Synthesis of CaWO4, SrWO4 and BaWO4 with nanosized particles using cyclic microwave radiation

Scheelite tungstates (MWO(4), M = Ca, Sr and Ba) were successfully synthesized by the reactions of M(NO(3))(2) center dot 2H(2)O and Na(2)WO(4) center dot 2H(2)O in propylene glycol and NaOH using cyclic microwave radiation. The tungstates were detected using SAED. TEM and SEM analyses revealed the presence of dispersed nanosized particles for CaWO(4), nanosized particles in irregular clusters for SrWO(4), and nanosized particles in clusters shaped like dumb-bells for BaWO(4). Raman spectra provide evidence of the scheelite structure with six different vibration modes. Arrays of crystallographic planes were detected using HRTEM. PL emission of the products is caused by the (1)T(2) -> (1)A(1) transition of electrons within [WO(4)](2-) tetrahedrons in the blue spectral region at 407-419 nm.