Na2S and Na2S2 were selectively synthesized using a microwave-assisted thermal treatment of a Na+/S solution in tetraglyme between 100 and 200 degrees C, considerably lower than that of current routes. This novel synthetic pathway yields the Na2S phase in high purity and allows for good selectivity between the polymorphs of Na2S2 (alpha and beta phases). These materials show promising electrochemical properties and are particularly interesting for the continued development of Na-S batteries.