Supersonic microwave co-assistance (SMC) efficient synthesis of red luminescent Eu3+ activated silver molybdates and their phase-dependent evolution processes

Abstract

The chemical effects of high intensity ultrasound and microwave irradiation on the preparation of europium(III) activated silver molybdates were investigated and characteristic red emission was successfully achieved at a very low temperature (70 °C) in 40 minutes. X-ray powder diffraction results proved that the crystal phase of silver molybdate was heavily related to the pH value. Scanning electron microscopic images revealed rod-like structures of Ag₂Mo₃O₁₀·1.8H₂O and Ag₂Mo₂O₇ were obtained in the range of pH values between 2 and 5, while growing particles of Ag₂MoO₄ were formed at pH values of 7 and 8. Furthermore, it has been found that the encapsulation of europium(III) in monoclinic crystal structure (Ag₂Mo₂O₇) resulted in enhanced luminescence intensities compared to other crystal phases.