Citrate gel method

Various methods are applied to the synthesis of titania particles including sol-gel method, hydrothermal method [2], citrate gel method, flame processing and spray pyrolysis [1]. To utilize titania as a photocatalyst, the formation of ultrafme anatase titania particles with large crystallite size and large surface area by various ways has been studied [4]. 

Le et al. (2006) employed "amorphous citrate" gel method to prepare single phase ceramic powders of LaNiOs with controlled grain size by thermal annealing. The target product was obtained at 650 °C with particle sizes from 30 to 65 ran at annealing temperatures from 650 to 750 °C, while the crystalline sized varied from 10 to 15 ran. Accordingly, a wide... 

The citrate gel method involves the dissolving of solution of various nitrates in citric acid [257, 262,281-289]. Through controlling the pH values, no precipitate is in the solutions. After the solution is heated at a suitable temperature in air for a period of time, it becomes more and more viscous liquid containing polybasic... 

Batoo KM (2011) Stmctural and electrical properties of Cu doped NiFe204 nanoparticles prepared through modified citrate gel method. J Phys Chem Solids 72 1400-1407 Xie G-Q, Lu J-Q, Zheng H-Y, Liu X-J, Luo M-F, Li X-N (2010) Effect of carbonization temperature on the textural properties of Ceo.8Zro.2O2 solid solution by an improved citrate sol-gel method. J Alloy Compd 493 169-174... 

Soo MS, Joon YP, Byung JC (2003) Synthesis of yttrium aluminum garnet powder by citrate gel method. J Ceram Process Res 4 145-150... 

The citrate gel method was developed by Marcilly et al. (99) and can be illustrated by the synthesis of the ceramic superconductor YBa2Cu307 (100). Nitrate solutions of Y, Ba, and Cu were added to citric acid solution, and the pH was kept at 6 to prevent precipitation of barium nitrate. Heating the solution at 75°C in air produced a viscous liquid containing polybasic chelates. Further heating at 85°C in a vacuum produced an amorphous solid that was pyrolyzed in air at 900°C to produce a crystalline powder. 

Zayat Levy (2000) Zayat, M. Levy, D. Blue C0AI2O4 particles prepared by the sol-gel and citrate-gel methods Chemistry of Materials 12 9 (2000) 2763-2769 Zecchin (1990) Zecchin, L. II codice di Montpellier del 1536 recede per fare vetri colorati e smalti d ogni sorte havute in Murano Arsenale Ed., Venezia (1990)... 

Fig. 5.21 (a) Evolution of the lattice parameters vs. x(Li) in LLNii/3Mni/3Coi/302. Powders were prepared by citrate gel method with molar ratio Li/(Ni + Mn + Co)= 1. (b) Evoiution of the trigonal distortion, i.e., the cja ratio and particle size of Li Nii/3Mni/3Co]/302 powders as a function of the calcination time at the optimum temperature of 900 °C... 

Wang N, Zhang X, Bai Z, Sun H, Liu Q, Lu L et al (2011) Synthesis of nanociystalhne ytterbium-doped 5dtria by citrate-gel combustion method and fabrication of ceramic materials. Ceram Int 37 3133-3138... 

A citrate gel combustion method has been reported to synthesize nanosized ytterbium doped yttria [290]. Nanocrystalline powders single-phase... 

Maia AS, Stefani R, Kodaira CA, Eelinto MCFC, Teotonio EES, Brito HF (2008) Luminescent nanoparticles of MgAl204 Eu, Dy prepared by citrate sol-gel method. Opt Mater 31 440 44... 

Yu F, Yuan D, Cheng X, Duan X, Wang X, Kong L et al (2007) Preparation and characterization of yttrium gallium garnet nanoparticles by citrate sol-gel method at low temperature. Mater Lett 61 2322—2324... 

Kim KM, Ryu JH, Mhin SW, Park GS, Shim KB (2008) Luminescence of nanocrystalline Tb3Al50i2 Ce phosphors synthesized by nitrate-citrate gel combustion method. J Electrochem Soc 155 J293-J296... 

The groups of Song and Zhang et al. have used a combination of a sol-gel method and arrested precipitation to prepare nanocrystalline Y203-based upconverters [15,16]. They first prepared a gel from yttrium and lanthanide nitrates and ammonia hydroxide that was arrested by citrate ligands. Then, they calcinated the dried gel at 800°C and obtained upconverting nanocrystalline material. It has to be stated that methods that involve annealing/calcination always result in nanocrystalline material rather than colloidally stable nanoparticles. 

Citrate method is probably the most widespread and the most effective route to create high-surface-area perovskites (Figure 18.4) [23]. Additionally, the decomposition of the amorphous citrate precursors leads to mixed oxides or solid solutions of high homogeneity. Although often considered as a sol-gel method, citrate is a specific route. The comparison of the two mild chemical... 

The existence of a number of metal alkoxides suitable as sol-gel precursors for many oxide powders, such as silica or titanium oxide, and the compositional variability available are the main advantages of sol-gel procedures. However, for metal alkoxides with low valence, such as Fe, the hydrolysis and condensation are too rapid to control particle size and shape. Usually, magnetite and ferrites are preferably obtained by hydrolysis of metal salts such as acetates or citrates in water, ethanol, or glycol. The counterions work as a pH buffer and as a component of the precursor complexes. The conditions need to be chosen carefully to yield a material with appropriate properties for each specific application. Disadvantages of the sol-gel methods include contamination from reaction by-products, as well as the need for posttreatment of the products. 

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