Mixed Hydroxide Precursors for La2Ti2O7 and Nd2Ti2O7 by Homogeneous Precipitation

• Published in: Journal of electroceramics 2001-04, Vol.6 (2), p.147-151
• Main Authors: Suresh, M, Prasadarao, A V, Komarneni, S
• Format: Article
• Language: English
• Subjects: Hydroxides; Neodymium; Oxalates; Precipitation; Precursors; Titanium; Titanium dioxide
• ISSN: 1385-3449; 1573-8663
• DOI: 10.1023/A:1011464902626

Feasibility of formation of stoichiometric precursors of either M^sub 2^ (TiO)^sub 2^(C^sub 2^O^sub 4^)^sub 5^ 4H^sub 2^O (M = La and Nd) or coprecipitated hydroxides of M(OH)^sub 3^+TiO(OH)^sub 2^ was investigated by two solution routes at different pH values. Composition of precipitates obtained at pH = 7.0 by coprecipitation method starting from La or Nd nitrates and potassium titanyl oxalate corresponded to a physical mixture of La or Nd(C^sub 2^O^sub 4^)^sub 3^ 9.5H^sub 2^O and TiO(OH)^sub 2^7·H^sub 2^O which on thermal decomposition did not yield phase pure M^sub 2^Ti^sub 2^O^sub 7^. However, precipitation from La or Nd nitrates and titanium tertrachloride by urea hydrolysis yielded homogeneous mixture of hydroxides of La or Nd and Ti, which on pyrolysis at 950°C yielded phase pure La^sub 2^Ti^sub 2^O^sub 7^ and Nd^sub 2^Ti^sub 2^O^sub 7^. Use of potassium titanyl oxalate as precursor for Ti, led to selective precipitation of La or Nd oxalate even at pH as low as 0.1 leading to sequential precipitation of La or Nd oxalate followed by Ti hydroxide at pH = 3.0. The resultant precipitate on pyrolysis underwent typical solid-state reaction.[PUBLICATION ABSTRACT]