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Glass forming ability and crystallization in the PbO-Al2O3 system
Journal of Non-Crystalline Solids 44 (1981) 107-112 North-Holland Publishing Company
107
GLASS FORMING ABILITY AND CRYSTALLIZATION IN THE PbO-A1203 SYSTEM I-Iideki MORIKAWA *, Joceline JEGOUDEZ, Charles MAZIERES Laboratoire de Physicochimie Mindrale, Universitd de Paris Sud, 91405 Orsay, France and
Alex REVCOLEVSCHI Laboratoire de Chimie Appliqude, Universitd de Paris Sud, 91405 Orsay, France
Received 15 December 1979 Revised manuscript received 17 June 1980
The formation of glass by the splat-quenching of PbO-AI20 a melts was confirmed in the range 67-95 mol.% PbO. The crystallization of the glasses obtained in this way was examined by thermal analysis, dark field microscopy, X-ray diffraction and IR spectroscopy. This crystallization is generally a two-step process: orthorhombic PbO crystallizes first around 280-360°C depending on the composition, then the aluminate PbO • AI203 crystallizes around the rather constant temperature of 600°C.
1. Introduction The formation of non-crystalline solids from the melt in the PbO-A1203 system has been investigated by using the splat-quenching technique. Al203 has never been obtained as a non-crystalline solid by quenching from the melt [ 1 - 3 ] . Splatquenching of PbO [1] has led to yellow orthorhombic massicot, the high temperature form of PbO. However, it has been claimed [4] that a rapid quenching of PbO2, which is known to decompose into PbO before melting, led to a non-crystalline material. In the PbO-Al203 system, the formation of glass by conventional quenching was found for compositions around 50 mol.% PbO [5], and compositions leading to non-crystalline materials by rapid quenching were reported in the range 6 7 - 9 0 [6] and 5 0 - 9 5 mol.% PbO [7]. However, the nature of the splatquenched samples has not thoroughly been investigated.
* Present address: Research Laboratory of Engineering Materials, Tokyo Institute of Technology, 4259 Nagatsuda, Midori-ku, Yokohama 227, Japan. 0022-3093/81/0000-0000/$02.50 © North-Holland
108
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H. Morikawa et al. / Glass f o r m i n g ability
2. Experimental High purity lead oxide (Koch Light Company) and high specific surface aluminium oxide [8] were blended into starting mixtures of various compositions. After premelting using a plasma torch the mixtures were rapidly melted in a small (~20 mm a) induction heated platinum crucible which had a 0.8 mm diameter hole in the bottom. The melt was splat-quenched onto a glass plate substrate at a cooling rate of about 106°C/s [7]. Mixtures were kept molten for only several seconds. This melting duration was chosen as a result of a compromise between the need to avoid the volatilization of the component and the necessity to allow for sufficient mixing. Micro-DTA experiments were carried out in an argon atmosphere. X-ray diffractograms were obtained using a Debye-Scherrer camera. Infrared (Jr) spectra were obtained as Kbr disks.
3. Results and discussion
Splat-quenching of PbO melts yielded materials giving clear X-ray lines and an ir band (350 cm -~) of orthorhombic PbO, sometimes with very weak and broad lines of red tetragonal litharge, the low temperature form of PbO. The DTA curve of the splat-quenched sample shows a fiat exotherm around 280°C, which can be ascribed either to the crystallization of a small non-crystalline fraction of the material or to the growth of micro-crystals, or to the transformation of some orthorhombic PbO into tetragonal PbO. Neither the X-ray diagrams, nor the ir spectra permit discarding any of these hypotheses. The corresponding material is of high chemical reactivity, rapidly converts to PbaO4 in air at 400°C, and rapidly reacts at room temperature with CO2 and H20 to form lead hydrocarbonate.
.0.1"C
(A) 67'/, PbO
(B) 75*/, ~ ' ~ . . . _
L
I
' 700 C) Fig. 1. DTA thermograms of splat-quenched PbO-A120 a glasses in an argon atmosphere at a heating rate of 15°C/min. (A) 67 mol.%PbO. (B) 75 mol.% PbO. (C) 85 mol.%PbO. ~.00
300
400
5O0
600
H. Morikawa et al. / Glass forming ability
109
For compositions ranging from 67-95% PbO, the splat-quenched samples are yellow platelets. Although the violent volatilization of PbO is observed during melting, the chemical analysis of the soluble fraction gives a few per cent more PbO than predicted from the starting mixture. For instance, the starting mixture of 70% PbO gives 73.6% PbO after splat-quenching. We assume that this compositional change is caused by the presence of A12Oa which remains unreacted during melting and is not soluble in chemical analysis. We also assume that this fraction of Al203 does not react with the main glassy fraction when the sample is reheated. The DTA curves (fig. 1) for splat-quenched samples show that crystollization has a two-step
I
I
i
!
I
I
I
(B)
(c)
~ooo
L
I
8oo
l
6oo
400
~O(c.d)
Fi 8. 2. Infrared spectra o f a 67 too|.% PbO sample. (A) As-splatted. (B) After a DTA run up to 450°C. (C) After a D T A r u n up to 650°C.
110
H. Morikawa et al. / Glass forming ability
character if a small peak around 430°C for the 67% PbO sample is neglected. The orthorhombic PbO appears first between 280 and 360°C, the temperature of crystallization decreasing with increasing PbO content and PbO. A1203 crystallizes secondly at an almost constant temperature of 600°C. It should be noted the corresponding equilibrium phases would be tetragonal PbO and 2 PbO • A1203 [9]. Figure 2 shows the ir spectra of a 67% PbO sample as-splatted, after a DTA run up to 450°C and after a DTA run up to 650°C. Fig. 3 gives the corresponding spectra for an 85% PbO sample. The shallow absorption bands at approximately 800 and 600 cm -1 of the samples after crystallization of PbO (figs. 2(B) and 3(B)] seem to corrrespond to the strong ones at 800 and 630 cm -1 of the crystalline PbO • A12Oa [fig. 4(B)], suggesting the structural similarity between them. For compositions ranging from 50 to 67% PbO, the high temperature liquidus and the strong volatilization tendency of PbO made the experimental procedure I
1
I
I
1
I
I
I
l
i
l
I
CA)
(C)
11
~ooo ~o 6oo 4oo 2oo(cm~) Fig. 3. Infrared spectra of an 85 mol.%PbO sample. (A) As-splatted. (B) After a DTA run up to 400°C. (C) After a DTA run up to 650°C.
H. Morikawa et al. / Glass forming ability l
1 1000
1
I ~0
I
1
I 600
I
1
I
t /.00
111 I
I 200(cm-1)
Fig. 4. Infrared spectra of the crystalline definite compounds in the PbO-A120 3 system. (A) 2 PbO • AI~O 3. (B) PbO • A1203. (C) PbO • 6 AI203.
inappropriate. The glass formation is confirmed by DTA, however, ot-A1203 is detected by X-ray diffraction and DTA curves are not uniform among samples. This fact indicates that samples are inhomogeneous probably due to insufficient mixing of the melt. X-ray diffraction, DTA and ir spectrometry demonstrate the glass formation in the range 67-95% PbO. However, dark field microscopy showed some very minute crystalline aggregates. The glass formation appears to be easiest around 85% PbO, i.e., near the eutectic composition [10] where glasses are obtained even by the splat-quenching onto a copper plate substrate which shows poor wettability towards the melt.
112
H. Morikawa et aL / Glass forming ability
Glass formation in the PbO rich region probably results from the low temperature liquidus [10] as well as the relatively strong covalent P b - O bond. A small amount of the conditional glass former hinders PbO crystallizing out from the melt because of the directional nature of P b - O bonding. A1203 and Ga203 belong to the conditional glass formers and their 1 : 1 compound with a modifier of CaO, SrO, BaO, or PbO has a "stuffed tridymite" or related structure [11]. All these compounds can be quenched to glasses and their glass forming ability is related to the structural similarity with SiO2, which satisfies Zachariasen's criteria [ 10]. Although the detailed structure of the PbO-A1203 glasses is not known, it can be imagined that they contain locally organized clusters of definite compositions of PbO • A1203 and PbO, which precipitate as compounds upon heating. In connection with crystallization of non-crystalline materials prepared by various methods, it may be noted that dundasite [ P b 2 A 1 4 ( C O 3 ) 4 ( O H ) 8 " 3 H20] loses CO2 and H20 at around 300°C, yielding a non-crystalline material which resists crystallization of PbO • A1203 up to 640°C [12]. A sharp DTA peak indicates that crystallization is rapid once started. The formation of PbO • A1203 by reaction of PbO with alurninium hydroxide starts at about 720°C while the formation of PbO • A1203 by crystallization of PbO-A1203 glasses occurs at about 600°C. The authors thank Dr. J.P. Audi6re (Universit6 de Paris Sud) for help with the optical microscopy. H. Morikawa would like to thank Prof. S. Iwal (Tokyo Institute of Technology) and CROUS de Versailles for giving him the chance to come and join the Paris-Sud University at Orsay.
References [1] P.T. Sarjeant and R. Roy, J. A_rn.Ceram. Soc. 50 (1967) 500. [2] L.E. Topoi, D.H. Hengstenberg, M. Blander, R.A. Happe, N.L. Richardson and L.S. Nelson, J. Non-Crystalline Solids 12 (1973) 377. [3] R. Krepski, K. Swyler, H.R. Carleton and H. Herman, J. Mat. Sci. 10 (1975) 1452. [4] A. Winter, J. Am. Ceram. Soc. 40 (1957) 54. [5] A. Harari and J. Th6ry, C.R. Acad. Sci. 264 (1967) 84. [6] P.T. Sarjeant and R. Roy, Reactivity of solids, eds., J.W. Mitchell, R.C. DeVries, R.W. Roberto and P. Cannon (Wiley, New York, 1969) p. 725. [7] P. Kantor, A. Revcolevschiand R. Collongues, J. Mat. Sci. 8 (1973) 1359. [8] J. Beauf'fls,R. Setton and C. Mazi6res, J. Am. Ceram. Soc. 61 (1978) 61. [9] K. Torkar, H. Krischner and H. Moser, Ber. Dtsch. Keram. Ges. 43 (1966) 259. [ 10] H. Rawson, Inorganic glass-formingsystems (Academic, New York, 1967). [11] M.J. Buerger, Am. Miner. 39 (1954) 600. [12] C. Beaumont and C. Guillemin, Bull. Soc. Franq. Min6r. Crist. 83 (1960) 121.
107
GLASS FORMING ABILITY AND CRYSTALLIZATION IN THE PbO-A1203 SYSTEM I-Iideki MORIKAWA *, Joceline JEGOUDEZ, Charles MAZIERES Laboratoire de Physicochimie Mindrale, Universitd de Paris Sud, 91405 Orsay, France and
Alex REVCOLEVSCHI Laboratoire de Chimie Appliqude, Universitd de Paris Sud, 91405 Orsay, France
Received 15 December 1979 Revised manuscript received 17 June 1980
The formation of glass by the splat-quenching of PbO-AI20 a melts was confirmed in the range 67-95 mol.% PbO. The crystallization of the glasses obtained in this way was examined by thermal analysis, dark field microscopy, X-ray diffraction and IR spectroscopy. This crystallization is generally a two-step process: orthorhombic PbO crystallizes first around 280-360°C depending on the composition, then the aluminate PbO • AI203 crystallizes around the rather constant temperature of 600°C.
1. Introduction The formation of non-crystalline solids from the melt in the PbO-A1203 system has been investigated by using the splat-quenching technique. Al203 has never been obtained as a non-crystalline solid by quenching from the melt [ 1 - 3 ] . Splatquenching of PbO [1] has led to yellow orthorhombic massicot, the high temperature form of PbO. However, it has been claimed [4] that a rapid quenching of PbO2, which is known to decompose into PbO before melting, led to a non-crystalline material. In the PbO-Al203 system, the formation of glass by conventional quenching was found for compositions around 50 mol.% PbO [5], and compositions leading to non-crystalline materials by rapid quenching were reported in the range 6 7 - 9 0 [6] and 5 0 - 9 5 mol.% PbO [7]. However, the nature of the splatquenched samples has not thoroughly been investigated.
* Present address: Research Laboratory of Engineering Materials, Tokyo Institute of Technology, 4259 Nagatsuda, Midori-ku, Yokohama 227, Japan. 0022-3093/81/0000-0000/$02.50 © North-Holland
108
'
H. Morikawa et al. / Glass f o r m i n g ability
2. Experimental High purity lead oxide (Koch Light Company) and high specific surface aluminium oxide [8] were blended into starting mixtures of various compositions. After premelting using a plasma torch the mixtures were rapidly melted in a small (~20 mm a) induction heated platinum crucible which had a 0.8 mm diameter hole in the bottom. The melt was splat-quenched onto a glass plate substrate at a cooling rate of about 106°C/s [7]. Mixtures were kept molten for only several seconds. This melting duration was chosen as a result of a compromise between the need to avoid the volatilization of the component and the necessity to allow for sufficient mixing. Micro-DTA experiments were carried out in an argon atmosphere. X-ray diffractograms were obtained using a Debye-Scherrer camera. Infrared (Jr) spectra were obtained as Kbr disks.
3. Results and discussion
Splat-quenching of PbO melts yielded materials giving clear X-ray lines and an ir band (350 cm -~) of orthorhombic PbO, sometimes with very weak and broad lines of red tetragonal litharge, the low temperature form of PbO. The DTA curve of the splat-quenched sample shows a fiat exotherm around 280°C, which can be ascribed either to the crystallization of a small non-crystalline fraction of the material or to the growth of micro-crystals, or to the transformation of some orthorhombic PbO into tetragonal PbO. Neither the X-ray diagrams, nor the ir spectra permit discarding any of these hypotheses. The corresponding material is of high chemical reactivity, rapidly converts to PbaO4 in air at 400°C, and rapidly reacts at room temperature with CO2 and H20 to form lead hydrocarbonate.
.0.1"C
(A) 67'/, PbO
(B) 75*/, ~ ' ~ . . . _
L
I
' 700 C) Fig. 1. DTA thermograms of splat-quenched PbO-A120 a glasses in an argon atmosphere at a heating rate of 15°C/min. (A) 67 mol.%PbO. (B) 75 mol.% PbO. (C) 85 mol.%PbO. ~.00
300
400
5O0
600
H. Morikawa et al. / Glass forming ability
109
For compositions ranging from 67-95% PbO, the splat-quenched samples are yellow platelets. Although the violent volatilization of PbO is observed during melting, the chemical analysis of the soluble fraction gives a few per cent more PbO than predicted from the starting mixture. For instance, the starting mixture of 70% PbO gives 73.6% PbO after splat-quenching. We assume that this compositional change is caused by the presence of A12Oa which remains unreacted during melting and is not soluble in chemical analysis. We also assume that this fraction of Al203 does not react with the main glassy fraction when the sample is reheated. The DTA curves (fig. 1) for splat-quenched samples show that crystollization has a two-step
I
I
i
!
I
I
I
(B)
(c)
~ooo
L
I
8oo
l
6oo
400
~O(c.d)
Fi 8. 2. Infrared spectra o f a 67 too|.% PbO sample. (A) As-splatted. (B) After a DTA run up to 450°C. (C) After a D T A r u n up to 650°C.
110
H. Morikawa et al. / Glass forming ability
character if a small peak around 430°C for the 67% PbO sample is neglected. The orthorhombic PbO appears first between 280 and 360°C, the temperature of crystallization decreasing with increasing PbO content and PbO. A1203 crystallizes secondly at an almost constant temperature of 600°C. It should be noted the corresponding equilibrium phases would be tetragonal PbO and 2 PbO • A1203 [9]. Figure 2 shows the ir spectra of a 67% PbO sample as-splatted, after a DTA run up to 450°C and after a DTA run up to 650°C. Fig. 3 gives the corresponding spectra for an 85% PbO sample. The shallow absorption bands at approximately 800 and 600 cm -1 of the samples after crystallization of PbO (figs. 2(B) and 3(B)] seem to corrrespond to the strong ones at 800 and 630 cm -1 of the crystalline PbO • A12Oa [fig. 4(B)], suggesting the structural similarity between them. For compositions ranging from 50 to 67% PbO, the high temperature liquidus and the strong volatilization tendency of PbO made the experimental procedure I
1
I
I
1
I
I
I
l
i
l
I
CA)
(C)
11
~ooo ~o 6oo 4oo 2oo(cm~) Fig. 3. Infrared spectra of an 85 mol.%PbO sample. (A) As-splatted. (B) After a DTA run up to 400°C. (C) After a DTA run up to 650°C.
H. Morikawa et al. / Glass forming ability l
1 1000
1
I ~0
I
1
I 600
I
1
I
t /.00
111 I
I 200(cm-1)
Fig. 4. Infrared spectra of the crystalline definite compounds in the PbO-A120 3 system. (A) 2 PbO • AI~O 3. (B) PbO • A1203. (C) PbO • 6 AI203.
inappropriate. The glass formation is confirmed by DTA, however, ot-A1203 is detected by X-ray diffraction and DTA curves are not uniform among samples. This fact indicates that samples are inhomogeneous probably due to insufficient mixing of the melt. X-ray diffraction, DTA and ir spectrometry demonstrate the glass formation in the range 67-95% PbO. However, dark field microscopy showed some very minute crystalline aggregates. The glass formation appears to be easiest around 85% PbO, i.e., near the eutectic composition [10] where glasses are obtained even by the splat-quenching onto a copper plate substrate which shows poor wettability towards the melt.
112
H. Morikawa et aL / Glass forming ability
Glass formation in the PbO rich region probably results from the low temperature liquidus [10] as well as the relatively strong covalent P b - O bond. A small amount of the conditional glass former hinders PbO crystallizing out from the melt because of the directional nature of P b - O bonding. A1203 and Ga203 belong to the conditional glass formers and their 1 : 1 compound with a modifier of CaO, SrO, BaO, or PbO has a "stuffed tridymite" or related structure [11]. All these compounds can be quenched to glasses and their glass forming ability is related to the structural similarity with SiO2, which satisfies Zachariasen's criteria [ 10]. Although the detailed structure of the PbO-A1203 glasses is not known, it can be imagined that they contain locally organized clusters of definite compositions of PbO • A1203 and PbO, which precipitate as compounds upon heating. In connection with crystallization of non-crystalline materials prepared by various methods, it may be noted that dundasite [ P b 2 A 1 4 ( C O 3 ) 4 ( O H ) 8 " 3 H20] loses CO2 and H20 at around 300°C, yielding a non-crystalline material which resists crystallization of PbO • A1203 up to 640°C [12]. A sharp DTA peak indicates that crystallization is rapid once started. The formation of PbO • A1203 by reaction of PbO with alurninium hydroxide starts at about 720°C while the formation of PbO • A1203 by crystallization of PbO-A1203 glasses occurs at about 600°C. The authors thank Dr. J.P. Audi6re (Universit6 de Paris Sud) for help with the optical microscopy. H. Morikawa would like to thank Prof. S. Iwal (Tokyo Institute of Technology) and CROUS de Versailles for giving him the chance to come and join the Paris-Sud University at Orsay.
References [1] P.T. Sarjeant and R. Roy, J. A_rn.Ceram. Soc. 50 (1967) 500. [2] L.E. Topoi, D.H. Hengstenberg, M. Blander, R.A. Happe, N.L. Richardson and L.S. Nelson, J. Non-Crystalline Solids 12 (1973) 377. [3] R. Krepski, K. Swyler, H.R. Carleton and H. Herman, J. Mat. Sci. 10 (1975) 1452. [4] A. Winter, J. Am. Ceram. Soc. 40 (1957) 54. [5] A. Harari and J. Th6ry, C.R. Acad. Sci. 264 (1967) 84. [6] P.T. Sarjeant and R. Roy, Reactivity of solids, eds., J.W. Mitchell, R.C. DeVries, R.W. Roberto and P. Cannon (Wiley, New York, 1969) p. 725. [7] P. Kantor, A. Revcolevschiand R. Collongues, J. Mat. Sci. 8 (1973) 1359. [8] J. Beauf'fls,R. Setton and C. Mazi6res, J. Am. Ceram. Soc. 61 (1978) 61. [9] K. Torkar, H. Krischner and H. Moser, Ber. Dtsch. Keram. Ges. 43 (1966) 259. [ 10] H. Rawson, Inorganic glass-formingsystems (Academic, New York, 1967). [11] M.J. Buerger, Am. Miner. 39 (1954) 600. [12] C. Beaumont and C. Guillemin, Bull. Soc. Franq. Min6r. Crist. 83 (1960) 121.