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3093273 
Journal Article 
Influence of pH on the property of apatite-type lanthanum silicates prepared by sol-gel process 
Shi Qingle; Lu Lihua; Zeng Yanwei; Zhang Hua 
2012 
1 
Journal of Wuhan University of Technology--Materials Science Edition
ISSN: 1000-2413
EISSN: 1993-0437 
27 
5 
841-846 
WOS:000310473400007 
The apatite-type lanthanum silicates with formula La9.33Si6O26 are prepared by sol-gel process. The homogeneity of the sol affected by pH value of the solution is investigated. The viscosity of the sols slightly increases first and then increases abruptly because the predominant reaction mechanism changes from hydrolysis reaction to condensation reaction. In addition, the onset time of the increase for the viscosity shortens from pH 1 to pH 4. The gelation time decreases with increasing pH of the solution. Therefore, the pH of the sols should be less than 4 to form gel. The sol with initial pH 2 shows maximum value of zeta potential and maximum stability. For the sample with initial pH 2, pure apatite-type lanthanum silicates La9.33Si6O26 have been successfully prepared after the dried gel is calcined at 1 000 A degrees C. In addition, this sample sintered at 1 550 A degrees C exhibits the highest ionic conductivity. The activation energies are all less than 0.90 eV. 
sol-gel process; pH; X-ray diffraction; ionic conductivity