Blocky and spheroidal growth in Y1.5Ba2Cu3Ox system

Solidification of Y1.5Ba2Cu3Ox system was studied with the aim to find the temperature of self-nucleation. The microstructure after cooling from isothermal dwells in the temperature range 984–995 °C was analysed. It is shown that blocky YBa2Cu3O7−δ crystals were self-nucleated and grown during isothermal dwells below 988 °C and spheroidal multicrystals were formed during cooling from isothermal dwells at higher temperatures. The symmetrical and radial YBa2Cu3O7−δ crystal branches of spheroids grow in the 〈110〉 crystal direction.

► Temperature of selfnucleation in Y1.5Ba2Cu3Ox determined by microstructural analyses.
► Spheroidal solidification at cooling from temperature above selfnucleation.
► Spheroid branches grow in the 〈110〉 crystal direction.