Effect of the content of MnO on the electric-dielectric properties of potassium-phosphate glasses (original) (raw)
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Electrical and dielectric analysis of phosphate based glasses doped with alkali oxides
In this work, new phosphate glasses with the molar composition 20.7P 2 O 5 –17.2Nb 2 O 5 –13.8WO 3 –34.5A 2 O– 13.8B 2 O 3 where A = Li, Na and K were prepared using the melt quenching technique. These types of glasses have potential to absorb hydrogen in its structure, which makes them promising materials to be used as electro-lytes in intermediate temperature fuel cells. Additionally, niobium phosphate glasses can also have applications such as glass fibers, optical lenses, hermetic sealing and electrodes. The structure of the obtained samples was analyzed using Differential Thermal Analysis (DTA), X-ray powder diffraction (XRD), and Raman spectroscopy and the morphology by Scanning Electron Microscopy (SEM). The DTA measurements revealed values of glass transition temperature around 415 °C, and the Raman analysis showed that the amount of alkali and niobium oxides included on the studied compositions, successfully disrupted the P–O–P chains characteristic of the phosphate glasses. Dc (σ dc) and ac (σ ac) conductivities and dielectric spectroscopy measurements were performed as function of the temperature (200–370 K) which presented conductivity predominantly ionic (σ electronic /σ ionic of about 10 −4). The dielectric spectroscopy was measured in the frequency range 100–1 MHz.
Thermal, optical and electrical properties of MnO2-doped mixed sodium potassium phosphate glasses
Journal of Thermal Analysis and Calorimetry, 2020
Glasses in the system (1 − x)(0.5NaPO 3-0.5KPO 3)-xMnO 2 , with 0 ≤ x ≤ 50 mol%, have been prepared using a melt-quench route. The glasses exhibit a yellow to dark color with the increase in manganese content owing to the presence of Mn 2+ and Mn 3+ ions in the network. The amorphous state of the glasses is evidenced by the X-ray diffraction. In order to get an insight into the physical and structural aspects of these vitreous materials, we have determined some of their parameters such as density, molar volume and glass transition temperature. From differential thermal analysis scan on heating, we evaluated the glass transition temperature (T g) of each glass, which corresponds to the phase transition temperature from solid to viscous liquid. The density (ρ) as a structural index is found to increase while the corresponding molar volume decreases with MnO 2 content. The structural approach of the studied glasses is evaluated by infrared (IR) and electron paramagnetic resonance (EPR) spectroscopies. IR technique allowed us to identify the coexisting bond vibration modes in the glass network, and it has shown that many structural phosphates units coexist, mainly pyrophosphate and metaphosphate structural groups. EPR experiments have shown the presence of Mn 2+ centers in the glasses. The UV-Visible absorption is utilized to estimate the values of the optical band gap (E g) and Urbach energy (ΔE). The optical band gap energy is determined from both the absorption spectrum fitting (ASF) and Tauc's methods. These optical parameters are composition dependence. The dc conductivity of the glasses is determined in the temperature range from 303 to 473 K. It decreases with increasing manganese content. It is thermally activated and followed an Arrhenius behavior. The crystallization of glasses is realized by submitting them to heat treatments, and the crystallized phases are identified by XRD analysis. The crystallization kinetic was studied under non-isothermal conditions. The activation energy (E c) and the Avrami parameter (n) were determined.
Conductivity and dielectric behaviour of iron sodium phosphate glasses
2001
Glasses of the composition (Na 2 P 2 O 6) 100−x (Fe 2 O 3) x , with x = 5, 10, 20 and 25 mol%, have been prepared. The alternating current conductivity, the dielectric permittivity and the loss were measured in the frequency range 0.12-10 2 kHz and in the temperature range 323-623 K. The results show that the contribution of the electronic conduction to the conductivity decreases with decreasing iron concentration. The electronic conduction is possibly due to hopping of an electron from the lower valance state of Fe 2+ to the higher valance state of Fe 3+ ions. The results of the dielectric permittivity show that no maximum was observed in the temperature and frequency range studied. This absence is an indication of non-ferroelectric behaviour of all the samples. However, the thermal activated relaxation mechanism dominates the observed relaxation behaviour. The distribution of the relaxation processes was also studied, and three processes were adequate to describe the present results.
Structural and electric-dielectric properties of some bismuth -phosphate glasses
Journal of Physics and Chemistry of Solids, 2012
In the present study, glasses with composition XBi 2 O 3 (60 À X)P 2 O 5 20Fe 3 O 4 20Li 2 O (0r X r 15) mol% have been prepared by the conventional melt quenching technique. The IR studies show the presence of FeO 4 , FeO 6 , BiO 6 , PO 3 , PQO and PO 4 structural groups. The hyperfine structure of these glasses is investigated using Mössbauer spectroscopy. ME spectroscopy indicated the presence of two different oxidation states of iron (Fe 2 þ and Fe 3 þ ). The ferrous ions Fe 2 þ occupied tetrahedral coordination states, while the ferric ions Fe 3 þ occupied both tetrahedral and octahedral coordination states. The effect of partial replacement of P 2 O 5 by Bi 2 O 3 on the electric-dielectric properties is studied in more details. It is found that, unmonotonic variation in the s dc , (y D /2), s ac (o), e 1 (o), and e 2 (o), as a function of Bi 2 O 3 contents. Also it is found that, the power law exponent, s, is temperature dependent and the CBH model is the most applicable conduction mechanism in all glass samples. Pseudo Cole-Cole diagram of the investigated glassy samples exhibit similar behavior where all plots show a single semicircle indicating a single relaxation process.
The dielectric properties of TeO 2–P 2O 5 glasses
Materials Chemistry and Physics, 2000
The dielectric constant and the tangent loss were measured for the TeO 2 -P 2 O 5 glass system in the frequency range 0.1-10 kHz at different isotherms. The dielectric constant and the tangent loss decreased with increasing frequency, while both of them increased with increasing temperature. The decrease of the dielectric constant with increasing frequency was attributed at low frequency to the contribution of all the polarizability components, while at higher frequencies the absence of ionic and orientational polarizability components. The increase of the dielectric constant with temperature was due to the combination of electronic, ionic and orientational polarizability components. The decrease of the loss factor with increasing frequency was attributed at low frequency mainly to the migration of ions in addition to the electronic polarization loss, while at high frequency the ion vibrations may be the only source of the dielectric loss. The increase of the loss factor with increasing temperature was attributed to the relaxation loss in addition to the conduction loss which increased more rapidly with temperature.
Ionics, 2008
Sodium phosphate glass undoped and doped with different concentrations of chlorides of iron, manganese, and zinc were prepared by melt quenching. The synthesized glasses were characterized by elemental analysis, X-ray diffraction, infrared (IR) spectroscopy, differential scanning calorimetry, and electrical conductivity studies. The undoped sodium phosphate glass (Na2O–P2O5) has low electrical conductivity σ compared to all doped glasses except for 10% FeCl3-doped samples for which σ is found to be the lowest, and the trend is \sigma \left( {-{\text{ZnCl}}_2 } \right) >\sigma \left( {-{\text{MnCl}}_2 } \right) >\sigma \left( {-{\text{FeCl}}_3 } \right) >\sigma \left( {{\text{Na}}_2 {\text{O}}-{\text{P}}_2 {\text{O}}_5 } \right)$$ The Na2O–P2O5–5% ZnCl2, Na2O–P2O5–5% MnCl2 and Na2O–P2O5–1% FeCl3 glassy systems yielded maximum σ values. These results are explained on the basis of changes in the structure of sodium phosphate glass matrix by the addition of Fe, Mn, and Zn ions based on IR spectra and DSC studies.
Structural and dielectric properties of K2O-TiO2-P2O5 glass and its associated glass-ceramic
Materials Today: Proceedings
20K 2 O-30TiO 2-50P 2 O 5 (KTP) glass was elaborated by conventional quenching method. The density and molar volume values of KTP glass are determined. The structure of the glass was performed by Raman spectroscopy. The results revealed that KTP glass consists mainly of orthophosphate and pyrophosphate units, and the titanium occupies the octahedral sites in the glassy matrix. The controlled crystallization of KTP glass was carried out to develop glass-ceramic (GC-KTP). X-ray diffraction was used to identify the crystallized phases in (GC-KTP). Dielectric and conductivity parameters of the glass-ceramic are determined by impedance spectroscopy in the frequency range of 300 Hz to 1 MHz under various temperatures from 300 to 473 K. The results obtained showed that the dielectric parameters (permittivity and dielectric losses) increase at high-temperature and low-frequency and the conductivity is thermally activated and follows the Arrhenius behavior.
Role of manganese in 20K2O-xMnO-(80-x)P2O5 phosphate glasses and model of structural units
2016
Glasses with composition 20K2O-xMnO-(80-x)P2O5 with 0≤ x ≤30 mol% were prepared by conventional melt quenching technique at 1100°C mixtures of K2CO3, MnCO3 and NH4H2PO4. Their density, molar volume, glass transition temperature and infrared spectroscopy have been investigated. Differential Scanning Calorimetry (DSC) measurements give the variation of glass transition temperature (Tg) from 225°C for x=0 to 440°C for x=30 mol %. The density () measurements increase from 2.28 to 2.89 g.cm -3 . The evolution of infrared spectra with the composition is studied and the oxide forming character is discussed. When manganese oxide is added to potassium phosphate glass, phosphate chains are depolymerized by the incorporation of distorted (4) units through P-O-Mn bonds. it is assumed to be presented as [MnO4/2] 2structural units a corner sharing geometry and the electrical neutrality in the system is achieved by the conversion of [POO3/2] into [PO4/2] + units.
Measurement, 2010
The effects of iron ions on dielectric properties of lithium sodium phosphate glasses were studied by non-usual, fast and non-destructive microwave techniques. The dielectric constant (e 0 ), insertion loss (L) and microwave absorption spectra (microwave response) of the selected glass system xFe 2 O 3 Á(1 À x)(50P 2 O 5 Á25Li 2 OÁ25Na 2 O), being x = 0, 3, 6, . . . , 15 expressed in mol.%, were investigated. The dielectric constant of the samples was investigated at 9.00 GHz using the shorted-line method (SLM) giving the minimum value of e 0 = 2.10 ± 0.02 at room temperature, and increasing further with x, following a given law. It was observed a gradual increasing slope of e in the temperature range of 25 6 t 6 330°C, at the frequency of 9.00 GHz. Insertion loss (measured at 9.00 GHz) and measurements of microwave energy attenuation, at frequencies ranging from 8.00 to 12.00 GHz were also studied as a function of iron content in the glass samples.
Conductivity and dielectric behavior of NaPO3–ZnO–V2O5 glasses
Journal of Alloys and Compounds, 2014
A series of zinc-phosphate glass containing different concentrations of V 2 O 5 ((80Àx) NaPO 3 + 20 ZnO + x V 2 O 5 (x = 0-25 mol%)) was prepared by melt quenching method and analyzed by differential scanning caloremetry (DSC) and impredance spectroscopy. The electrical properties of these samples were measured using ac impedance spectroscopy technique over a frequency range of 10 Hz to 13 MHz at several temperatures in the range of 323-673 K. The ac conductivity, dc conductivity, dielectric constant and loss factors were obtained from these measurements. Constant-phase elements (CPE) are used in equivalent electrical circuits for the fitting of experimental impedance data. The impedance spectra have also indicated that the conduction is predominantly polaronic in nature. The frequency and temperature dependence of the electrical modulis as well as dielectric loss parameters have exhibited a relaxation character attributed to the vanadyl complexes. The relaxation effects have been analyzed by the graphical method. From this analysis, it has been established that there is a spread of relaxation times. The results have been further discussed quantitatively in the light of different valance states of vanadium ions with the aid of the data on spectroscopic properties. The frequency dependence of the electric conductivity was found to follow a simple power law behavior, in accordance with the relation r ac ðxÞ ¼ rð0Þ þ A 1 :x s 1 þ A 2 :x s 2 , where s 1 and s 2 are smaller than 1. The thermal activation energies for the electronic conduction were estimated on the basis of the Arrhenius plots. Ó 2014 Published by Elsevier B.V. 2. Experimental procedure 2.1. Sample preparation The glass systems were prepared using pure reagent grade chemicals, NaH 2 PO 4 , ZnO and V 2 O 5 in appropriate proportions. They results in glasses with molar composition: (40Àx/2) Na 2 O + (40Àx/2) P 2 O 5 + 20 ZnO + x V 2 O 5 (x = 0 mol%, x = 5 mol%, 10 mol%, 15 mol%, 25 mol%). The samples are noted by NZV0, NZV1, NZV2, NZV3 and NZV4 for x = 0-25 mol% V 2 O 5 content, respectively.