Novel approach for the bulk synthesis of nanocrystalline yttria doped thoria powders via polymeric precursor routes

Three different polymeric precursor routes viz., (i) amorphous citrate process, (ii) Pechini process and (iii) polyethylene glycol assisted process were compared for synthesising nanocrystalline powders of 7.5 mol% yttria doped thoria (YDT). In each of the processes, parameters such as metal-to-fuel ratio or composition of fuel were varied and the effects were analysed. TG/DTA studies were conducted to identify the ignition temperatures of the precursors. Also, a novel experimental procedure with controlled combustion was devised for the preparation of powders based on the thermal analysis data. All the processes result in phase pure and nanocrystalline powders. The average crystallite size of the powders ranged between 9 and 18 nm. The powder samples were analysed for their carbon content and studied for their sinterability. Densities as high as 99% th.d. could be achieved by sintering the compacts of powders obtained from (i) amorphous citrate process with CA/M ratios 2.0 and 3.0, (ii) Pechini processes (independent of fuel composition) and (iii) PEG-assisted process using PEG 4000 at a relatively low temperature of 1500 °C for 2 h.

[1]  S. Anthonysamy,et al.  PVA aided microwave synthesis: A novel route for the production of nanocrystalline thoria powder , 1996 .

[2]  B. Bugbee,et al.  Electrochemical oxygen sensor for measurement of oxygen in liquid sodium , 1978 .

[3]  E. Subbarao,et al.  Defect Structure and Electrical Conductivity of ThO2‐Y2O3 Solid Solutions , 1965 .

[4]  Seung-Bin Park,et al.  Preparation of lithium aluminate via polymeric precursor routes , 1998 .

[5]  L. Alexander,et al.  X-Ray diffraction procedures for polycrystalline and amorphous materials , 1974 .

[6]  I. Cosentino,et al.  Powder synthesis and sintering of high density thoria–yttria ceramics , 2002 .

[7]  S. Anthonysamy,et al.  Combustion synthesis of thoria – a feasibility study , 1999 .

[8]  A. K. Tyagi,et al.  Nanocrystalline thoria powders via glycine-nitrate combustion , 2001 .

[9]  K. W. Bagnall.  The actinide elements , 1973 .

[10]  R. G. Taylor,et al.  Testing and performance of electrolytic oxygen meters for use in liquid sodium , 1983 .

[11]  J. N. Pratt.  Applications of solid electrolytes in thermodynamic studies of materials: A review , 1990 .

[12]  A. Pathak,et al.  Low-temperature preparation of fine particles of mixed oxide systems , 1995 .

[13]  E. Subbarao,et al.  Electrical conductivity of pure and CaO-doped ThO2 ceramics , 1973 .

[14]  M. Kolodney,et al.  DEVELOPMENT OF A CONTINUOUS ELECTROCHEMICAL METER FOR OXYGEN IN SODIUM. , 1967 .

[15]  M. Pisárčik,et al.  Microstructure and physical properties of transparent thoria-yttria ceramics , 1991, Journal of Materials Science.

[16]  K. Nagaraja,et al.  Preparation of 15 mol% YO1.5-doped ThO2 disk electrolytes by a polymeric gel-combustion method , 2001 .

[17]  I. Cosentino,et al.  Properties of thoria-yttria solid electrolytes prepared by the citrate technique , 1997 .

[18]  C. P. Smith,et al.  Electrochemical techniques for monitoring dissolved carbon, hydrogen and oxygen in liquid sodium , 1982 .