Two methods used to synthesize high‐purity ferroelectric titanate powders in controlled, narrow size distributions, with average particle diameters <1000 A, were: (1) isothermal pyrolysis of barium titanyl oxalate or mixed calcium‐barium titanyl oxalates as low as 550° and 825°C, respectively, average particle sizes depending strongly on the pyrolysis temperature; and (2) hydrolysis of titanate esters in barium hydroxide. Using solvent media of controlled polarity, high‐purity stoichiometric BaTiO3 was obtained with average sizes as small as 100 A. Factors affecting stoichiometry and particle size are discussed in terms of assumed reaction mechanisms.

Inhibition of grain growth in pure, fine‐particle‐size barium titanate bodies by coating the surfaces of the barium titanate particles with tantalum oxide was so effective that doping with a sintering aid was necessary for densification of the bulk material at temperatures below the melting point. A correlation, which was independent of starting particle size, was established between inhibitor concentration and final grain size of the fired bodies. Barium titanate bodies of predetermined grain size not larger than 2000 A were obtained even with extended firing schedules. In the smallest grain sizes, the Curie point was shifted below the measured temperature range, and hysteresis losses were reduced markedly. The dielectric constant had a smooth variation from approximately 3000 at room temperature to 800 at 180°C.

The large change in the dielectric constant of barium titanate near 120°C was smoothed out by the use of very small particle sizes and additions of tantalum oxide. Unsupported thin sheets of the material showed the same electrical properties as thick pellets. Stacked capacitors made from these sheets, using platinum electrodes, showed a maximum capacitance change over the range 25° to 180°C of 19 to 27%, based on the room‐temperature value.

This report describes work done during the fourth quarterly contract period for the project *Ultra-Fine Particle Uise Ferroelectrics" which is directed to the preparation of controlled particle sizs polycrystalline dielectric film of ferroelectric materials; and also to theoretical studies NOEIZOuS OPO 4Nc|aATZ,

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