New medium-temperature proton electrolytes based on CsH2PO4 and silicophosphate matrices

Silicophosphate gels ranging widely in P₂O₅ content and specific surface area have been synthesized by a sol-gel process. We have demonstrated the possibility of producing medium-temperature high-conductivity systems based on silicophosphate matrices and CsH₂PO₄. The thermal, structural, and transport properties of composite proton electrolytes have been investigated. The results indicate that the electrical conductivity of the composites based on matrices with Si : P = 1 : 0.5 increases by up to three and half or four orders of magnitude and that their proton conductivity is ～10^?3 to 3 × 10^?2 S/cm at temperatures from 90 to 220°C and a water vapor content of ?0.6–1 mol % in air. The additive suppresses the superionic phase transition of CsH₂PO₄. The increase in conductivity at low contents of the heterogeneous component is due to both CsH₂PO₄ dispersion and the presence of protonated centers on the matrix surface. When the mole fraction of the additive exceeds 0.3, the composites contain CsH₅(PO₄)₂, a compound with a lower thermal stability, which is responsible for their high conductivity in a limited temperature range.     

Synergistic effect of SiO2 on proton conduction and thermal behavior for nanocomposite electrolyte CsH2PO4 fuel cells

Journal of Materials Science: Materials in Electronics - Solid acid composite electrolytes (1?x)CsH2PO4(CDP)/xSiO2 (0?≤?x?≤?0.35) were prepared and...     

DSC and conductivity studies on PVA based proton conducting gel electrolytes

An attempt has been made in the present work to prepare polyvinyl alcohol (PVA) based proton conducting gel electrolytes in ammonium thiocyanate (NH₄SCN) solution and characterize them. DSC studies affirm the formation of gels along with the presence of partial complexes. The cole-cole plots exhibit maximum ionic conductivity (2.58 × 10⁻³ S cm⁻¹) for gel samples containing 6 wt% of PVA. The conductivity of gel electrolytes exhibit liquid like nature at low polymer concentrations while the behaviour is seen to be affected by the formation of PVA-NH₄SCN complexes upon increase in polymer content beyond 5 wt%. Temperature dependence of ionic conductivity exhibits VTF behaviour.     

Effect of ZrO2 on conductivity of PVC-PMMA-LiBF4-DBP polymer electrolytes

The preparation and characterization of composite polymer electrolytes of PVC-PMMA-LiBF₄-DBP for different concentrations of ZrO₂ have been investigated. FTIR studies indicate complex formation between the polymers, salt and plasticizer. The electrical conductivity values measured by a.c. impedance spectroscopy is found to depend upon the ZrO₂ concentration. The temperature dependence of the conductivity of the polymer films seems to obey the VTF relation. The conductivity values are presented and results discussed.     

Studies on transparent and solid proton conductors based on NH4H2PO4 doped poly(vinyl alcohol)

A novel transparent and anhydrous proton conductor, which can be used in solid electrochromic device (ECD), was prepared by mixing poly(vinyl alcohol) (PVA) with ammonium dihydrogen phosphate (NH₄H₂PO₄). X-ray diffraction, differential scanning calorimeter (DSC), and Infrared spectra were used to characterize the structure of PVA/xNH₄H₂PO₄ composite membrane. Proton conductivity of the composite membranes was studied by the complex impedance method. The proton conductivity of the composite membranes increases with increasing temperature and increases with increasing phosphate doping-level at first and then decreases with increasing phosphate content after a certain value of x. The highest proton conductivity is near the area of x = 0.067. The transmittance of the complex membranes always decreases with increasing doping level of phosphate.     

Solid electrolytes based on Na3PO4 doped with S,Se, Mo,W

The cubic form of Na₃PO₄ forms extensive ranges of solid solutions, which are stable from room temperature to the melting point, by the replacement mechanism, Na + P = Y : Y = S, Se, Mo, W. In all four cases, the conductivity increases markedly with increasing Y content and is attributed to the increase in number of mobile sodium ion vacancies. Partial phase diagrams, lattice parameters and conductivity Arrhenius parameters are given for each system     

Synthesis,structural, band gap,and optical properties of Ba3(PO4)2 hierarchical structural materials

Journal of Materials Science: Materials in Electronics - Ba3(PO4)2 structure with Rhombohedral phase was prepared by a facile wet chemical method. In this experiment, NaOH is used as a surfactant...     

Phase Transition Study of Thermal Dependence of Soft Mode Frequency,Dielectric Constant and Dielectric Tangent Loss Properties in CsH2PO4 (CDP) and CsD2PO4 (DCDP) Crystals

Journal of Low Temperature Physics - Modified two-sublattice pseudospin lattice coupled-mode (PLCM) model Hamiltonian by adding third- and fourth-order anharmonic interactions, extra...     

Study of electrical and structural properties of boron doped polysilicon films with a low nitrogen content

In this work we propose, the study of nitrogen doped Silicon films for an application as a poly-Si gate material for metal-oxide-semiconductor devices. Nitrogen doped silicon films have been deposited at amorphous phase by low-pressure chemical vapor deposition (LPCVD) from disilane Si₂H₆ and ammonia NH₃ at low temperature (480^∘C). The films with varied nitrogen contents have been boron implanted, and annealed at several annealing conditions. The influence of the annealing conditions, the nitrogen tenor and the boron dose on the electrical and the structural properties of films are investigated and correlated. Results show that the conductivity is maximal (σ ∼ 10² (Ω ⋅ cm)⁻¹) for higher annealing temperature, a nitrogen content less than 2% and a strong boron dose. These results indicate that under these optimal conditions, although some nitrogen contents is present in the films, these latter have a conducting behavior. The crystallization of films was found to depend principally on the nitrogen tenor. A quasi-totally crystallization was observed for a nitrogen tenor inferior or equal to 2% and for an annealing temperature of 1100^∘C during 120 min. This result is in good agreement with the greatest value of the conductivity obtained under the same conditions.     

Morphology and ionic conductivity of solid polymer electrolytes based on polyurethanes with various topological structures

Polyurethanes with linear, hyperbranched and comb-crosslinked structures were synthesized and were used to prepare solid polymer electrolytes. The polymer electrolytes were characterized by means of Fourier transform Raman spectroscopy, impedance spectroscopy (IS) and atomic force microscopy (AFM). The results showed that salt concentration significantly influences the morphology and conductivity of the three kinds of polyurethane/LiClO₄ system. When the mole ratios of the ether oxygen atom to lithium ion were controlled to be 12, 4 and 4 respectively for linear, hyperbranched and comb cross-linking polyurethane, the electrolytes typically displayed micro-phase separated morphology and the ionic conductivity also reached maxima respectively at 2.2 × 10^–7 S/cm, 2.8 × 10^–6 S/cm and 2.8 × 10^–5 S/cm at room temperature.     

Microstructure, mechanical properties and ionic conductivity of BICUVOX - ZrO2 composite solid electrolytes

The composites of Cu-partially substituted bismuth vanadate (BICUVOX.1) mixed with a small amount of partially stabilized zirconia (3Y-TZP) were prepared to investigate their microstructure, mechanical properties and ionic conductivity. It was found that the addition of 0.5 to 1 wt% 3Y-TZP reduces the grain size to lower than 1 m in diameter, leading to improvements in micro-hardness and toughness by more than 15%. Due to preferential distribution of 3Y-TZP particles along grain boundaries, grain boundary conductivity and total conductivity decreased with increasing 3Y-TZP content at low temperature, but the decrements remained rather modest and, in addition, became less significant at higher temperature to disappear at 700 K and above.     

Electrical properties and thermal expansion of cobalt doped apatite-type lanthanum silicates based electrolytes for IT-SOFC

The thermal expansion and conductivities have been investigated for Co³⁺ doped lanthanum silicates. The apatite-type lanthanum silicates with formula La₁₀Si_6?xCo_xO_27?x/2 (x = 0.2, 0.4, 0.6, 0.8, 1.0, 1.5) were synthesized by sol–gel process. The thermal expansion coefficient (TEC) of La₁₀Si_6?xCo_xO_27?x/2 was improved with increasing cobalt content because of the lower valence and larger radius of Co³⁺ ion compared to Si⁴⁺. Analysis of AC impedance spectroscopy showed that conductivity increased first and then decreased with increasing cobalt content. There is an optimum doping amount of cobalt and La₁₀Si_5.2Co_0.8O_26.6 exhibits the highest conductivity of 3.33 × 10^?2 S/cm at 800 °C. When x ≤ 0.8, the local distortion caused by doping with Co³⁺ can significantly affect the oxygen channels and assist the migration of the interstitial oxide ions, resulting in the improvement of ionic conductivity. However, excess Co³⁺ dopant (0.8 < x ≤ 1.5) reduced the number of interstitial oxide ions and decreased the conductivity.     

Dielectric properties and optical absorption of X-ray irradiated KD2PO4

The effects of X-ray irradiation on the dielectric constant (K) and loss (tan ) in the frequency range 10² to 3 × 10⁵ Hz, temperature range 30 to 105 ° C, and on optical absorption, have been studied. All these parameters are found to be decreased considerably with increasing doses of X-ray irradiation. The effects of irradiation on these parameters for KD₂PO₄ crystals are found to be greater than those of KH₂PO₄.     

Effect of plasticizer and fumed silica on ionic conductivity behaviour of proton conducting polymer electrolytes containing HPF6

The effect of addition of propylene carbonate (PC) and nano-sized fumed silica on the ionic conductivity behaviour of proton conducting polymer electrolytes containing different concentrations of hexafluorophosphoric acid (HPF₆) in polyethylene oxide (PEO) has been studied. The addition of PC results in an increase in ionic conductivity, whereas the addition of nano-sized fumed silica improves mechanical strength of electrolytes along with a small increase in ionic conductivity. It was observed that the simultaneous addition of PC and fumed silica results in electrolytes with optimum value of ionic conductivity and other properties.     

Crystalline perfection and optical properties of rapid grown KH2PO4 crystal with chromate additive

Potassium dihydrogen phosphate (KDP) crystals were grown in the presence of a series of chromate (CrO $_{4}^{2-}$ ) additive concentrations via rapid growth method. CrO $_{4}^{2-}$ made KDP crystals were coloured by yellow-green, suggesting CrO $_{4}^{2-}$ had entered into the crystal lattice. The elemental analysis indicated that Cr element in KDP crystal was at ppm level. High resolution X-ray diffraction data revealed that the crystalline perfection of these as-grown KDP crystals was destroyed after CrO $_{4}^{2-}$ entered into crystal lattice, embedded in the full width at half maximum was broadened and satellite peaks appeared. Additionally, the extinction ratio was decreased with rise of CrO $_{4}^{2-}$ concentration. CrO $_{4}^{2-}$ introduced two absorption peaks centred at 360 and 280 nm and enhanced the intrinsic absorption near 220 nm, which were at the same band positions compared with the CrO $_{4}^{2-}$ or HCrO $_{4}^{-}$ transmittance spectra. Additionally, CrO $_{4}^{2-}$ could increase the size of light scattering, which was attributed to the point defects and microscopic defects by the replacement by CrO $_{4}^{2-}$ at PO $_{4}^{3-}$ position.