The as-deposited (Nd_<1/3>Eu_<1/3>Gd_<1/3>)Ba_2Cu_3O_x (NEG123) films on MgO(100) substrates by metal organic deposition (MOD) method are amorphous and turns into crystalline when it is heated around 900℃. The growth mechanism of MOD is still not yet to understand. In this work, we report in situ observation of growth process of NEG123 films using a high temperature optical microscope. High temperature optical microscope clearly shows that (1) a larger amount of white particles appear at around 890℃, (2) NEG123 plate-like crystals with facet faces are formed in the white particles and (3) many NEG211 needle crystals are grown from flux (Ba and Cu rich particles) at a rate of about 7.5μm/sec.
