Infrared Adsorption and Dielectric Properties of Glassy Powder Of PbO-SiO2 Binary System

Infrared Absorption and Dielectric Properties of Glassy Powder of PbO-Si02 Binary System

Hisawo HAGIWARA， Ryozo OYAMADA， Toshio KUROSAWA and Tetsuo Y AGIHASHI

National Research Institute For Metals 3-12 2..(ごhomeNakamegurb Meguro-Ku， Tokyo， Japan

Received Aug. 18， 1969

The glassy state of the PbO・Si02binary system was studied by measuring the infrared absorption spec紅um，the dielectric constant and the dielec位icloss of the glassy powdel'of this system.

The infrared absorption maximum shifted from 9.1μto about 1l.2μin the wave length with the change of the composition of the system. The curve of the infrared absorption maximum VS.the composition showed a steep slope as increasing the content of PbO from 30 to 90 mol.% PbO， except three characteristic plateaus at about 50， 65 and 73 mol.% PbO. The s耐lilarpatterns were also found in the curves of the dielec位icconstant and the dielecむicloss VS.the composition. Itis proposed therefore， from above results， that a three dimensional network framed by SiOt ions may be gradually r削 uredby 02-ions of added PbO and then a new network framed by P

b

O

!

"

"

ions may begin to take tums atぬout65 mol.% PbO.

1

.

Introduction Since slags have been considered to be the interesting materials in the process metal1urgy， there are a number of reports on physical properties of slags in the liquid state， such as density， viscosi ty， surface tension and electrical conductivity. In recent years

，

some attemps have been made to expain the structure of silicate and borate systems by means of X-ray diffraction1)， 2)， electron diffraction3)， infrared spectrum叫， 5) and nuclear magnetic resonance6) methods. explain the structure of slags may be found through studying that of the materials in the glassy sta te. Owing to studying the liquid state of slags

，

rapidly cooled slags in the glassy state were sometimes used as samples because of ex -perimental difficulties. The glassy state has been considered as an intermediate state between those solid and liquid. Therefore， a clue to

The PbO・Si02system treated in the present research has some characters at the fol1owing points of view:1)the system gives a simplified example of slags， 2)the system has compara-tively low melting temperature， 3) a melt in the system becomes the crystal1ine state by the slowly cooling process， whereas 4) the same melt becomes the glassy state by the rapidly quench -mg process. The data of the dielectric constants

，

the dielectric losses and the infrared absorption spectra of the glassy samples of the PbO・Si02 system were presented here and the structure of the glassy state was discussed on the basis of the simple ions such as SiO:-，Pb2+ and 02

-J. Electrochem. Soc.Japan ご二1.75mm ー し F ー ) γ om

-: ・

1 i n リ p b A: Electrode made of Copper B:Quartz tube (hatched part) Cell for dielec仕icmeasurement

Then each sample weighed in that mass was packed into the cell， and E' and ε" were measured. In this case， it has been assumed that volume change concerning with the glassy state did not occur at every composition. 11ρ 10.0 9.0 2.1 Preparation of Glassy Powder Chemical grade lead oxide σbO) and high purity quartz powder (Si02) were used. The composition range of30~90 mol.% PbO studied in this experiment was divided every 2 mol.%. The weighed amounts of PbO and Si02 were

mixed in an agate mortar， and the mixture was melted in a platinum crucible at about 2000C over the melting point of each composition. The melt was held at that temperature for 3 hours and was stirred intermittently to obtain a homo-geneous melt. Then it was quenched by pouring and cooling in distilled water at room tem -perature. After drying at about 1000C in vacuum， the obtained glassy material was ground into powder under 250 mesh， and the glassy powder made by above procedure was stored in a vacuum desiccator， and used as the sample.

It was confirmed thata11 samples of various compositions were amorphous powder by the aid of the X-ray diffraction method. Each mole percentage was determined by the quantitative analysis of Pb (Chelate-titration). In order to examine effects of keeping time of above meltingstateon the physical properties， melts held for 5， 10 and 30 hoursa1so were prepared. However， the keeping time dependence was little.

2

.

Experimental 194 Fig.l 100 20 n u n -G O Q U ? と c E て C -∞ 4O 2.2 Apparatus The infraredabsorptionspectra of the glassy samples were observed with a DS・401G model diffraction grating infrared spectro・photometer

(Nippon BunkδKogyo Co.). The samples used for the infrared absorption measurement were prepared by pressing the mixture of the glassy samples (about 5 mg) and chemical grade KBr powder (700 mg) in vacuum. The dielectric constants E' and the dielectric losses E" of the glassy samples were measured by a type TR・10dielectric loss measuring set (Ando DenkiCo

ふ

Thecell (320 m m in diameter， 1口..7 m m in thickness) used for the measurement waおs illustrated in Fi惚g.1. lnfrared absorption curves. Numerical valuesinthe fi伊reshow mole % of PbO 9.0 10.0 11.0 ¥1'.、(>h'ngthl/l!

。

Fig.2 In order to take theconstantvolume， limited by the cell， of the glassy samples， each mass of them was calculated from the cell volume and the arithmetic average density of each composition.

3. Results The observed infrared absorption curves to each composition are shown inFig.2. One of modes of the Si044・ionis known as the triply degenerate stretching vibration， 内 mode8)， which was observed in this experiment.V3 mode is characterized by a largeabsorption in the infrared associated with the antisymmetry motionof the Si044-ion. In order to show the change ofV3 mode with each composition， the curve of the absorption maximum to the mole concentration of PbO isshown togetherwith the phaseequilibrium diagram7) forthePbO・Si02 system in Fig. 3. As shown in this figure， it is obvious that V3 mode is apparantly responsible to variationof thecompositionof thesystem. Namely， the observed absorption maximum shifts from9.1μ(pure silica) to about 11.2μ(90 mol.% PbO).Thisfeatureis in good agreement with the resuJtsof Suginohara and Yanagase4). The degree oftheshiftof the absorption maximum increases gradually with increasing the content of PbO up to 30 mol.% PbO and then increases rapidly with increasingthecontent up to50 mol.%. As thecontent of PbO is more and I-l <;RO コ ・4 ' "L <!I

E

7001 。 IPbO ... ト I~4PbO 'SiO

，

Qlla.rtz 11.0 p a n u n u . n u -a -a ( 孔 ) 占 “ 国 戸 ﹄ ω -_mw h_M， Y J P

~

¥

9.5 9.0 100 80 60 40 .20 0 PbO(mole %) Fig. 3 Phasediagram(afterGel1er) andplots of infraredabsorptionmax加umvs. mole% ofPbO more increased， thecurve of theabsorption maximum showsa steep slope except three characteristic plateaus at about 50， 65 and 73 mol.% PbO respectively. The compositioncon -taining 50 or about 65 mol.% PbO corresppnds tothe phase of PbO・Si02 or 2PbO・Si02 respectively. When thecontentof PbO is more than 90 mol.% PbO， the absorption becomes rapidly small. On the other hand， the dielectric constants e'andthe dielectric losses ε" of the glassy samples， pure silica powder and pureleadoxiae powder were measured with several frequencies: 30， 100， 300， 103_， 3XI03_{， 10}4 _and3XI04 _Hz. However， absolute values of e' and e" may not be significant， since they were those of powdered samples. Then， to obtain some informations of the giassy state， the ratio e'/e'o and e"/e"o are taken and shown tothe mole concentrationof PbO inFigs. 4， 5 respectively， wheree'0 is the dielectric constan t ofpure Si02 and e"0 isthe dielectric loss ofthat.Althoughthedielectric constant of pure PbO has been given as25.9at2 MHz and one ofcrystallinesilicaas 4.51 and 4.6/1， they were obtained as6.0 and 3.0 re -spectively in this measurement. That ofsilica 1.9 1.7 ご1.5 刷 、 ¥ w !.3 1.1 、<、 。 込

o

40 80 80 1005iO， 100 70 50 30 0 PbO mole % o : 30Hz血 3へ10ιHz Fig.4 Curves ofぜた'0vs. the composition of the system

J. Electrochem. Soc. Japan terms of the acid-base equilibrium:

I

_ _

! 司

l

(-Si-0 -Si-)+ 02-

=

2(ーSi-σ)

I

I

I

196 and concluded that the size of the macro -molecules was determined by the nature of the cation. Sridhar and Jeffes14) reported that the activities of PbO in the PbO-Si02 melts re・ presented the positive deviation from that cal -culated from the Temkin model1 5)， and pre -dicted that the positive deviation was probably due to the polymerization of SiO:-ions by the reaction of the type

w

o

5.0 C 2 山 則 ¥ E W Especially， on the PbO・Si02melts， it was studied by Kameda et al. that the temperature coefficient of surface tension 16) of the liquid lead silicate， da/dT， showed the negative devia -tion in the composition range of more than about 40 mol.% Si02 and that the viscosity17) of the system increased exponentially with de -creasing the content of Si02 below 40 mol.%. The features were explained by the increment of the number of planar ring ions such as (Sh 09)6

二

(Si4012)S-， (Si601S)6-， etc. Masson18) des -cribed that the most abundant s加glespecies of basing on the ionic equilibrium discrete silicate ion， on molar basis， is SiO:-， followed in turn by Si2 O~-， Si3

o

i

o

， .. Above reports suggest that there are large ions in the liquid lead silicate， though the ion types proposed in the reports are different one another. However， the presen t au thors will discuss the present results on the basis of more simple ions (SiO:-， Pb2+ and 0

勺

andof the simple rules of Zachariasen 19) desc巾ing1)an oxygen atom is linked to not more than two atoms M; 2) the number of oxygen atoms surrounding atoms M must be small; 3) the oxygen polyhedra share corners with each other， not edges or faces， 4) at l飽stthree corners in each oxygen polyhedron must be shared. Through the measured composition range (90~ 20 mol.% PbO)， /)3 mode of the SiO:-ion was apparently changed as increasing the content of PbO. Itmay be considered that the change is due to the change of the interaction which took place by the deviation of the relative configu -2S

i

O

:

--

.

:

Sh O~-

+

02-. ，0 Curves of(/'/e"ovs. the composition of白esystem IO'Hz 80 110Hz，ム I .Q 100 Fig.5

。

agrees in the order of magnitude of the given values， whereas that of PbO is very different to the given value. The discrepancy between these two values of PbO are considered to be due to the difference of these two samples. Every obtained curve of e'/e'oand eぜ"づ

i

作e" show similar pat悦te釘rnstωo the cωurve of the infrared absorption maximum， that is， three characteristic plateaus at near 65 and 73 mol.% PbO.

‘

As foregoing， the system becomes the glassy state when it was rapidly quenched from its liquid state. Glassy materials， in general， are described as suppercooled liquid or as solid， and their structure is considered to be a combination of order and disorder， the order occurring in small structural elements by which a three dimensional random networkisconstructed.

τ

'herefore， the relaxation. time of a non -equilibrium state is so long that the glassy materials have charactet:istic properties. Now， the theory of silicate glasses based 0，11 an equilibrium distribution of silicate ions was formulated by Huggins 10)，11). Flood and co・ workers 12)，13) discussed the silicate systems in

4

.

Discussion

ration of Si， 0 and Pb atoms. From thefact that

the absorption maximum shifts toward longer

one than9.1μ， itispredicted that the inter

-actionbetween Si and 0 atoms were disturbed by added PbO.

First， inthe regionofslow variation ofthe

absorption maximum (0-30 mol.% PbO)

，

it seems that Si-O-Si bonds of thethree dimen -sional random network framed by Si044-ionsare releasedby 02-of added PbO asaccording to the rulesof1)and 3)， st出 theSi044・tetrahedral

structure remains. Hence， this situation makes us

supposethe interactionbetween a Pb2+ ion and

two Si044-ions frarning the Si044-network* as

shown in Fig. 6 (a). The compositionof 50 mol.

。

~-

'

0ß

@①-@

-

ら

@

(a) Range01 0 -50 mole% PbO content (b) Range0150-67mole% PbOcontent Fig.6 Some simple model of the system % PbO， at which the curve of the absorption maximum (Fig.3)shows a plateau， corresponds to thecompound PbO・Si02inthephase diagrarn and seems to be a stable structure. Now， the magnitudeof the interaction(1) between a cationand an anion can be estimated as1 = 2Z/a2 _{，.where Z istheionicvalencyof the} cationand a is a separation ofthe cationand the anion. Taking the values ofOgj.o， apb.O and Z

as 1.62 A20)， 2.19 A21)，**，4 (Si-valency) and 2

(pb-valency) respectively， Isi-o and Ipb・o are obtained as 3.05 and 0.83respectively.The former is longerabout 3.7 times than the latter， so that itmay be considered thattheSi0 44-tetrahedralstructureis never broken away， even though it undergoes more orless changes at 50 mol.% PbO. However， the Si044二networkseems to be cut offby 02・ionsof added PbO at the

considerablenumber ofSi・0・Sibonds. Consider

-ing the degree of the ionic dissociation， about 50

%

，

evaluated from theelectro-negativity2 2)

，

a half ofthe contentof PbO， i.e.， one fourthmole fraction of the content of PbO seems to be ionized into Pb2+ and 02-ions atthiscomposi

-tion. Therefore， atleast one offourcornersof a Si044. ion which isa member of frarningthe

Si04 4--network， may be cut off by above ionized

02-ion， and then one cornerfreed by cutting off may be associated with non-ionized PbO (covalent bond)， and the othercornerattracts a Pb2+ ion.百ussituation， forexample， isillustrat -ed in Fig.6 (b). On the other hand，ε'/e'0 hardly varies to every frequencyat50 mol.% PbO and issmaller than one of pure Si02・Ingeneral， ionic materials show a small dielectricconstant.Hence the whole system is likely to be the state of the ionic bond and so the ionic bond between Si044-and

Pb2+ ions is considered to be preferable to the covalentone in this composition. e

づ

ε九 also shows the similar featureasabove， narnely the portion of the energy loss (L) of an appIied electric field at thiscompositionis the smaIlest of aIl others. Here the portion is represented as L

= e" E20ω/8π23)， Eo is the appIied electric field and ωis the angularfrequency.The energy loss of the applied field occurs as results of the migration of ionic speciesand of the rotation of dipoles， if they exist. From the[;仏acはtt出ha幻tεイ"/作εH has a srn凶叫a必11valueat50 mol.

%

PbO， freely movable species areconsideredto be Iittle 4- ，_. * The representation“Si04-network"shows the three dimensional random network framed by SiOrions 叫 APbatom wl)ichisa component ofleadoxidehas threecoordinationsforoxygenatomsandthe separations betweenPband 0 are2.21， 2.18 and 2.18λr田pectively.Thepresentauthors assumed that themeanvalue of them， 2.19λwas adapted becauseoftheglassy state.

198 present. The steep slope of the curve of the absorp -tionmaxirnum in the range from 30 to 50 mol.% PbO is considered to irnplies that the disturbance of the stretching vibration of the Si044-ion is beingenhanced by theassociation with covalent bond PbO and by the interaction with a Pb2+ ion. As increasing moreoverthecontent of PbO，

Si-O-Si bonds of the Si044--network are more

cut offand theSi044-tetrahedralstructure are

gradually distorted by the interactionwithPb2 +

ionsand by the association with covalent bond PbO.

In the range from 50 to 65 mol.% PbO

，

increaseof E'jE'0 and E"/E九 isseemed to e土plai負 by gradual rising of the polarizationeffectof PbO. If above evaluated. value 50% isused， one third mole fractionis ionized and so Si-O-Si bonds of the Si044--network is opened by 02

-ionsof added PbO at least one or two cornersof a Si044- ionframing the Si044--network. At this stage， the Si044--networkgoesto pieces， as therule 4) can not be satisfied.On contrary， itis presumed that grouping of covalent bond PbO beginsto forming a new three dimensional (Q)

ナ円必ート明言ー②

P

b

ぴ

0 0 0

十

.1.- -Fig.7 a: Proposed Pb046-ion model b: Structur巴oftetragonalPbO crystaJ (after Furukawa) J. Electrochem. Soc. Japan network. Thisnetwork is likely to be constructed by chains of Pb04 6-ions. The proposed Pb04 6-ion model isanalogous to the Pb04 pyramid one by

Furukawa2)， as shown in Fig. 7. From above

consideration， the composition of about 65 mol. % PbO is likely to be a forminglimitofthe Si044-network. The special concentration of about 40 mol.% Si02 reportedby Hino1 6) is near thecomposition of about 65 mol.% PbO， therefore it might be explained by above const -ructive change. As increasing the content of PbO from 65 mol.，%it should seem， at a point of statistical view， that such constitution of theg1assy state is enchanced. At 73 mo1.% PbO， the curves of E'jε'o ，ε"/ε九 and theinfraredabsorption maximum become again smooth. In this com-position， thenetworkism幻凶y formed by covalent bond PbO and theSi044-tetrahedral structure would beginto be broken away.

Furukawa suggested that the composition of PbO/Si02

=

2.64/1 (73mol.% PbO) was “a

glassforming lirnit"2). This suggestion issup -ported by the present experimental results.

Since pure PbO has essentially the high dielectric constant asforegoing， this considera -tion seems to be reasonable， provided groups of covalent bond PbO form a new network and appear theirlargepolarization. According tothe theory of Frank24)， total polarization ofPbO consists of theelectronicpolarization (0.652) and theatomic one (0.241)25).The effect of the

former is larger of the two. Therefore， the dielectric constants of theglassy samples become large valuesintherangeof the high content of PbO， becausethe more Pb046-ionsare formed

the more theeffectof the electronicpolarization ise凶lanced.

s

.

Conclusion Some explanationsof theglassy structure of the PbO-Si02 systemwere attempted by using the resultsofthedielectric constant， thedielect -ric lossand the infraredabsorptionma氾mum independcntly of the model of “thepolymeriza -tion ofSi044-ions

ぺ

onthe basis of thesimple ionssuch asSi044-， Pb2+ and 02-， and are

summerized as follows:

1) The glassy samples of the composition at near 50 mol.% PbO have the approx位lately

stable structure and correspond to the phase PbO・Si02in the phase equilibrium diagram. The

Si044--network is released at least a quarter corner of a Si044- ion framing the

Si044--network by 02-of added PbO， and V3 mode of

the Si044-ion is disturbed by the association with cova1ent bond PbO and by the interaction with a Pb2+ ion.

2) At the composition of about 65 mol.% PbO，

the Si044--network is ruptured and the Si044-tetrahedra1structure isa1so distorted. This com-position seems to be a 1加itof forming the glassy state which was made from the Si04 4--network. 3) In the range of the composition from 65 to 73 mol.% PbO， a new network framed by Pb046- pyramids seems to become pre -dominantly. So that， both the dielectric constant and the dielectric loss show large va1ues by the effect of the polarization of PbO， especia1ly by the electronic one. 4) This experimental results lend support to "a glass forming limit " at 73 mol.% PbO proposed by Furukawa. However， this limit is affected by a condition of quenching rate of the melts of the system. Reference:・ 1) G. J. Bair

，

J.Am. Cerarn.Soc. 19

，

339 (1936). 2) K. Furukawa， yδ，'yuen3， 587 (1960)， SCI Rep. RITUA 12 (No. 2)， (1960). 3) G. O. Bagdykiyants， A. G. Alekseev， Structure of Glass， Proc. AI1-Union Conf.Glassy state， 3rd Leningrad(1959). 4) Y. Suginoh紅a，T. Yanagase，4出YδgyoKiso-TOron Koen Yoshi-Syu p. 87， (1960). 5) W. Pepperhoff， Z. Elektrochem. 58 (No.7)， 521 (1954).

6) M. Leventhal， P. J. Bray， Phys. Chem. Glass. 6

(No.4)， (1965). 7) R. F. Gel1er， E. N. Bunting，よResearchN. B. St. 13，237(1934) 8) K. Nakamoto，“Infraredspec位aof Inorganic and Coordination Compound " p. 107(1963)， Wiely， New York. 9) Kagaku-Binran， p. 1004 (1966)， Maruzen， Japan. 10) M. L.Huggins，よ Opt.Soc. Am. 30 (No. 9)，420 (1940). 11) M.L.Huggins，よAm.Cerarn.Soc. 26 (No. 12)，393 (1943).

12) H. Flood， T. F凸rland，Acta Chem. Scand， 1 592

(1947).

13) H. Flood， T. Forland， B. Reald， ibid. (No. 9)， 790 (1947).

14) R. Sridhar， J. H. E. Jeffes， Inst. Min. Metal.C45，

Mar.， (1967).

15) M. Temkin

，

Acta Phys. Chim. URSS 20

，

411

(1945).

16) M. Hino， T. Ejima， M. Kameda， Nippon Kinzoku Gaku-KaιShi， 31 (No.2)， 113(1967). 17) T. Ejima， M. Kameda， ibid. 31 (No. 2)，120(1967). 18) C. R. Masson，よAm.Cerarn.Soc. 51 (No.3)， 134 (1968). 19) W. H. Zachariasen，よ Am.Chem. Soc. 54 3841 (1932). 20) R. Kiriyama，“Kozo Muki-Kagaku" P. 273 Kyoritsu Shuppan， Japan， 1. 21) R. Kiriyama， ibid.1， p. 129. 22)L.Pauling:“Nature of the chemical bond" Cornell University PressIthaca 2nd ed. (1945). 23) H. Frohlich，“Theory of Dielectrics" p.14 Oxford. 24) F. C. Frank， Trans. Faraday Soc. 33‘513 (1937). 25)L.J. Berberich， M. E. sell， J.Appl. Phyι11，168] (1940).