36 «“√ “√«‘®—¬ ¡¢. (∫».) 7 (1) : ¡.§. - ¡’.§. 2550 A Novel Route to Synthesis of Lead Glycolate and Perovskite Lead Titanate, Lead Zirconate, and Lead Zirconate Titanate (PZT) via Sol-Gel Process π«—µ°√√¡¢Õß°√–∫«π°“√ —߇§√“–Àå‡≈¥‰°≈‚§‡≈µ·≈–‚§√ß √â“ß·∫∫ ‡æÕ√Õø ‰°µå¢Õ߇≈¥‰∑∑“‡πµ ‡≈¥‡´Õ√傧‡πµ ·≈– ‡≈¥‡´Õ√傧‡πµ‰∑∑“‡πµ ºà“π°√–∫«π°“√‚´≈-‡®≈ Nuchnapa Tangboriboon (πÿ™π¿“ µ—Èß∫√‘∫Ÿ√≥å)* Dr. Sujitra Wongkasemjit (¥√. ÿ®‘µ√“ «ß»å‡°…¡®‘µµå)** Dr. Alexander M. Jameison (¥√. Õ‡≈Á°´“π‡¥Õ√å ‡ÕÁ¡ ‡®¡‘ —π)*** Dr. Anuvat Sirivat (¥√. Õπÿ«—≤πå »‘√‘«—≤πå)**** ABSTRACT The reaction of lead acetate trihydrate Pb(CH3COO)2.3H2O and ethylene glycol, using triethylenetetramine (TETA) as a catalyst, provides, in one step, an access to a polymer-like precursor of lead glycolate [-PbOCH2CH2O-] via oxide one pot synthesis (OOPS). The lead glycolate precursor has superior electrical properties than lead acetate trihydrate, suggesting that the lead glycolate precursor can possibly be used as a starting material mixed with other precursors such as titanium glycolate and sodium tris (glycozirconate) to produce lead titanate, lead zirconate, and lead zirconate titanate by sol-gel transition process. ∫∑§¥¬— àÕ ß“π«‘®—¬π’ȉ¥â»÷°…“°“√‡°‘¥ªØ‘°‘√‘¬“√–À«à“߇≈¥Õ–´’‡µ¥‰µ√‰Œ‡¥√µ ·≈–‡Õ∑‘≈’π‰°≈§Õ≈‚¥¬„™â “√ ‰µ√‡Õ∑‘≈’π‡µµ√–¡’π‡ªìπ§–µ–≈’ µå‡æ◊ËÕ„™â„π°“√º≈‘µ “√µ—Èßµâπ‚æ≈‘‡¡Õ√å§◊Õ‡≈¥‰°≈‚§‡≈µ [-PbOCH2CH2O-] ∑ ”§’Ë ≠™π— ¥Àπ‘ ßµ÷Ë Õ¢∫«π°“√𔉪„™à „π°“√ â ߇§√“–À— å “√‰¥Õ‡≈§µ√‘ °™π‘ ¥µ‘ “ßÊà ‰¥·°â à “√‡øÕ√‚√‰¥Õå ‡≈§µ√‘ °‘ “√·Õπ‰∑‡øÕ√å‚√Õ‘‡≈§µ√‘°·≈– “√‡æ’¬‚´‰¥Õ‘‡≈§µ√‘°®“°°“√ —߇§√“–Àå¥â«¬ “√ª√–°Õ∫ÕÕ°‰´¥å‡æ’¬ß ¢—ÈπµÕπ‡¥’¬«∑’ˇ√’¬°«à“ Oxide One Pot Synthesis (OOPS) ∑”„À≥⠓√µ—Èßµâπ‡≈¥‰°≈‚§‡≈µ¡’ ¡∫—µ‘∑“߉øøÑ“ ¥’°«à“‡≈¥Õ–´’‡µ¥‰µ√‰Œ‡¥√µ πÕ°®“°π’Ȭ—ß “¡“√∂𔉪„™âº ¡°—∫ “√µ—Èßµâπ™π‘¥Õ◊ËπÊ ‡™àπ ‰∑∑“‡π’¬¡ ‰°≈‚§‡≈µ·≈–‚´‡¥’¬¡∑√’ ‰°≈‚§‡´Õ√傧‡πµ‡æ◊ËÕº≈‘µ‡≈¥‰∑∑“‡πµ ‡≈¥‡´Õ√傧‡πµ·≈–‡≈¥‡´Õ√傧‡πµ ‰∑∑“‡πµ ‚¥¬ºà“π°√–∫«π°“√‚´≈-‡®≈∑√“π ‘™—Ëπ Key Words : OOPS, Sol-gel process, Dielectric materials §” ”§—≠ : OOPS °√–∫«π°“√‚´≈-‡®≈ «— ¥ÿ‰¥Õ‘‡≈§µ√‘° * Ph.D. of Petroleum and Petrochemical College, Chulalongkorn University, Bangkok, Thailand 10330 ** Assoc. Prof., Petroleum and Petrochemical College, Chulalongkorn University, Bangkok, Thailand 10330 *** Prof., The Macromolecule Science Department, Case Western Reserve university, Cleveland, Ohio, USA. **** Assoc. Prof., Petroleum and Petrochemical College, Chulalongkorn University, Bangkok, Thailand 10330 KKU Res J (GS) 7 (1) : January - March 2007 37 Introduction high purity, but they are expensive and extremely The semiconducting materials, such as moisture sensitive (Brinker et al., 1990). ferroelectrics, antiferroelectrics, superconductor and Ferroelectric crystals necessarily possess piezoelectric products, show great potentials for using both pyroelectric and piezoelectric properties. as sensors, actuators, transducers, electro-optic Many lose these polar properties at the transition or devices, thermistors, microelectro mechanical the Curie temperature Tc. A nonpolar phase above system (MEMS) applications (micromotors, Tc is called paraelectric phase. Lead titanate and microvalves, micropumps), PTC (positive lead zirconate titanate are kinds of ferroelectric temperature coefficient), acoustic transducer, materials which have electric dipole moment which binary ferroelectric memory, resistors and can be spontaneously polarized with reversibility capacitors because of their good properties on [1,4-7]. Furthermore, ferroelectric can be used as dielectricity, pyroelectricity and piezoelectricity biosensor such as piezo-sensing devices and (Fang et al,1999; Lobmann et al.,1995; Paris biosensors for urea, glucose, DNA, immune et al., 1998; YXL, 1993). The most common and cholesterol (Brinker et al., 1990). Lead zirconate well-known electrical and semiconducting ceramic is an antiferroelectric material having a non-permanent electric dipole moment whose materials are lead titanate (PbTiO3), lead zirconate complete or partial realignment can be reversible (PbZrO3), lead zirconate titanate (PZT or under appropriate conditions. Lead zirconate can Pb(Zr,Ti)O3) and lead/lanthanum zirconate show a phase switching from the antiferroelectric titanate (PLZT or (Pb,La) (Zr,Ti)O3). Many processes to produce these semiconducting phase to the ferroelectric phase by applying electric ceramic materials include the sol-gel method, field or raising temperature. The methods required the chemical co-precipitation, the hydrother mal for the synthesis of alkoxy derivatives of an synthesis, the traditional solid state reaction of mixed element generally depend on its electronegativity oxides, the molten salt preparation, the solvothermal and electron configuration. The chelating nature of synthesis, the emulsion technique, and the complex the glycol and the coordinative saturation achieved polymerization (YXL, 1993; Fang et al., 2002; by the central atoms in the final products appear to Hermandez et al., 2002; Bersani et al., 1995; be the main factor for their hydrolytic stability to Gurkovich et al., 1982; Palchik et al, 2000). retard the hydrolysis and condensation reaction rates The sol-gel process has an advantage over others in order to form homogeneous gels rather than in producing various shapes during the gel-state precipitates (Kakihana et al., 1997). Other work at low processing temperatures, e.g., monoliths, reported metalloglycolates formed from alkaline films, fibers and monosized powders along with glycol such as aluminium, silicon, titanium, and compositional and microstructural controls (Brinker magnesium-aluminium (Yang et al., 2001; et al.., 1990). For conventional processes of Day et al., 1996; Brinker et al., 1986). producing semiconducting ceramics, the starting raw Specifically, (Archer et al., 1996) studied the role materials from metal alkoxide precursors require very of precursor segregation in the formation of the 38 «“√ “√«‘®—¬ ¡¢. (∫».) 7 (1) : ¡.§. - ¡’.§. 2550 perovskite phase PbTiO3 using either lead oxy Company Limited (TIG). Lead acetate trihydrate glycolate Pb(OCH2CH2O)2 or lead phenoxy Pb(CH3COO)2 .3H2O containing 99.5% purity was glycolate compounds. The lead precursors were purchased from Asia Pacific Specialty Chemical synthesized by refluxing the lead carbonate with Limited (Australia) and used as received. Titanium an appropriate carboxylic acid in water. dioxide was purchased from Sigma-Aldrich From previous studies, the sol-gel Chemical Co., Ltd. (USA). Zirconium (IV) process appears to be the mildest method to hydroxide Zr(OH)4 containing 88.8% ZrO2 was produce lead titanate, lead zirconate, lead zirconate purchased from Aldrich Chemical Co., Inc. (USA). titanate. In an all-alkoxide sol-gel process, Ethylene glycol (EG) was purchased from alkoxides of the constituent elements show Farmitalia Carlo Erba (Barcelona) or Malinckrodt different reactivities toward water so that the Baker, Inc. (USA). Triethylenetetramine (TETA) preparation of multicomponent homogeneous was purchased from Facai Polytech. Co., Ltd. systems is difficult. The high cost of the alkoxide (Thailand) and distilled under vacuum (0.1 mm/ reagents and the need to work under inert Hg) at 130 ÌC prior to use. Acetonitrile was atmospheres are major disadvantages of this purchased from Lab-Scan Co., Ltd. system. Inorganic and organic salts have also been The starting raw materials, lead glycolate, used for the sol-gel processing of multicomponent titanium glycolate and sodium tris (glycozirconate) systems when the use of constituent alkoxides were synthesized by the oxide one pot synthesis become difficult or unnecessary. Many researches process (OOPS) which was less moisture sensitive. by Wongkasemjit et al., group reports have Precursor Synthesis demonstrated that using the Oxide One Pot Lead Glycolate [16] Synthesis (OOPS) process, moisture stable metal Lead glycolate was synthesized via the alkoxides can be successfully synthesized. OOPS process. A mixture of lead acetate trihydrate Therefore, the aim of this study is to synthesize (Pb(CH3COO)2.3H2O, 0.1 mol, 37.9 g), high purity lead titanate, lead zirconate and lead ethylene glycol (EG, 0.1 mol, added excess 50 zirconate titanate (PZT) via the sol-gel process using cm3) and triethylenetetramine (TETA, 0.1 mol, lead glycolate, titanium glycolate and sodium tris 14.6 g) acted as a catalyst when heated at the (glycozirconate) precursors from the OOPS boiling point of EG under N2 in a thermostated oil process. We also investigate the influence of bath. The excess EG was slowly distilled off as to calcination temperature and time on physical and remove water liberated from reaction. After heating chemical properties; i.e., morphology, phase at 200 ÌC for 1 h, the solution color changed to be transformation, and electrical properties. yellow or golden brown. The reaction mixture was cooled to obtain a crude precipitate product Experiment followed by filtration with acetonitrile. The light Materials bronze solid product was obtained and dried in UHP grade nitrogen, 99.99% purity, was a vacuum dessicator (0.1 mm Hg) at room obtained from Thai Industrial Gases Public temperature and characterized using FTIR, KKU Res J (GS) 7 (1) : January - March 2007 39 13C-NMR,FAB+-MS, TGA, pycnometer and removed by the vacuum distillation to obtain a crude Impedance Analyzer. precipitate. The white solid product was washed with acetonitrile and dried in a vacuum dessicator before characterization using FTIR, TGA. FTIR bands observed were: 2778-2829 cm-1 correspond ing to the C-H stretching of ethylene glycol bidentate ligand, 1086