Melt quenched “SnO 2(50-x)PbO:50V 2O 5” glass system containing x = 5, 10, 15 in molar ratio has been investigated. Effects of heating rate, glass transition, crystallization, melting temperature and infrared spectra of SnO 2 substituted PbO-V 2O 5 glass system are reported. XRD results show that perfect vitrification has been achieved for all the glass samples after annealing at 150 °C. DSC results have indicated that eutectic composition of the lead metavanadate has been maintained for all the glass systems up to 15 mole% of substitution. IR spectra for a SnO 2 substitution of 5 mole% V=O stretching frequency occur at 966 cm <sup>-1</sup> without appearance of any additional peak. But for 10 mole% and 15 mole% SnO 2 substituted samples, additional peaks appear at 1023 and 1005 cm<sup> -1</sup> indicating the effect of SnO 2 in the vanadate crystalline matrix such that there is an elongation of V=O bond. Since the crystalline matrix is affected, we can expect similar effect in the glass matrix also.
Transport properties of semiconducting glasses are very interesting and provide useful information on the conduction mechanisms. Modern glasses are of crucial importance for electronics and have been widely used in industry, space explorations, computer memory units, etc. IR spectroscopy is a particularly suitable method for the structural studies of vanadate system in glass and crystalline forms because of the characteristic vanadate group’s vibrational frequencies which can be easily identified. Structural models for PbO-V2O5 glass systems have been discussed on the basis of IR spectroscopy [
The glasses were obtained by melting a chemically pure PbO, V2O5 and SnO2 in amounts varying from 5 to 15 mole% PbO and SnO2 in glazed silica crucibles in the 800˚C - 1200˚C temperature range. Vitrification was achieved by rapid cooling of the melt using a roller technique. The glasses were subjected to crystallization at 380˚C. The prepared samples were grounded into fine powder for X-ray, DSC and FT-IR studies. X-ray studies were carried out on a PAN Alytic X’Pert-PRO diffractrometer using CuKα radiation at 1.5418Å and diffractrometer settings in the 2θ range from 10˚C - 70˚C by changing the 2θ with a step size of 0.020. Differential Scanning calorimetry investigation of glass specimens was performed using DuPont, USA make model 2000 DSC instrument. DSC scans were conducted using 5 - 10 mg ground as-cast glass specimens which heats up at the rate of 10˚C/min between 0˚C and 600˚C in a platinum crucible and alumina powder was used as the reference material. The density of the glass samples was determined by the Archimedes principle, using toluene as immersion liquid. In the present studies IR spectra were recorded for both the vitreous and non-vitreous samples in order to study the effect of a different metal oxide substitution in the place of PbO in the lead metavanadate glass systems.
The X-ray diffractograms annealed at 150˚C containing (x = 5, 10, 15 mole%) of SnO2 showed no trace of crystallinity and are shown in
DSC investigations were conducted on the SnO2-PbO-V2O5 glasses. The DSC patterns for these glass systems shown in
Glass Composition (mole%) | Tg (˚C) | Tc (˚C) | Tm (˚C) | Kg | D (g/cm3) | ||
---|---|---|---|---|---|---|---|
V2O5 Content (mole%) | PbO Content (mole%) | SnO2 Content (mole%) | |||||
50 | 50 | 0 | 241 | 300,412 | 500 | 0.156 | 5.075 |
50 | 45 | 5 | 253 | 292,390 | 496 | 0.099 | 4.928 |
50 | 40 | 10 | 251 | 294,391 | 495 | 0.134 | 5.264 |
50 | 35 | 15 | 248 | 287,385 | 494 | 0.138 | 5.501 |
There is a slight change in Tg along with an increase in the number of crystallization peaks, the Tg values decrease with increasing SnO2 contents, these results suggest that SnO2 acts as a network modifier where as PbO acts as a network former [
Lower Kg suggests higher tendency of crystallization and lower thermal stability. Kg represents the temperature interval during nucleation [
A consequence of disorder in the amorphous or glass systems when compared to crystalline forms is the
Glass Composition (mole%) | ||||
---|---|---|---|---|
State | ѵ (V=O) | ν (VO2) ν (VO3) | ν (VOV) | |
50V2O5:50PbO [ | G C | 968 | 934 892,869,842 | 771 765,723 |
50V2O5:50PbO [ | G C | 964 966 | 885,839 | 770 762,720 |
5SnO2:45PbO:50V2O5 | G C | 912 966 | 873,831 883,837 | 754,717 |
10SnO2:40PbO:50V2O5 | G C | 966,1023 | 802 839,884 | 754,715 |
5SnO2:35PbO:50V2O5 | G C | 941 962,1005 | 875,835 883,837 | 758,715 |
Glass Composition (mole%) | ||||
---|---|---|---|---|
State | CV | (VOV) | δ (VO2, VO3) | |
50V2O5:50PbO [ | G C | 646 666 | 574 | 423 534,489,434 |
50V2O5:50PbO [ | G C | 662 668 | 570 | 539,462,433 532,470,438 |
5SnO2:45PbO:50V2O5 | G C | 667 | 599,532 530 | 478,430 |
10SnO2:40PbO:50V2O5 | G C | 667,626 | 599,522 526 | 478,462,435 478 |
5SnO2:35PbO:50V2O5 | G C | 617 | 545 538 | 484,412 |
υ (V=O) symmetric stretching, υ (VO2) υ (VO3) asymmetric, stretching, υ (VOV) bending frequency (symmetric and antisymmetric), C.V. combination vibration of (VO3)n single chain, G indicates glass.
breakdown of the wave vector selection (k-selection) rules, which allows electromagnetic radiation to couple with vibrations other than k = 0. As a result, unlike the crystalline case in which narrow well defined lines are observed, broad and diffuse bands representing a continuum of IR absorption result. Even though bands due to individual, localized structural units are observable, the identification of IR spectra of glasses alone is rather difficult unless crystalline spectra are also present. Hence the present discussion mainly corresponds to the IR bands observed in the devitrified samples. SnO2 substituted samples for x = 10 and 15 mole% , there is an indication of additional bands at 1023 cm−1 beside 966 cm−1 and 1005 cm−1 beside 962 cm−1 the appearance of additional bands can be understood as the splitting of the original V=O stretching band into affected and unaffected components. The affected components arises due to the effect of dopant i.e. SnO2 in the present case on V=O bond the glass matrix. In this case from the IR spectral evidence we can summarize the following.
As SnO2 is substituted for PbO, SnO2 is replacing PbO in the glass network in such a way that it affects V=O bond frequency, as evident by the shift in V=O band (at 1023 cm−1) whose intensity increases with the increase of SnO2 concentration. The affected V=O band (at 966 cm−1) indicates the presence of meta vanadate phase containing PbO in the usual evidence we can summarize the following. As SnO2 is substituted for PbO, SnO2 is replacing PbO in the glass network in such a way that it affects V=O bond frequency, as evident by the shift in V=O band (at 1023 cm−1) whose intensity increases with the increase of SnO2 concentration. The affected V=O band (at 966 cm−1) indicates the presence of metavanadate phase containing PbO in the usual glass network. The occurrence of the band at 1005 cm−1 is due to the indirect effect of SnO2 on the V=O band in the new stable phase that is being formed. In x(TiO2):(100−x)(V2O5) glass containing x = 20 mole%, Dimitriev et al. [
Perfect vitrification has been achieved for all the glass samples as can be seen from their X-ray diffractograms of the prepared samples after annealing at 150˚C for two hours. DSC recordings show that eutectic composition of the lead metavanadate has been maintained for all the glass systems up to 15 mole% of substitution. The DSC data also indicate that all the glass systems are characterized by more than one crystallization peak. This can be thought as an evidence for the existence of more than one meta-stable phase in the glass systems. The dopant SnO2 is not divalent oxide like PbO. Besides SnO2 is known to be glass former unlike PbO which is replacing PbO in the glass network in such a way that the eutectic composition is maintained. In the present studies the IR spectra of SnO2 substituted samples of 5 mole% V=O stretching frequency occur at 966 cm−1 without the appearance of any additional peak. But for 10 mole% and 15 mole% SnO2 substituted samples, additional peaks appear at 1023 and 1005 cm−1 indicating the effect of SnO2 in the vanadate crystalline matrix such that there is an elongation of V=O bond. Since the crystalline matrix is affected, we can expect similar effect in the glass matrix also.
Ponnada TejeswaraRao,BalireddyVasundhara, (2015) Thermal and FT-IR Properties of Semiconducting SnO2-PbO-V2O5 Glass System. New Journal of Glass and Ceramics,05,53-58. doi: 10.4236/njgc.2015.53007