectroscopy.FIIR and Raman analy sis indicated that the urea coordinates with the metal atoms through the same oxygen-metal bond(O-M).Furthermore,XRD analysis showed that the samples have polycrystalline structure with single phase.The pemittivity of complexes was found at much higher values than that of the ligand(pure urea),showing structure dependency.Furthermore,two relaxation peaks were observed in the dielectric loss spectra corresponding to the orientation po larization of urea molecule,and some parts of urea molecule may be NH2 groups.Both relaxation peaks correspond to thermally activated because they were shifted to higher frequency with the temperature increase.The peak position for the low frequency relaxation peak was observed lht the same relaxation time(τ=7.6× 10^(-4) s),corresponding to the coordination mode through the same O-M bond.Novelty of this work is the successful finding of the relationship between the crystalline phase,coordination mode and the dy namic molecular behavior of solid urea and its complexes using the dielectric spec-troscopy techn ique.

Doping effect of SrZrO_(3) on KNLN ceramics structure and their dielectric properties

In this work,lead-free systems;(1-x)(K_(0.465)Na_(0.465)Li_(0.07))NbO_(3)–xSrZrO_(3)(x=0,0.005,0.050,0.095 and 0.14)were synthesized by the conventional solid-state reaction technique.XRD,SEM,densification parameter as well as dielectric parameters of the obtained KNLN ceramics were investigated.XRD analysis showed the formation of orthorhombic perovskite structure in all investigated specimens.SrZrO_(3)(SZ)inhibited the grain growth and increased the distribution of grains uniformly in the microstructure.In addition,SZ changed the crystalline system of KNLN ceramics abnormally.As a consequence,the permittivity,dielectric loss as well as AC conductivity decreased remarkably.The ceramics of x=0.005 are characterized by low conductivity(10-10 S/cm),low dielectric loss(0.005)and relatively high permittivity(34).They can be useful for the electrical capacitors fabrication and filtering out noise from signals in resonant circuits.At frequencies lower than 105 Hz,DC conductivity and separation of the charges at the interfaces were found to dominate the electrical behavior of ceramics,whereas at higher frequencies,a faster or dipole polarization may become more dominated.A broad peak has been observed in the imaginary part of electric modulus revealing to the non-Debye dielectric relaxation behavior.Quantum mechanical tunneling(QMT)was found to be the most suitable to characterize the electrical conduction mechanism in the ceramic compounds.

Effect of sulfur doping on the dielectric properties of Sb_(2)Se_(3) system

In this paper,we report the effect of sulfur doping on the electrical and dielectric properties of semiconducting Sb_(2)Se_(2)S over wide ranges of temperatures(298–473 K)and frequencies(42–10^(6) Hz).Sb_(2)Se_(2)S system has been prepared by the direct fusion and cooling cycle of a mixture of the constituent elements,in stoichiometric ratio and purity 99.999%,in vacuum-sealed silica tubes.X-ray analysis showed a decrease in the cell parameters a,b and c upon doping with sulfur.However,the pure and doped Sb_(2)Se_(3) showed the single orthorhombic phase structure.The permittivity of Sb_(2)Se_(2)S showed a decrease with increasing frequency due to a decrease in the average bond strength.While,ac conductivity increased with the frequency increase,obeying the Jonscher’s universal dynamic law.The conductivity temperature dependence is well described by the correlated barrier hopping model.The activation energy calculated from DC conductivity is found at higher value(0.79 eV)as compared to that reported in the literature for other antimony selenide compounds.Accordingly,a new Sb_(2)Se_(2)S compound is suggested which may be useful for electronic devices.