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16EFFECT OF COBALT DOPING ON THE OPTICAL PROPERTIES OF GLASSES IN THE ZnO-B2O3
SYSTEM
Krol I.
D. I. Mendeleev Russian University of Chemical Technology, Moscow, Russia, Senior Engineer
Sergun I.
D. I. Mendeleev Russian University of Chemical Technology, Moscow, Russia, student.
Barinova O.
D. I. Mendeleev Russian University of Chemical Technology, Moscow, Russia, PhD, Docent
Kuchuk Zh.
National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow, Russia,
PhD, Docent
ABSTRACT
Optical quality glasses in the ZnO-B2O3-CoO system with different cobalt content were obtained using the glass technology. We established the presence of absorption bands in the visible spectrum at wavelengths of 554 nm, 595 nm, and 640 nm, which indicate the presence of cobalt in the octahedral and tetrahedral states. In the infrared region a large band in the 1250-1800 nm range was found.
Keywords: Vitreous materials in the ZnO-B2O3-CoO system; absorption spectra in the visible region; infrared absorption spectra; materials for photonics.
Introduction
Glassy and glass-crystalline materials are used to create various light filters and laser materials [1-6]. They represent a promising alternative to monocrystal-line materials for solving a number of photonic problems due to a more accessible production technology [7-9]. Glasses doped with cobalt are of interest for optical instrumentation for ultraviolet light filters for various purposes [3-6]. UV filters are used in medicine, forensic medicine, geology, and radio engineering [3]. Cobalt-containing transparent materials are also used as passive Q-switches in infrared lasers due to the presence of absorption bands in the 1500 nm range [10-11].
Transparent materials doped with cobalt are characterized by the presence of a high-intensity absorption band in the visible region even at a relatively low concentration of cobalt [10-11]. A distinctive feature of cobalt-containing glassy materials is the linear form of the dependence of specific absorption on concentration. Therefore, the Bouguer-Lambert-Beer law can be applied with sufficient accuracy in a wide range of concentrations.
Low melting point of glasses in the ZnO-B2O3 system [12-15] shows that such materials are promising for industry. To date, glass formation and some chemical and physical properties of glassy materials have been studied in the ZnO-B2O3 system [14 - 16]. The boundaries of the glass formation region in the ZnO-B2O3 system were established: the lower one is 53.5 weight percent of ZnO, the higher one is 68.0 wt%. The density of glasses, depending on the ZnO/B2O3 ratio, ranges from 3.416 g/cm3 to 3.649 g/cm3 in the composition range from 55.0 up to 64.6 wt% of ZnO. Their coefficient of thermal expansion is about 48 • 10-7 deg-1. The refractive index of glass increases linearly from 1.6478 to 1.6670 with an increase in the proportion of ZnO. The chemical stability of these glasses is maximum in the range of pH = 5-7 at 80 °C, regardless of the glass composition. The destruction of the glass surface is observed in acidified or alkaline solutions. In
strongly alkaline (pH = 12) and acidic (pH = 2) solutions glass is completely destroyed. At a humidity close to 100% and a temperature of 42 - 48 °C a glass sample with the composition 69.79ZnO-30.21B2O3 wt. % lost 3M05 g / cm3 in 4 hours. The spectral characteristics (spectra in the visible and infrared regions, Raman spectra, etc.) of zinc borate glasses were studied in [1722].
The limited information about spectral characteristics and use of these materials as various optically transparent media in optoelectronics (such as light filters, Q-switches) makes it relevant to study low-melting ZnO-B2O3 and ZnO-B2O3-CoO systems.
The aim of this work is to obtain glassy materials in the ZnO-B2O3 - CoO system and study their properties.
Methodology
Transparent materials in the ZnO-B2O3-CoO system were obtained by glass technology. We considered the following compositions of the system under study: 65ZnO-35B2O3-xCoO (x = 0.00; 0.02; 0.04; 0.06; 0.08 wt.%). The ZnO, H2BO3, and CoO were previously weighed according to the composition, then thoroughly mixed and placed in corundum crucibles. Cobalt oxide was introduced over the base composition.
The 10 g batches were melted in a laboratory elec-trie furnace at 1150 °C for 2 h, then poured onto a cold metal plate, and annealed at 500 °C in an electric furnace. The glass was worked on a metal surface at a temperature of 1170 °C. To remove mechanical stress in the glass samples were annealed at a temperature of 500 °C for one hour.
The following physicochemical properties were studied. The phase composition of the obtained vitreous materials was determined by X-ray phase analysis (XPA) using an InelEquinox 2000 diffractometer, CPS 180 detector. The measurement of infrared spectra was carried out on a Bruker Tensor 27 spectrophotometer in the wavelength range of 1.25 - 2.75 ^m. The absorption spectra in the visible region were measured on a UNICO-2800 in the 200 - 1100 nm range.
Results and discussion
The obtained glass samples of the composition 65ZnO-35B2O3-xCoO, where x = 0.00; 0.02; 0.04; 0.06; 0.08 wt.% were of good quality. All samples were transparent. The obtained samples are shown in Fig. 1.
To assess the phase composition of the glasses under study, the XRD analysis of the base glass (matrix) with the composition 65ZnO-35B2O3 was carried out. The presence of halo, which is characteristic of amorphous materials, has been established.
x= 0,00 x= 0,02 x= 0,04 x= 0,06 x= 0,08
Figure 1. Appearance of vitreous materials of the composition 65ZnO-35B2O3-xCoO, where x = 0.00; 0.02; 0.04
0.06; 0.08 (wt%).
The analysis of the diffraction pattern showed the beginning of the formation of X-ray reflections of the crystallizing phase (Fig. 2). The crystallizing phases were analyzed taking into account the phase diagram of ZnO-B2O3 (Fig. 3). The base glass is in the region of the eutectic composition. This provides a low melting point of the mixture (964 ° C) and a low glass melting
140
120-
1008 80-
I—^
604020-
0
1
temperature (1150 ° C). According to the phase diagram zinc borates of two compositions can crystallize during the cooling: 5ZnO • 2B2O3 and ZnO • B2O3. The eutectic composition a-5ZnO 2B2O3 + P-ZnO • B2O3 lies on the phase diagram at 65.5 wt. % ZnO (Fig. 3) and begins to crystallize at a temperature of 961 ± 3 °C.
a-5ZnO2B2 O3
a-ZnO-B2O3 P-ZnO-B2O3
2
T
3
4
d, [A]
Figure 2. X-ray of a glassy sample of the composition 65ZnO-35B2Os
ZnO + p-5Zn0-2B203
100 B2O3
Fig. 3. Diagram of the state of the ZnO - B2O3 system [12].
<
1,0 0,8
0,6 0,4 0,2
0,0
/ N / S
/ / / /
----0,08
-------0,06
\ --------0,04
•s\ .......0,02
\ \ -0,00
\ \ \ N s N
' • • .';N ----__ :
400 450 500
550 600 650 l, nm
700 750 800
Figure 4. Absorption spectra in the 350 - 750 nm range of glassy materials with the composition 65ZnO -35B2O3 at a concentration of CoO: 0.00; 0.02; 0.04; 0.06; 0.08 wt.%.
An analysis of the crystal structures of zinc borates 5ZnO • 2B2O3 and ZnO • B2O3 showed that the zinc ion in the structure has a coordination number of 4 and forms tetrahedral groups [ZnO4]. Doping of the glass matrix increases the probability of the formation of tetracoordinated cobalt and leads to the appearance of an absorption band in the near-IR region (1.3 ^m - 1.7
^m). As a rule, in borate glasses cobalt atoms occupy tetrahedral and octahedral positions.
The introduction of cobalt leads to a blue staining of the glass of varying intensity depending on its content (Fig. 1). The absorption spectra in the visible range of 200 - 1100 nm of glassy materials of eutectic composition 65ZnO-35B2O3 with a CoO content of 0.00;
0.02; 0.04; 0.06; 0.08 wt.% are shown in Fig. 4. It was found that the cobalt ion doping results in a broad absorption band in the 425 - 700 nm range.
The linear dependence of the optical absorption coefficient of a glassy material on the concentration of CoO (Fig. 4) makes it possible to calculate the optical properties of these materials according to the Bouguer-Lambert-Beer law.
A wide absorption band of eutectic glass of the composition 65ZnO-35B2O3 with a CoO content of 0.00; 0.02; 0.04; 0.06; 0.08 wt.% consists of 3 bands with maxima at 528 nm, 582 nm and 632 nm. They can be assigned to the 4A2 (F) ^ 2A1 (G), 4A2 (F) ^ % (P), and 4A2 (F) ^ 2E (2G) transitions.
To study the coordination state of cobalt ions, the optical spectrum was analyzed by decomposition into Gaussians. The Fig. 5 shows the decomposition into Gaussians for the glass with the composition 65ZnO-35B2O3 with a CoO content of 0.06 wt.%. According to the literature [17, 19], the absorption bands in the 508.9 - 519.0 nm and 616.5 - 636.5 nm regions are due to electronic transitions 4A2 (F) ^ 2A: (G) and 4A2 (F) ^ 2E (2G) of octahedrally coordinated Co2+ ions. The absorption band in the 568.9 - 580.8 nm region caused by the electronic transition 4A2 (F) ^ 4T (P) of tetrahe-drally coordinated Co2+ ions.
■ 65ZnO-35B2 O3-0,06co0
<
1,01
0,8
0,6
0,4
0,2
0,0
4A(F)-
- 4A2(F)-4A2(F)-
2
A1(G) ^(P) >2E(2G)
400 450 500 550 600 650 700 750 800
l, nm
Figure 5. Decomposition of the absorption band into Gaussians of glass with the composition 65ZnO - 35B2O3
at a concentration of CoO: 0.06 wt.%.
Table 1.
Characteristics of absorption bands in the visible spectrum of eutectic glass of composition 65ZnO-35B2O3 with
a CoO content of 0.06 wt.%.
Area (integrated) FWHM, nm Maximum height Center, nm Relative value of the area, %
4A2(F)^2A:(G) 47,220 113,640 0,390 528,216 50,690
4A2(F)^4T:(P) 9,916 46,759 0,199 582,489 10,645
4A2(F)^2E(2G) 36,017 87,596 0,386 632,766 38,665
Area (integrated) - peak area, FWHM - half-height width, Center - maximum position.
1,0-1
0,90,80,70,6-
CO
< 0,5-1
0,40,30,2-
1500
-------0,08
------0,06
-----0,04
---0,02
-0,00
'.'il
' ■' 'l /!ii
/ -■""•s
" /
• ' I
/ '//
" /'I
/ " /
/
/
> /
2000
2500
3000
l, nm
3500
Figuire 6. Absorption spectra in the 1250 - 2750 nm (1.25 - 2.75 microns) infrared region of glassy materials of composition 62.5ZnO-37.5B2O3 at a concentration of CoO: 0.00; 0.02; 0.04; 0.06; 0.08 wt.%. All spectra are
shown shifted along the Y-axis.
Decomposition into Gaussians of the optical absorption spectrum of the glass under study with a cobalt content of 0.06 wt.% showed that the most intense is the band with a maximum at a wavelength of 528.2 nm, and the least at a wavelength of 582.5 nm.
In the study of the absorption spectrum in the infrared region of glassy materials of the composition 65ZnO-35B2Os with a CoO content of 0.00; 0.02; 0.04; 0.06; 0.08 wt.% (Fig. 6), the beginning of a broad absorption band formation in the near-IR region in the ~ 1500-1700 nm range was established. Fig. 6 shows a comparison of the spectra of glassy materials with the composition 62.5ZnO-37.5B2O3 with the concentration of CoO: 0.00; 0.02; 0.04; 0.06; 0.08 wt.% (for clarity, the spectra are shifted along the Y axis). The appearance of an absorption band in this region indicates an insignificant crystallization in the glass. With increasing Co2+ concentration, the fraction of cobalt in the tetracoordinated state in the crystalline phase increases.
The presence of a wide absorption band in the IR region in the 1250 - 1800 nm range caused by the 4A2 ^ 4T (4F) electronic transition shows that the obtained materials are promising as a Q-switch for IR lasers. Glass-ceramics based on obtained glasses will demonstrate increase in the absorption in the near-IR region due to an increase in the concentration of cobalt in the tetracoordinated state.
Conclusions
In the ZnO-B2O3-CoO system the possibility of obtaining glassy materials in corundum crucibles at a temperature of 1150 C and a working temperature of 1170 C has been investigated.
The intense absorption bands in the visible region at 554 nm, 595 nm, 640 nm correspond to the transitions 4A2 (F) ^ 2A1 (G), 4A2 (F) ^ 4T1 (P), and 4A2 (F) ^ 2E (2G). These spectral properties make obtained materials useful as a light filter for Wood's lamp. It is shown that in glassy materials of the composition 65ZnO - 35B2O3 - xCoO, where x = 0.00; 0.02; 0.04; 0.06; 0.08; wt.% Co2+ ion has tetrahedral and octahedral coordination.
For glassy materials with the composition 65ZnO-35B2O3-XC0O the broad absorption band in the infrared region (1250-1800 nm) was found. It indicates that they are potentially promising as materials for passive Q-switches.
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ВЛИЯНИЕ РАЗМЕРА ЧАСТИЦ НАПОЛНИТЕЛЯ НА ПРОЧНОСТНЫЕ СВОЙСТВА ПОЛИПРОПИЛЕНОВЫХ КОМПОЗИЦИЙ
Ищенко Н.Я.
кандидат химических наук, заведующая лабораторией
физико-химического анализа, Институт Полимерных Материалов НАН Азербайджана
Шахназарли Р.З.
кандидат химических наук, ведущий научный сотрудник лаборатории функциональных «смарт» полимеров, Институт Полимерных Материалов НАН Азербайджана,
Алиева А.М.
кандидат химических наук, научный сотрудник лаборатории светочувствительных и оптически прозрачных полимерных материалов, Институт Полимерных Материалов НАН Азербайджана
Фаттаева Д. И.
техник лаборатории функциональных «смарт» полимеров, Институт Полимерных Материалов НАН Азербайджана
Гулиев А.М.
член-корреспондент НАН Азербайджана, профессор, руководитель лаборатории функциональных «смарт» полимеров, Институт Полимерных Материалов НАН Азербайджана
