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The hydrogarnets Ba3In2(OH)12 and Ba3Sc2(OH)12
Mat. Res. Bull. Vol. IZ, pp. 161-164, 1977. P e r g a m o n Press, Inc. Printed in the United States.
THE HYDROGARNETS
Ba31n2(OH)12
AND Ba3Sc2(0H)I 2
W. Kwestroo, H.C.A. van Gerven and H.A.M. Philips Research Laboratories Eindhoven - The Netherlands
(Received D e c e m b e r
van Hal
13, 1976; C o m m u n i c a t e d by G. H. Jonker)
ABSTRACT Two new h y d r o g a r n e t s B a 3 1 n 2 ( 0 H ) l 2 and Ba3Sc2(0H)I 2 have been prepared: a. by heating the mixed hydroxides in an autoclave at 400oc for 24 hours and b. by precipitating a mixture of soluble salts with very concentrated (12N) Na0H and refluxing the reaction product. Efforts to prepare other Ba hydrogarnets by these methods failed. X-ray data and some chemical properties of the new compounds are added.
Introduction In a paper published earlier i) we mentioned a number of compour in the system Ba0-1n20 ~. One of these compounds, Basin206 at room temperature react~ with moist air to form a ne~ cublc compound. From X-ray analysis it was found that after 21 hours considerable quantity of the compound had been formed, and afte~ 48 hours the transformation was complete. This compound proved t be the hitherto unknown hydrogarnet, Ba~In2(0H)1o. Hydrogarnets may formally be derived from normal gar~ets, A~B~(Si0~)~, by leaving out the Si ~+ ions and replacing the 02 ~ ~ons ~y~OHior Since no Ba hydrogarnets were yet known to us, we tried: a. to develop methods of preparing Baxln2(OH ) and b. to determine whether other Ba garn@ts can ~ ' m a d e by one of these methods. In this study the methods mentioned in literature for the synthesis of hydrogarnets are compared and discussed; they are evaluated for the synthesis of Ba~In2(0H)l 9. Next we investigated the existence of other Ba-h~drogarne~s, and tried to prepare these compounds by the same methods.
162
W. K W E S T R O O ,
et al
Vol.
l Z , ]:
Review of methods used for the preparation of hydrogarnets Several methods for the preparation of h y d r o ~ r n e t s have been reported in the literature. Ito and Frondel ~J prepared a lar~ number of hydrogarnets (most containing Si) by aging precipit~ obtained by adding Na0H solutions to HCI or HN0~ solutions of metal oxides. Using this method they made Ca and Sr hydrogarn~ Examples are Sr~In2(0H)lp , S r ~ S c ~ ( 0 H ) ~ e a ~~e ~ 2~~-H~~-2~~-y d r o~. ~ Schwarz 3) mentions two-meth6ds~for garnets. The first one consists in precipitating a mixture of divalent and trivalent metal-perchlorates with concentrated N~ (about 3 N) and refluxing the thus formed precipitate at 100o( for 6-12 hours. The second method consists in heating compound compositions M~ II M~III0~ with water in an autoclave at 150-200°C for ~ome ~ays.~The first method is the same in print as the preparation given by Ito and Frondel. For the second method oxidic compounds of the stoichiometric composition hav~ exist, which is indeed the case for Basin206. Another interest paper is the one published by Ivanov-E~in and co-workers *~. developed a method for the preparation of what they call alka] earth element hydroxoscandates. The composition of these hydroxoscandates, given as A3~Sc(0H) ~ , (where A = Ca, Sr or is identical with the composition of~t~e hydrogarnets. The X-~ diffraction powder diagrams mentioned in their paper, however, are quite different. Experiments Experiments
and Results
in an autoclave
First, experiments were done with the view of preparing Ba~In~ As Ba~Inp(0H)1~ is already formed in moist air from B~xlnod~, ~ the a~to~lave-~reparation method reported by Schwarz~)~seSm~d very promising. Heating Baxlno0 ~ with water in an autoclave at 200oc for 48 hours indeed ~es~l~ed in the complete formation c the cubic compound. Comparable experiments with a stoichiometr mixture of Ba(0H)~ and In(0H)~ delivered only a small amount c hydrogarnet after-90 hours. W~en the temperature is increased 400oc, a 24 hours heating gives a nearly complete formation of Baxlno(OH)Ip. When 2 N Na0H is used as reaction medium instea~ wa~er~ a c6~plete formation of B a ~ I n o ( 0 H ) ~ occurs. ~+ ~ ~ ~+ As Sc has nearly the same ionmc" radius as In , we also tr~ed~j t synthesize B a ~ S c ~ ( 0 H ) ~ . As no compound Ba~Sc~Oc is known Schwarz method, ~ e a t i ~ MxlIMglIIo~ with w~te~ ~ould not be applied, but heating Ba(0N) o ~nd S~(OH)x as a stoichiometric mixture in a ratio 3:2 with~2 N NaOH in'an autoclave at 400oc 95 hours, resulted in a compound with the garnet structure, per Ba3Sc2(OH)12~ Precipitation reactions Precipitation reactions after Schwarz 3) or Ito and Frondel 2) to disappointing results. No hydrogarnet could be detected and compounds formed could not be identified. Next we tried the me of I v a n ~ - E m i n : a saturated solution was made of Ba(OH)~ in NaOH; then a solution of scandium acetate was added. Aft$r
Vol.
12., N o . 2,
HYDROGARi~ETS
163
refluxing for some hours the precipitate was filtered and dried in a C02-free atmosphere. Surprisingly the X-ray diagram of our product showed no resemblance to the X-ray data given by Ivanov-Emin et al. Instead, some BaxSc2(OH)1~ was formed, and after refluxing the mixture for 24 ~ours we {ound nearly pure BaxSco(OH)~o hydrogarnet. Therefore we investigated whether this me~ho~ cou1~ also be applied to the synthesis of Bazln2(OH)ip. Adding a solution of InAc~ to a Ba(OH) 2 solution in~12 N. NaOMi an refluxing for about 6 hours, resulted in nearly pure B a ~ I n ~ ( O E ) ±~~ Close exam/natmon of the three precmpztatzon methods sh~ws that the only relevant difference between the experiments of IvanovEmin and of Schwarz or Ito and Frondel is that the first mentioned uses a highly concentrated Na0H reaction medium. Repeating the Schwarz precipitation reaction of In(ClOa)~ and Ba(ClOa)p with hot 12 N NaOH instead of 3 N, resulted in ~he formatio~ of pure Baxln2(OH) 2 hydrogarnet. The corresponding Sc compound could also ~e made ~y this improved precipitation reaction. •
•
•
•
•
~
Experimental procedure: 6,25 grams of BaCI 2 are dissolved in 30 ml CO o free demiwatero 1,38 grams of Sc20 x are dissolved in 30 ml 7 N HCI by slowly heating on a water~ath. In a N o atmosphere, a solution of 300 ml 12 N NaOH is prepared by dissolving NaOH in C02-free demiwater, and the mixture of the dissolved chlorides is added dropwise to this NaOH solution at 90oc whilst stirring continuously. The reaction mixture is heated for one night at 90°C to complete the reaction. The precipitate is filtered and washed with ethanol. After vacuum drying at 25°C for 20 hours, the water content of the crystalline product is 0.04 percent by weight. The yield is 6.5 grams of X-ray analytical pure garnet. According to wet-chemical'analysis the Ba content was 59.6% (theor. for Ba3Sc2(OH)12: 58.3%) and the Sc content 12.7% (theor. 12.8%). Search for other Ba hydrogarnets A second aim of this investigation was to look for other Ba hydrogarnets by the improved methods. Hydrogarnets containing trivalent ions smaller than Sc3+ or In 3~, are Ba Fe 2 (OH) L 2 and BaxGap(OH)12 , whereas, those containing rare earth zons are ex~mpIes of Ba hydrogarnets with trivalent ions larger than In3+ or Sc3+. We tried to synthesize BaxFeo(OH)Ip, BaxGap(OH)12, BaxY2(0H)12, BaxLao(OH)lo and BaxYbp(0H~Ip~by h@ating~the hyd~Sx id@s in an autodlaVe at ~00oc fo~ about 95 hours. Neither of the resulting powders contained a compound w~th hydrogarnet structu: The precipitation method (refluxing the appropriate hydroxides i: 12 N Na0H) was applied for the synthesis of BaxFe~(OH)1~ and BaxYo(OH)12. Neither of these compounds were fdun~ wit~-this me~h~d° I~ seems very likely therefore, that only two Ba-contain hydrogarnets exist: Ba31n2(OH)12 and Ba3Sc2(OH)12.
X-ray data_an d some chemical properties B_~a3S_~c2(OH)12
of Ba31n2(OH)12 a n d
The new compounds were investigated with the aid of a Philips
164
W. K W E S T R O O ,
et a l
Vol.
12., ]
X-ray diffractometer, using C o K ~ radiation ~). The data found for Ba3Sc2(0H)I 2 are : with and for
a = 14.0070 + 0.0003 Z = 8, d = ~.412 and S.G. = la3d Ba31n2(0~)l 2 : a = 14.0858 + 0.0003 Z : 8, d x = ~.019 and S.G. : la3d.
The a-values are larger than those of 2any other h y d r o g a r n e t , largest mentioned being Sr-Sc (OH)J^ ), with a = 13.53 ~. The large values for the n~w ~a h y ~ o g a r n e t s no doubt origina from the dimensions of the Ba 2+ ions. The small difference between the a-values of the In and the Sc comDound may be understood from the difference between the Sc9 + ion (0.73 ~) the somewhat larger In3+ ion (0.79 ~). Both compounds are rather stable in air. They decompose into separate hydroxides upon boiling with water. When Ba~In2(0H)l ~ heated at about 200Oc for 16 hours no decomposition ~ccurs. Some decomposition does occur at 400°C, whereas the sample heated at 800Oc clearly shows X-ray reflections of Ba51n208. This is in accordance with the results found from the experim( with the system BaO-In20 x 1). Ba~Sc2(0H)12 also showed no decomposition after heatfng for ~16 hours at 200oc. At 400°C t compound had decomposed into Ba2Sc20 ~ plus some BaC0 x. After heating at 800oc only the BaoSc205 s~ructure was found. This accordance with t ~ results ~ound from the experiments with tk system Ba0-Sc203 . References 1, W. Kwestroo, H.C.A. van Gerven and C. Langereis, Mat, Res, Bull. 12, ]57 (1977). 2. J. Ito and C. Frondel, Amer. Mineral. 52, 1105 (1967). 3. H. Schwarz, Z. Naturforsch.
B.22, 554 (1967).
4. B.N. Ivanov-Emin, L.D. Borzova, B.E. Zaitsev and R.I. Kirillova, Russ. J. Inorg. Chem. 14, 927 (1969). 5. W. Kwestroo, H.A.M. van Hal and C. Langereis, Mat. Res. Bull. 9, 1625 (1974).
Complete data have been sent to the editor of Powder Diffraction File (JCPDS).
THE HYDROGARNETS
Ba31n2(OH)12
AND Ba3Sc2(0H)I 2
W. Kwestroo, H.C.A. van Gerven and H.A.M. Philips Research Laboratories Eindhoven - The Netherlands
(Received D e c e m b e r
van Hal
13, 1976; C o m m u n i c a t e d by G. H. Jonker)
ABSTRACT Two new h y d r o g a r n e t s B a 3 1 n 2 ( 0 H ) l 2 and Ba3Sc2(0H)I 2 have been prepared: a. by heating the mixed hydroxides in an autoclave at 400oc for 24 hours and b. by precipitating a mixture of soluble salts with very concentrated (12N) Na0H and refluxing the reaction product. Efforts to prepare other Ba hydrogarnets by these methods failed. X-ray data and some chemical properties of the new compounds are added.
Introduction In a paper published earlier i) we mentioned a number of compour in the system Ba0-1n20 ~. One of these compounds, Basin206 at room temperature react~ with moist air to form a ne~ cublc compound. From X-ray analysis it was found that after 21 hours considerable quantity of the compound had been formed, and afte~ 48 hours the transformation was complete. This compound proved t be the hitherto unknown hydrogarnet, Ba~In2(0H)1o. Hydrogarnets may formally be derived from normal gar~ets, A~B~(Si0~)~, by leaving out the Si ~+ ions and replacing the 02 ~ ~ons ~y~OHior Since no Ba hydrogarnets were yet known to us, we tried: a. to develop methods of preparing Baxln2(OH ) and b. to determine whether other Ba garn@ts can ~ ' m a d e by one of these methods. In this study the methods mentioned in literature for the synthesis of hydrogarnets are compared and discussed; they are evaluated for the synthesis of Ba~In2(0H)l 9. Next we investigated the existence of other Ba-h~drogarne~s, and tried to prepare these compounds by the same methods.
162
W. K W E S T R O O ,
et al
Vol.
l Z , ]:
Review of methods used for the preparation of hydrogarnets Several methods for the preparation of h y d r o ~ r n e t s have been reported in the literature. Ito and Frondel ~J prepared a lar~ number of hydrogarnets (most containing Si) by aging precipit~ obtained by adding Na0H solutions to HCI or HN0~ solutions of metal oxides. Using this method they made Ca and Sr hydrogarn~ Examples are Sr~In2(0H)lp , S r ~ S c ~ ( 0 H ) ~ e a ~~e ~ 2~~-H~~-2~~-y d r o~. ~ Schwarz 3) mentions two-meth6ds~for garnets. The first one consists in precipitating a mixture of divalent and trivalent metal-perchlorates with concentrated N~ (about 3 N) and refluxing the thus formed precipitate at 100o( for 6-12 hours. The second method consists in heating compound compositions M~ II M~III0~ with water in an autoclave at 150-200°C for ~ome ~ays.~The first method is the same in print as the preparation given by Ito and Frondel. For the second method oxidic compounds of the stoichiometric composition hav~ exist, which is indeed the case for Basin206. Another interest paper is the one published by Ivanov-E~in and co-workers *~. developed a method for the preparation of what they call alka] earth element hydroxoscandates. The composition of these hydroxoscandates, given as A3~Sc(0H) ~ , (where A = Ca, Sr or is identical with the composition of~t~e hydrogarnets. The X-~ diffraction powder diagrams mentioned in their paper, however, are quite different. Experiments Experiments
and Results
in an autoclave
First, experiments were done with the view of preparing Ba~In~ As Ba~Inp(0H)1~ is already formed in moist air from B~xlnod~, ~ the a~to~lave-~reparation method reported by Schwarz~)~seSm~d very promising. Heating Baxlno0 ~ with water in an autoclave at 200oc for 48 hours indeed ~es~l~ed in the complete formation c the cubic compound. Comparable experiments with a stoichiometr mixture of Ba(0H)~ and In(0H)~ delivered only a small amount c hydrogarnet after-90 hours. W~en the temperature is increased 400oc, a 24 hours heating gives a nearly complete formation of Baxlno(OH)Ip. When 2 N Na0H is used as reaction medium instea~ wa~er~ a c6~plete formation of B a ~ I n o ( 0 H ) ~ occurs. ~+ ~ ~ ~+ As Sc has nearly the same ionmc" radius as In , we also tr~ed~j t synthesize B a ~ S c ~ ( 0 H ) ~ . As no compound Ba~Sc~Oc is known Schwarz method, ~ e a t i ~ MxlIMglIIo~ with w~te~ ~ould not be applied, but heating Ba(0N) o ~nd S~(OH)x as a stoichiometric mixture in a ratio 3:2 with~2 N NaOH in'an autoclave at 400oc 95 hours, resulted in a compound with the garnet structure, per Ba3Sc2(OH)12~ Precipitation reactions Precipitation reactions after Schwarz 3) or Ito and Frondel 2) to disappointing results. No hydrogarnet could be detected and compounds formed could not be identified. Next we tried the me of I v a n ~ - E m i n : a saturated solution was made of Ba(OH)~ in NaOH; then a solution of scandium acetate was added. Aft$r
Vol.
12., N o . 2,
HYDROGARi~ETS
163
refluxing for some hours the precipitate was filtered and dried in a C02-free atmosphere. Surprisingly the X-ray diagram of our product showed no resemblance to the X-ray data given by Ivanov-Emin et al. Instead, some BaxSc2(OH)1~ was formed, and after refluxing the mixture for 24 ~ours we {ound nearly pure BaxSco(OH)~o hydrogarnet. Therefore we investigated whether this me~ho~ cou1~ also be applied to the synthesis of Bazln2(OH)ip. Adding a solution of InAc~ to a Ba(OH) 2 solution in~12 N. NaOMi an refluxing for about 6 hours, resulted in nearly pure B a ~ I n ~ ( O E ) ±~~ Close exam/natmon of the three precmpztatzon methods sh~ws that the only relevant difference between the experiments of IvanovEmin and of Schwarz or Ito and Frondel is that the first mentioned uses a highly concentrated Na0H reaction medium. Repeating the Schwarz precipitation reaction of In(ClOa)~ and Ba(ClOa)p with hot 12 N NaOH instead of 3 N, resulted in ~he formatio~ of pure Baxln2(OH) 2 hydrogarnet. The corresponding Sc compound could also ~e made ~y this improved precipitation reaction. •
•
•
•
•
~
Experimental procedure: 6,25 grams of BaCI 2 are dissolved in 30 ml CO o free demiwatero 1,38 grams of Sc20 x are dissolved in 30 ml 7 N HCI by slowly heating on a water~ath. In a N o atmosphere, a solution of 300 ml 12 N NaOH is prepared by dissolving NaOH in C02-free demiwater, and the mixture of the dissolved chlorides is added dropwise to this NaOH solution at 90oc whilst stirring continuously. The reaction mixture is heated for one night at 90°C to complete the reaction. The precipitate is filtered and washed with ethanol. After vacuum drying at 25°C for 20 hours, the water content of the crystalline product is 0.04 percent by weight. The yield is 6.5 grams of X-ray analytical pure garnet. According to wet-chemical'analysis the Ba content was 59.6% (theor. for Ba3Sc2(OH)12: 58.3%) and the Sc content 12.7% (theor. 12.8%). Search for other Ba hydrogarnets A second aim of this investigation was to look for other Ba hydrogarnets by the improved methods. Hydrogarnets containing trivalent ions smaller than Sc3+ or In 3~, are Ba Fe 2 (OH) L 2 and BaxGap(OH)12 , whereas, those containing rare earth zons are ex~mpIes of Ba hydrogarnets with trivalent ions larger than In3+ or Sc3+. We tried to synthesize BaxFeo(OH)Ip, BaxGap(OH)12, BaxY2(0H)12, BaxLao(OH)lo and BaxYbp(0H~Ip~by h@ating~the hyd~Sx id@s in an autodlaVe at ~00oc fo~ about 95 hours. Neither of the resulting powders contained a compound w~th hydrogarnet structu: The precipitation method (refluxing the appropriate hydroxides i: 12 N Na0H) was applied for the synthesis of BaxFe~(OH)1~ and BaxYo(OH)12. Neither of these compounds were fdun~ wit~-this me~h~d° I~ seems very likely therefore, that only two Ba-contain hydrogarnets exist: Ba31n2(OH)12 and Ba3Sc2(OH)12.
X-ray data_an d some chemical properties B_~a3S_~c2(OH)12
of Ba31n2(OH)12 a n d
The new compounds were investigated with the aid of a Philips
164
W. K W E S T R O O ,
et a l
Vol.
12., ]
X-ray diffractometer, using C o K ~ radiation ~). The data found for Ba3Sc2(0H)I 2 are : with and for
a = 14.0070 + 0.0003 Z = 8, d = ~.412 and S.G. = la3d Ba31n2(0~)l 2 : a = 14.0858 + 0.0003 Z : 8, d x = ~.019 and S.G. : la3d.
The a-values are larger than those of 2any other h y d r o g a r n e t , largest mentioned being Sr-Sc (OH)J^ ), with a = 13.53 ~. The large values for the n~w ~a h y ~ o g a r n e t s no doubt origina from the dimensions of the Ba 2+ ions. The small difference between the a-values of the In and the Sc comDound may be understood from the difference between the Sc9 + ion (0.73 ~) the somewhat larger In3+ ion (0.79 ~). Both compounds are rather stable in air. They decompose into separate hydroxides upon boiling with water. When Ba~In2(0H)l ~ heated at about 200Oc for 16 hours no decomposition ~ccurs. Some decomposition does occur at 400°C, whereas the sample heated at 800Oc clearly shows X-ray reflections of Ba51n208. This is in accordance with the results found from the experim( with the system BaO-In20 x 1). Ba~Sc2(0H)12 also showed no decomposition after heatfng for ~16 hours at 200oc. At 400°C t compound had decomposed into Ba2Sc20 ~ plus some BaC0 x. After heating at 800oc only the BaoSc205 s~ructure was found. This accordance with t ~ results ~ound from the experiments with tk system Ba0-Sc203 . References 1, W. Kwestroo, H.C.A. van Gerven and C. Langereis, Mat, Res, Bull. 12, ]57 (1977). 2. J. Ito and C. Frondel, Amer. Mineral. 52, 1105 (1967). 3. H. Schwarz, Z. Naturforsch.
B.22, 554 (1967).
4. B.N. Ivanov-Emin, L.D. Borzova, B.E. Zaitsev and R.I. Kirillova, Russ. J. Inorg. Chem. 14, 927 (1969). 5. W. Kwestroo, H.A.M. van Hal and C. Langereis, Mat. Res. Bull. 9, 1625 (1974).
Complete data have been sent to the editor of Powder Diffraction File (JCPDS).