A method of preparing a superconductor. The method includes preparing a mixture of superconductor material constituents, disposing the constituents on a silver containing substrate, heating the mixture of constituents on a silver containing substrate, heating the mixture in a first atmosphere having a partial pressure of CO2 to control decomposition of at least one of the superconductor material constituents and changing the first atmosphere to a second atmosphere consisting essentially of an oxidizing gas capable of allowing decomposition of at least one of the superconductor material constituents.