Rapid synthesis of Y- And BI-based high-T_C cuprates by microwave irradiation

High-T_c superconducting samples of YBa₂CU₃O_7-x with T_c∼90 K and Bi_2.2Sr_1.8Cu_1.05O_x with T_c∼9 K have been prepared for several ten min, using a domestic microwave oven operated at 2.45 GHz, without any post-heat-treatment. Post-heat-treatment is not necessary due to improvement of the sample environment during the microwave process. That is, a pellet of mixed powder of starting materials is surrounded by mixed powder of starting materials and, subsequently, wrapped in glass wool in order to suppress rapid dissipation of heat from the surface of the pellet. This leads to successful preparation of homogeneous and oxygenated samples. In addition, we have attempted to prepare Bi-2212 and Bi-2223 phases. A sample whose major phase was Bi-2212 was obtained. However, no sample with the Bi-2223 phase could be obtained.