Copper Phosphate Glasses Research Articles

The effects of the incorporation of lutetium oxide on the density and optical properties of copper phosphate glasses

A range of phosphate glasses containing lutetium was prepared by the melt quenching technique. The densities of annealed and unannealed glass samples, molar volumes and the optical energy gapE opt of thin blown films of the glasses were determined. It was found that the density and molar volume both increased with increase of Lu2O3 content. TheE opt values showed that they are not sensitive to the incorporation of small amounts of oxides.

Electrical conductivity of copper phosphate glasses containing lutetium

Etude des conductivites electriques de verres des systemes binaire P 2 O 5 -CuO et ternaire P 2 O 5 -CuO-Lu 2 O 3 a des temperatures comprises entre 293 et 573 K

An electron spin resonance study of copper phosphate glasses containing some rare earth oxides

The electron spin resonance spectra of phosphate glasses containing mixed Cu2+-Er3+ and Cu2+-Lu3+ oxides have been examined. A reduction in the copper (II) signal intensity in the glasses as the proportion of rare earth oxide is raised corresponds to an increase in the reduced valency ratio C in the glasses. Differences between the behaviour of glasses containing erbium and those containing lutetium are observed and probably arise from magnetic coupling between copper (II) and erbium (III).

Direct and alternating electrical conduction in copper phosphate glasses containing praseodymium and calcium

Glasses of various compositions were prepared and included Pr6O11-CuO-P2O5 and Pr6O11-CaO-CuO-P2O5. The direct electrical conduction mechanism was generally discussed in terms of small polarons for the whole series of glasses. Alternating electrical conduction was discussed according to the Elliott model and the Meyer-Neldel rule.

Optical properties of some copper phosphate glasses containing calcium and barium

In many amorphous semiconductors and dielectrics the variation of the absorption coefficient ~(co) with photon energy shows three regions. The first is the region of very high absorption. The second extends over several orders of magnitude of ~(co) and the third is described as a weak absorption tail. For the higher values of the absorption coefficient at the absorption edge the form of ~(~) with photon energy was given in quadratic form by Tauc et al. [1] and discussed in more general terms by Davis and Mott [2], whose equation was of the form 0~(0.)) = B(ho) -- eopt)n/h(D (1) where B is a constant, Eopt is the optical gap and n is an index which usually has the value 2 for amorphous materials, this being the value appropriate to absorption by indirect transitions in k-space. According to the above expression Eovt has the value h~o when the quantity (~hco) 1/2 = 0. The third region of the absorption edge at lower values of ~(~) is often described by a relationship developed by Urbach [3]. He assumed that in this region the absorption coefficient was an exponential function of the photon energy h(co) and therefore c¢(oJ) = ~0 exp (hco/AE) where c(0 is a constant and AE is the width of the tail of the localized states. The optical absorption coefficient c((~o) is given by the equation ~(~o) = (l/d) In (Io/It), where d is the thickness of the sample and In Io/It is the absorbance. Here I0 and It are the intensities of the incident and transmitted ultraviolet beams, respectively. Alkaline earth metals like calcium and barium act as network modifiers in glass in a similar way to alkali metals such as sodium. TABLE I Chemicai composition of the glasses (original composition) Glass P205 content CuO content CaO content BaO content sample (mol %) (tool %) (mol %) (mol %) l 65 35 2c

Electrical conductivity of copper phosphate glasses containing calcium and barium

Electrical conductivity of copper phosphate glasses containing calcium and barium

A study of electron spin resonance of copper phosphate glasses containing tellurium oxide

Electron paramagnetic resonance in glasses of compositions (P2O5)100−x-(CuO)x and (P2O5)50-(TeO2)50−x-(CuO)x where x varied from 20 to 40 mol% has been investigated. The distribution of the copper between the two main valency states is determined from measurements of e.s.r. arising from the Cu2+ centres. The study of e.s.r. enables the distribution of copper in the glasses between the different valency states to be determined and thus indirectly provides evidence for hopping conduction in the glasses. From the results of e.s.r. and the chemical analysis of the samples it is found that the reduced valency ratioC, i.e. the ratio of the concentration of Cu+ ions to that of total copper in the glass, increases with increasing CuO content.

A study of electron spin resonance in copper-phosphate glasses containing praseodymium

The e.s.r. spectra of glasses of compositions (P2O8)65(CuO)35−x(Pr6O11) and (P2O5)65(CuO)25-(CaO)10−x(Pr6O11) x , wherex varied from 0 to 5 mol %, were measured. From the results and the chemical analyses of the samples it is found that the reduced valency ratioC of the copper in the glasses investigated generally increases with increasing Pr6O11 content. In our samples it is believed that enhanced chemical reduction of the cupric (Cu2+) ion is a consequence of its interaction with a reduced ion of the added praseodymium oxide.

AC conductivity of copper phosphate glasses

The ac conductivity of σac copper phosphate glasses with different compositions is measured in the frequency range 102 to 107 Hz and over the temperature range 300 to 513 K. The observed frequency dependence in the measured range can be expressed as Aωs8 (0.7 < s < 1) up to 1 MHz. At frequencies above 1 MHz the conductivity obeys an equation of the form σ(ω) ∞ ωs where s > 1.0. La conductibilité alternative σac des échantillons de verre de phosphate de cuivre avec compositions différentes est déterminée pour les fréquences entre 102 et 107 Hz et pour les températures entre 300 et 513 K. La dépendance sur la fréquence peut être représentée par l'expression σac = Aωs, 0,7 < s < 1,0 (A est un constant, ω la fréquence radiale et s un index). Pour les fréquences plus hautes que 1 MHz la conductibilité obéit une expression de la mμme forme mais avec 7sigma; > 1,0.

Electrical conduction in copper phosphate glasses containing nickel or cobalt

Electrical conduction in copper phosphate glasses containing nickel or cobalt

Electrical conduction in copper phosphate glasses containing nickel or cobalt

A variation in d.c. conductivity and activation energy of 35 mol%CuO-65mol%P2O5 glasses is observed as CuO is gradually replaced by NiO or CoO. These results are believed to be due to the change in the redox ratio of the two transition metal oxide glasses, which causes an increase and then a decrease of polaron hopping transitions between the ions of the same element and between the ions of the different transition metal elements.

Some studies of the optical properties of copper phosphate glasses containing praseodymium

A range of copper phosphate glasses containing praseodymium was prepared and the optical absorption edges and infrared optical absorption spectra were measured. The optical energy gap of copper phosphate glass doped with praseodymium is slightly higher than the corresponding composition of the base glass. Heat treatment at 400 and 800° C caused some changes in the infrared absorption bands which are related to the characteristics of the Pr6O111 component.

Some studies of the optical properties of copper phosphate glasses containing praseodymium

Some studies of the optical properties of copper phosphate glasses containing praseodymium

Photoconduction behaviour in copper phosphate glasses

Preparation de verres contenant CuO dans differentes conditions de fusion afin d'obtenir des rapports Cu + /Cu eleves et etude des photoreponses possibles. La composition totale P 2 O 5 -BaO est choisie comme matrice hote, et ne participe pas au mecanisme electronique

Electrical properties of copper phosphate glasses I. DC electrical behaviour

The ac and dc electrical properties of the P 2O 5BaOCuO glass system have been measured. TSPC and TSDC experiments and dc conductivity as a function of time indicate the predominantly electronic character of these glasses. The conduction process can be basically explained by a polaron hopping model in an adiabatic regime. Conductivity values which depend on the glass microstructure and switching phenomena are observed. The filamentary-feature of this process suggests a Poole-Frenkel mechanism. A Debye dielectric relaxation non-simple process is deduced from the frequency and temperature dependence of loss tangent and dielectric constant. The activation energies agree with those determined from dc measurements, suggesting a unique electronic hopping conduction mechanism in both regimes. The ac and dc electrical properties are strongly affected by the glass composition and essentially by the redox Cu +/Cu t ratio. A conduction model accounting for ac and dc behaviour is finally proposed.

The control of the electrical conductivity of copper phosphate glasses by the admixture of chlorine during preparation

Abstract The electrical conductivity of copper phosphate glasses depends on the relative concentrations of Cu+ and Cu2+ ions and it is found that by adding cupric chlorine to the melt when the glass is formed the added chlorine which acts as an oxidizing agent alters the ratio of the concentration of Cu+ and Cu2+ and thus the conductivity. The change in the concentration of Cu2+ ions in the glasses is determined by infrared spectroscopic measurements and by studies of electron spin resonance, and the change in the Cu+ ion concentration is inferred since the total copper content in the glasses is held constant. It is suggested that the principle of adding a component in the form of a strong oxidizing agent to the glass to alter the reduced valency ion ratio may be of general application in the control of electrical conductivity in transition metal ion glasses.

Bond type, polarisation and electron conduction in some oxide and chalcogenide glasses

Although it is commonly accepted that the mechanism of switching must differ in detail in the numerous systems in which it has now been reported, the close parallelism between the electrical phenomena suggests that a common and fundamental process remains to be found as the prime cause of the various effects.The systems in which bistable (memory) switching occurs, can be divided into two groups; two — or morecomponent metal oxide system, and single or multi-component metal chalcogenide system, and in every case the systems either are glasses or are closely related to known vitreous compositions. It is reasonable to assume that the tendency of a system to form a glass and its ability to show electrical bistable behaviour are intimately related. This paper is an attempt to sketch a framework for such a correlation and to follow through some of the implications.The first part will present a view of the structure of the vitreous state which is to be used in the second part to develop a model of switching covering both oxide and chalcogenide systems, and in the third part some results on the thermoelectric properties of some copper phosphate glasses are reported and their implications considered.