Li_2O-WO_3系化合物の合成と高温蒸発

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Syntheses, sinterings and vaporizations of double oxides of Li_2O・WO_3(1/1), 2Li_2O・WO_3(2/1) and 3Li_2O・WO_3(3/1) in the system Li_2O-WO_3 were investigated. 1/1 mixture changed to 3/2 compound at 100℃ and 1/1 formed above 500℃. Sinterings of 1/1 were made at 700℃ for 4h with relative density(RD) of 89-91%. 2/1 mixture changed to α-2/1 from 100 to 700℃ and β-2/1 appeared in the temperature range from 740 to 1000℃. Sinterings were made at 800 to 1000℃ with RD of 45-47%. 3/1 mixture began to form 3/1 at 600-700℃ and maximum yield of 3/1 compound was obtained at 1000℃. Sinterings were made at 900-950℃ for 3h with RD of 62-80%. Vaporization experiments on pellets (1.37 cm in dia.) were made in air flow (1 cm・min^<-1>) at temperatures from 700 to 1000℃, and straight lines with slopes from 0.2 to 1.0 were obtained on a log-log graph of both vaporization and time. These slope values increased approaching to 1 with increasing vaporization time. From the vaporization rates at early stages, an activation energy of 170 kJ・mol^<-1> was obtained for 3/1 compound. Products after the vaporizations of 3/1 compound were mixtures of 2/1 and 3/1. The vaporization experiments for pure WO_3 were also made at 700-1100℃ and the slope values were almost 1. The amount of vaporization was lower than those for 3/1 and 2/1. Effect of porosity on the vaporization was confirmed using NaCl compacts with various porosities. The maximum increase of the vaporization rate against the specimen with 0% porosity was 14% for that with 30% porosity.
社団法人日本セラミックス協会の論文
1996-10-01

Li_2O-WO_3系化合物の合成と高温蒸発

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