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The pyrochlore compositions Gd2–yNdyZr2O7 (y = 0.0, 0.1, 0.4, 0.6, 1.0, 1.4, 1.6, and 2.0) were synthesized, and their ionic conductivity was determined (100 Hz–15 MHz, 622–696 K). The direct-current (dc) conductivity (σdc) varies upon Nd substitution at the Gd site, and a peaking effect in σdc was observed around y = 1.0. This indicates that a significant increase in conductivity can be obtained at moderately high temperatures by suitable doping at the Gd site with isovalent rare-earth ions like Nd. The extent of oxygen ion disorder determined from x-ray diffraction was found to decrease with increasing Nd content. The dc conductivity obeys the Arrhenius relation σdcT = σ0 exp(−E/kBT). The activation energy E and the preexponential factor σ0, which is a measure of the concentration of the mobile species, increase while going from the ordered Nd2Zr2O7 to the least ordered Gd2Zr2O7. These two processes presumably lead to the peaking of σdc at an intermediate Nd content. Our results also suggest that the cooperative motion of mobile ions does not contribute much to the increase in activation energy in this compound.

La2NiMnO6 (LNMO) was prepared by a combustion method followed by heating at high temperature. Subsequently, the preformed LNMO was annealed in air, oxygen, or N2 atmosphere and characterized by powder x-ray diffraction (XRD), neutron diffraction, superconducting quantum interference device magnetometry, and dielectric analysis. Structural studies by XRD and neutron diffraction revealed the coexistence of partially cation disordered monoclinic (31%) and rhombohedral (69%) phases in the sample annealed in air. However, the sample annealed in oxygen shows about 50:50% of monoclinic and rhombohedral phases. Relaxor-like behavior with relative permittivity of the order of 104 was observed in the sample annealed in air, while relative permittivity decreases to about 200 in samples annealed in oxygen atmosphere. The magnetic properties indicate a well-defined ferromagnetic phase in the oxygen-annealed sample compared to a feeble ferromagnetic signature in the air-annealed one. The dielectric and ferromagnetism of LNMO samples have been related to formation and annihilation of oxygen vacancies.

The semiconductor industry and Microelectronics based devices are in urgent need of materials having low dielectric constant (κ). Efforts are being made, world over, to develop low dielectric (say κ < 2.0) materials for microelectronic applications It is thus of interest to develop materials having low dielectric constant (κ). Polyimide is widely used as packaging material in microelectronic devices packaging due to its good thermal and mechanical properties and good adhesion to metal surfaces. However, the dielectric constant of normal PI is high (κ ∼3.4) as per the requirement of advance insulator material and for microelectronics. We have synthesized polyimide- silica composite films and it is shown that such films have much lower dielectric constant as compared to the normal PI films. The above polymer films were prepared by modifying the pristine polymer at the precursor stage of synthesis. We report the results of FTIR, XRD and dielectric studies of films which have been prepared using PMDA-ODA (Poly Amic acid in DMAc) as precursor and Tetra Ethoxy Silane (TEOS)/Silicic acid as modifier It is seen that crystallinity and the dielectric of the composite films depend on SiO2 concentration.

Lead free scandium doped barium zirconate titanate (Ba 1−x Sc 2x/3 )(Zr 0.3 Ti 0.7 )O 3 abbreviated as (BScZT) (x = 0.02, 0.04, 0.06, 0.08, 0.10) ceramics were prepared by the conventional solid state reaction route and their structural, microstructural and electrical properties were investigated experimentally. X-ray diffraction and Rietveld refinement analysis are indexed by considering cubic symmetry having space group Pm-3 m. Scandium ion (Sc 3+ ) substitution induced A-site vacancies and distortion in three dimensional cation-oxygen networks leads to disorder in the local symmetry as identified in Raman spectra. The microstructural image shows formation of smaller grains of irregular shape and sizes along with aggregative characteristic with successive increase in Sc concentration. Lorentz type quadratic behavior in dielectric dispersion follows modified Curie–Weiss law and indicates a relaxor behavior with diffuse type of phase transition. A non-Debye type of relaxation behavior is observed in these materials. Variation of relaxation strength and diffuse parameters obey the Vogel–Fulcher relation. The ac conductivity highlights the hopping of bound charge carriers between the localized environment at lower temperature and translation hopping at higher temperature is modeled through universal dielectric response.

Three solid solutions of pyrochlores in the series Nd2-yearsGdyZr2O7 (y = 0.8, 1.0, 1.2) were synthesized by the gel combustion method using citric acid as fuel. This results in a soft agglomerate powder as verified by dynamic light scattering. The single-phase nature of the products has been confirmed by x-ray diffraction. The increase in full width at half-maxima in the Raman spectra with an increase in Gd3+ content indicates that disorder increases with Gd3+ content. The morphology and particle size of the products were investigated by transmission electron microscopy. Scanning electron microscopy study reveals that the sintered pellets have a density higher than 92% of theoretical densities. The total ionic conductivity measurements in the temperature range 375–800 °C show that with the increase of disorder (Gd3+ content) in the system the activation energy of conduction increases from 0.98 to 1.06 eV and the preexponential factor, which is proportional to the number of mobile species, also follow the same trend of increase. The total conductivity measured in reducing atmosphere shows no change in electrical conductivity, which verifies a negligible contribution of electronic contribution in this system.

The pyrochlore compositions Gd 2– y Nd y Zr 2 O 7 ( y = 0.0, 0.1, 0.4, 0.6, 1.0, 1.4, 1.6, and 2.0) were synthesized, and their ionic conductivity was determined (100 Hz–15 MHz, 622–696 K). The direct-current (dc) conductivity ( σ dc ) varies upon Nd substitution at the Gd site, and a peaking effect in σ dc was observed around y = 1.0. This indicates that a significant increase in conductivity can be obtained at moderately high temperatures by suitable doping at the Gd site with isovalent rare-earth ions like Nd. The extent of oxygen ion disorder determined from x-ray diffraction was found to decrease with increasing Nd content. The dc conductivity obeys the Arrhenius relation σ dc T = σ 0 exp(− E / k B T ). The activation energy E and the preexponential factor σ 0 , which is a measure of the concentration of the mobile species, increase while going from the ordered Nd 2 Zr 2 O 7 to the least ordered Gd 2 Zr 2 O 7 . These two processes presumably lead to the peaking of σ dc at an intermediate Nd content. Our results also suggest that the cooperative motion of mobile ions does not contribute much to the increase in activation energy in this compound.

La 2 NiMnO 6 (LNMO) was prepared by a combustion method followed by heating at high temperature. Subsequently, the preformed LNMO was annealed in air, oxygen, or N 2 atmosphere and characterized by powder x-ray diffraction (XRD), neutron diffraction, superconducting quantum interference device magnetometry, and dielectric analysis. Structural studies by XRD and neutron diffraction revealed the coexistence of partially cation disordered monoclinic (31%) and rhombohedral (69%) phases in the sample annealed in air. However, the sample annealed in oxygen shows about 50:50% of monoclinic and rhombohedral phases. Relaxor-like behavior with relative permittivity of the order of 10 4 was observed in the sample annealed in air, while relative permittivity decreases to about 200 in samples annealed in oxygen atmosphere. The magnetic properties indicate a well-defined ferromagnetic phase in the oxygen-annealed sample compared to a feeble ferromagnetic signature in the air-annealed one. The dielectric and ferromagnetism of LNMO samples have been related to formation and annihilation of oxygen vacancies.

Three solid solutions of pyrochlores in the series Nd 2-years Gd y Zr 2 O 7 ( y = 0.8, 1.0, 1.2) were synthesized by the gel combustion method using citric acid as fuel. This results in a soft agglomerate powder as verified by dynamic light scattering. The single-phase nature of the products has been confirmed by x-ray diffraction. The increase in full width at half-maxima in the Raman spectra with an increase in Gd 3+ content indicates that disorder increases with Gd 3+ content. The morphology and particle size of the products were investigated by transmission electron microscopy. Scanning electron microscopy study reveals that the sintered pellets have a density higher than 92% of theoretical densities. The total ionic conductivity measurements in the temperature range 375–800 °C show that with the increase of disorder (Gd 3+ content) in the system the activation energy of conduction increases from 0.98 to 1.06 eV and the preexponential factor, which is proportional to the number of mobile species, also follow the same trend of increase. The total conductivity measured in reducing atmosphere shows no change in electrical conductivity, which verifies a negligible contribution of electronic contribution in this system.

G protein-coupled receptor (GPCR)-mediated increases in intracellular calcium generally lead to constriction of airway smooth muscle. Deshpande et al . find that bitter taste receptors, another class of GPCRs, are also expressed on airway smooth muscle cells and, once activated, induce a localized increase in intracellular calcium. Paradoxically, this induces relaxation of airway smooth muscle cells via activation of BK Ca channels. These ligands also relax airways in a mouse model of asthma, suggesting they can be used in conjunction with β-adrenergic receptor agonists to treat obstructive lung disease. Bitter taste receptors (TAS2Rs) on the tongue probably evolved to evoke signals for avoiding ingestion of plant toxins. We found expression of TAS2Rs on human airway smooth muscle (ASM) and considered these to be avoidance receptors for inhalants that, when activated, lead to ASM contraction and bronchospasm. TAS2R agonists such as saccharin, chloroquine and denatonium evoked increased intracellular calcium ([Ca 2+ ] i ) in ASM in a Gβγ–, phospholipase Cβ (PLCβ)- and inositol trisphosphate (IP 3 ) receptor–dependent manner, which would be expected to evoke contraction. Paradoxically, bitter tastants caused relaxation of isolated ASM and dilation of airways that was threefold greater than that elicited by β-adrenergic receptor agonists. The relaxation induced by TAS2Rs is associated with a localized [Ca 2+ ] i response at the cell membrane, which opens large-conductance Ca 2+ -activated K + (BK Ca ) channels, leading to ASM membrane hyperpolarization. Inhaled bitter tastants decreased airway obstruction in a mouse model of asthma. Given the need for efficacious bronchodilators for treating obstructive lung diseases, this pathway can be exploited for therapy with the thousands of known synthetic and naturally occurring bitter tastants.