Preparation of CaTiO3 porous substrate by foam-burning method

CaTiO3 porous substrates required for spin-coating of mixed conductor Ca(Ti, Fe)O-3 films were prepared by a foam-burning method. Mixtures of calcined CaTiO3 powder and foaming agents such as corn starch, wheat starch D(+)-glucose and carbon black were heated gradually up to 500 degrees C, then kept at 500 degrees C for 2 h and finally sintered at 1350 degrees C. Relatively large pores above 15 mu m in diameter were formed when 15-35 mass% corn starch was used as a foaming agent. Pore diameter distribution broadened with wheat starch. Sintered compacts with pore diameters as small as 5-10 mu m were prepared by using 15-25 mass% carbon black or D(+)glucose. The addition increased the mechanical properties of the spin-coated substrate. Gas permeability was found to increase according to the order; corn starch > wheat starch > D (+)-glucose greater than or equal to carbon black for a fixed amount of addition. An accelerated increase in the gaseous permeability was ascertained with increasing amount of foaming agent. A CaTiO3 porous substrate prepared with 20 mass% carbon black or 40 mass% wheat starch exhibited sufficiently high mechanical strength for the thermal cyclic process of spin-coating and subsequent sintering.