Synthesis of Barium Titanyl Oxalate by Homogeneous Precipitation from Dimethyl Oxalate Solution

702 Bull. Korean Chem. Soc. 1998, Vol. 19, No. 6 . Notes and the Y—Cu separation is about 6.3 A. There are no hy- A.; Huffman, J. C.; Streib, W. E.; Caulton, K. G. J. drgen bonds between neighboring ribbons. Addition of Cu Chem. Soc., Chem. Commun 1990, 1990. (acac)? to the benzene solution of Y(hfa)3(H2O)2 yields the 1 4. Bidell, W.; Bosch, H. W.; Veghini, D.; Hund, H.-U.; :1 adduct of [Y(hfa)3(H2O)2] [Cu(acac)2] connected through Doring, J.; Berke, H. Helvetica Chim. Acta 1993, 76, intermolec미 ar hydrogen bondings. This adduct dissociates 596. to the each component by adding polar solvents. The cry 5・ Abbreviations used in this paper include: Hhfa, hex stal structure 아 lows that [Y(hfa)3(H2O)2][Cu(acac)2] molec afluoroacetylacetone; hfa, anion of Hhfa; Hacac, acetyl ules have one-dimensional networks by intermolecular hy acetone or 2,4-pentanedione; acac, anion of Hacac. drogen bondings. Further studies on the control of 1:2 or 1: 6. North, A. C. T.; Phillips, D. C.; Mathews, F. S. Acta 3 ratio of Cu to Y metal complex through intermolecular in Crystallogr., Sect A: Cryst. Phys., Diffr., Theor. Gen. teractions are in progress in our laboratory. Crystallogr. 1968, 24, 351. Acknowledgment. Financial support of Korea Min 7 (a) Sheldrick, G. M. in SHELXS-86, A Program for Struc istry of Education (1997-1998) is gratefully acknowledged. ture Determination, University of Gottingen, Germany, 1986. (b) Sheldrick, G. M. in SHELXL-93, A Program References for Structure Refinement, University of Gottingen, Ger many, 1993. L Rao, C. N. R.; Raveau, B. Acc. Chem. Res. 1989, 22, 6. 8. (a) Kang, S.-J.; Jung, Y. S.; Sohn, Y. S. Bull. Korean 2. Cowley, A. H.; Jones, R. A. Angew. Chem., Int. Ed. Chem. Soc. 1997, 18, 266. (b) Jung, Y. S.; Lee, J. H.; Engl. 1989, 28, 1208. Sohn, Y. S.; Kang, S.-J. Bull. Korean Chem. Soc. 1998, 3. (a) Wang, S.; Smith, K. D. L.; Pang, Z.; Wagner, M. J. J. 19, 15. Chem. Soc., Chem. Commun 1992, 1595. (b) Wang, S.; 9. Pinkas, J.; Huffman, J.; Bollinger, J. C.; Streib, W. E.; Pang, Z.; Smith, K. D. L.; Wagner, M. J. J. Chem. Soc., Baxter, D. V.; Chi아 !이 m, M. H.; Caulton, K. G. Inorg. Dalton Trans, 1994, 955. (c) Bidell, W.; Shklover, V.; Chem. 1997, 36, 2930. Berke, H. Inorg. Chem. 1992, 31, 5561. (d) Vaartsra, B. Synthesis of Barium Titanyl Oxalate by Homogeneous Precipitation from Dimethyl Oxalate Solution Myounghee Lim, Wooyoung Huh, and Chui Lee* Research Institute for Natural Sciences and Department of Chemistry, Hanyang University, Seoul 133-791, Korea Received February 14, 1998 Barium titanate (BT) is considered an attractive material In this case, however, the morphology of BTO was found as its ceramics are widely used in electronic components to be multisized instead of being monosized. The final bar- such as multilayer capacitors and nonlinear resistors.1,2 In ium titanate (BT) powders were about 3 |im in diameter order to produce high-quality ceramics, the starting powders and consisted of different phases.6 require to have a uniform particle size and 아 iape『 Similarly, In the present study, dimethyl oxalate (DMO) and chloride the powder of barium titanyl oxalate (BTO), known as the ions were 아 losen as an oxalate anion source and as sup precursor of BT, need to have a unifonn particle size and porting anions respectively. The primary purpose of present shape. In order to obtain BTO powder with such a high study is to investigate systematically the influence of experi- quality, a homogeneous precipitation method has been mental variables such as DMO concentrations, chloride con adopted. centrations, temperatures, aging times and etc. on the pro A common way of homogeneous precipitation methods perties and morphology of the BTO particles produced. are the controlled release of precipitants by another chem ical source in the solution. Diethyl oxalate (DEO), which Experimental can slowly decompose to yield oxalate ions, had been used as the precipitant source by present authors45 and was A stock solution of barium chloride was prepared by dis found to produce BTO particles of spherical shape with a solving the salt of reagent grade (Katayama Chem. Co.) in narrow size distribution. Unfortunately, the DEO is spar- deionized water to give the nominal barium concentration in읺 y soluble in aqueous solution at room temperature and of 0.2 M. A stock solution of titanium tetrachloride of is not practical for BTO powder production.5 Later, present reagent grade (Yakuri Chem. Co.) was prepared by adding authors employed the thermal decomposition of dimethyl ox a 160 mL volume of the reagent slowly to a cold distilled alate (DM0) in nitrate ion systems as an alternative to DEO. water stirred rapidly and diluting to 1 L. The exact titanium Bull. Korean Chem. Soc. 1998, Vol. 19, No. 6 703 Notes content was determined gravimetrically by the hydroxide Table 1. Variation of generation rate for oxalate ions with vari precipitation method.78 The final solution was stored in a re ous experimental parameters for chloride system frigerator. rate to chloride Temperature [DMO]。 Cation stock solutions and the conjugate acidic solutions Run nucleation system (°C) of supporting anions were added to a beaker in predet no. ([Ba2+]0+[Ti4+]0) (min1) ermined quantities to adju아 the concentration ratio of 1 2 0.01 [Ba2+]o/[Ti4+]o to 1.00 along with a sufficient amount of dis 2 25 4 0.10 tilled water to bring the tot시 volume slightly less than 200 3 8 0.17 [cr]o=o mL. The beaker was covered and placed in an isothennal 4 2 0.16 (distilled bath that was set at the desired temperature. The predet 5 40 4 0.20 water) ermined amount of DM0 of reagent grade (Katayama 6 8 1.00 Chem. Co.) was added. The solution was brought exactly to 7 2 0.24 200 mL. The time to onset of precipitation, manifested as 8 50 4 0.50 the appearance of bluish tint, was recorded for each ex 9 8 1.50 periment and adopted as the critical nucleation time. 10 2 0.02 Small aliquots were collected and quenched to 0 °C at 11 25 4 0.03 regular time intervals to observe development of particle 12 8 0.05 morphologies and growth kinetics. The particles were sep- 13 2 0.07 [cr]o=o.i M erated from the supernatant liquid by centrifugation and 14 40 4 0.08 (0.1 M-HC1) washed twice with deionized water and twice with ethanol. 15 8 0.25 During the ethanol wash, particle옹 were dispersed with a 16 2 0.33 sonic disruptor. A drop of suspension in ethanol was placed 17 50 4 0.33 on an aluminium foil and dried for observation of BTO mor 18 8 0.50 phology by scanning electroscope (JEOL JSM 5800 LV). 19 2 0.58X10'2 A 5 mL of precipitated portions settled on the bottom of 1.54x10* 20 25 4 the beaker were also collected and quenched to 0 °C period 1.59X10* 21 8 ically to observe the overall morphology of the accumulated 22 2 1.08X10-2 [Cr]0=0.3 M precipitates at given aging times. 23 40 4 1.61X10-2 The whole precipitates settled on the bottom of the beak (0.3 M-HC1) 2.48x10“ 24 8 er at given aging times were quenched at 0 °C and were fi 25 2 1.54X10-2 nally seperated from the supernatant liquid by centrifugation, 2.22X10" 26 50 4 dried at 100 °C for 12 h and calcined at 900 °C for 2 h to 27 8 3.10X10-2 produce BT powders. Crystallinity and phase purity of the powders were determined by XRD (Rigaku, D/MAS-3C) us ing Ni-filtered Cu Ka radiation. results are similar to those for the fomation of ZnS pre Results and Discussion cipitates by homogeneous method.9 Table 1 also shows that the higher chloride concentrations In the present study, homogeneous precipitation is con are, the slower rates to nucleation are obtained, probably be trolled by the hydrolysis of DM0 to generate oxalate anions. cause of formation of more stable species. Below RN=2x 10* it usually took exceedingly long times for pre CH3O2CCO2CH3+2H2O — 2CH3OH+C2O42 +2H+ (1) cipitation to start (~50 min) and agglomerates of particles C2O42 +Ba2++Ti4+ -나 Ba-Ti-Oxalate (BTO) (2) were observed especially at relatively higher temperatures The oxalate concentration at any time t is a function of the and at longer aging times as shown in Table 1 and 2. combinations of experimental variables such as the initial However, depending on the relative value of RN above RN= concentrations of DMO, concentrations of barium and ti 2x 10"2 min1 and on aging times, either unimodal, bi- tanium ions, pH, temperature and concentration몽 of sup modal, or broad unimodal distributions of particle size were porting anions as described previously.5 This is equivalent observed. to saying that oxalate ion concentration increases with time Figure 1 아 lows a SEM micrograph taken at the aging t for a given combination of pH, temperature, and intial con time of 15-60 min after precipitation had started for run 2 centrations of DM0 and ions such as Ba2+, Ti4+ and sup (T=25 °C, ([Ba2+]o+[Ti4+]o)=O.O4 M, [Cr]=0.0 M, [DM이 ()/ porting anions. And the precipitates will appear at a critical ([Ba2+]0+ [Ti4+]0)=4) corresponding to a RN value of 0.10 nucleation time tc.

Load more