TETRA-ORTHO TRANSITION AND TEMPERATURE-DEPENDENCE OF THE LONDON PENETRATION DEPTH IN SUBMICRON YBACUO PARTICLES PREPARED BY A SOL-GEL TECHNIQUE

Magnetization measurements of submicron YBa2Cu3O6+x particles, obtaine d by sol-gel technique, is presented. The 123-single phase grains afte r t(s) = 5 hours of synthesis at low (850 degrees C) temperature appea rs to be tetragonal and nonsuperconducting even at x = 0.82. For t(s) > 10 h diamagnetic response is well fitted by lambda(T) = lambda(0). [ 1 - (T/T-c)(n)](-1/2) at n = 1 while for sample prepared at 900 degree s C (12 h) more conventional exponent n = 2 is obtained.