The simplest method for preparing ceramic superconductors is a solid-state thermochemical reaction involving mixing, calcination and sintering. The appropriate amounts of precursor powders, usually oxides and carbonates, are mixed thoroughly using a Ball mill. Solution chemistry processes such as coprecipitation, freeze-drying and sol–gel methods are alternative ways for preparing a homogeneous mixture. These powders are calcined in the temperature range from 1,070 to 1,220 K (800 to 950 °C) for several hours. The powders are cooled, reground and calcined again. This process is repeated several times to get homogeneous material. The powders are subsequently compacted to pellets and sintered. The sintering environment such as temperature, annealing time, atmosphere and cooling rate play a very important role in getting good high- T c superconducting materials. The YBa 2 Cu 3 O 7− x compound is prepared by calcination and sintering of a homogeneous mixture of Y 2 O 3, BaCO 3 and CuO in the appropriate atomic ratio. Calcination is done at 1,070 to 1,220 K (800 to 950 °C), whereas sintering is done at 1,220 K (950 °C) in an oxygen atmosphere. The oxygen stoichiometry in this material is very crucial for obtaining a superconducting YBa 2 Cu 3 O 7− x compound. At the time of sintering, the semiconducting tetragonal YBa 2 Cu 3 O 6 compound is formed, which, on slow cooling in oxygen atmosphere, turns into superconducting YBa 2 Cu 3 O 7− x. The uptake and loss of oxygen are reversible in YBa 2 Cu 3 O 7 −x. A fully oxygenated orthorhombic YBa 2 Cu 3 O 7− x sample can be transformed into tetragonal YBa 2 Cu 3 O 6 by heating in a vacuum at temperature above 973 K (700 °C).