Low-Temperature Synthesis of Monazite-Type Lanthanum
Orthovanadate (LaVO4) from Aqueous Solution
Keiji DAIMON*, Wu MIN, Yasuo HIKICHI, Naoto WADA, Takashi MATSUBARA and Toshitaka OTA
Department of Materials Science and Engineering, Nagoya Institute of Technology; Gokiso-cho, Showa-ku, Nagoya-shi 466-8555 Japan
Monazite-type monoclinic form lanthanum orthovanadate (M-type LaVO4) was synthesized by precipitating it from the mixed solution of lanthanum chloride and ammonium vanadate (V) with the mixing atomic ratio (La/V)=1 at 20 °C in the pH 5 to 9. However, M-type LaVO4 tended to coexist with zircon-type tetragonal form lanthanum orthovanadate (Z-type LaVO4) at pHs 5-8. The single phase M-type LaVO4 was obtained only pH 9. The La/V atomic ratio obtained from the chemical analysis (ICP method) was in the range 0.99-1.01. The specific surface area and crystallite size were 250 m2/g and 22 nm, respectively. Relative density larger than 95% was achieved when the green compacts of M-LaVO4 were sintered at 1500 °C for 3 h in air.