Structure study of MoO3–ZnO–B2O3 glasses by Raman spectroscopy and formation of α-ZnMoO4 nanocrystals

Molybdenum oxide (MoO3)-containing glasses of xMoO3–50ZnO–(50−x)B2O3 (x = 10, 20, and 30) are prepared using a conventional melt quenching method, and the glass structure and crystallization behaviour are clarified. It is found that the thermal stability against crystallization of the glasses decreases drastically with increasing MoO3 content. The main valence of Mo ions in the glasses is found to be Mo6+ from X-ray photoelectron spectroscopy measurements. The Raman bands observed at ∼860 cm−1 and 950 cm−1 suggest that the coordination state of Mo6+ ions in the glasses is mainly (MoO4)2− tetrahedral units. All glasses examined in this study give the formation of α-ZnMoO4 as the initial crystalline phase. In particular, 30MoO3–50ZnO–20B2O3 glass shows the bulk crystallization of α-ZnMoO4 nanocrystals with a diameter of ∼5 nm. The crystallized glasses consisting of Eu3+-doped ZnMoO4 crystals are synthesized, and enhanced photoluminescence emissions (i.e., the quantum yield is 9%) due to the 4f transitions 5D0 → 7FJ (J = 0–4) of Eu3+ ions is observed.

Research highlights
► Structure and crystallization behavior of molybdenum zinc borate glasses are examined.
► The Raman bands suggest that the coordination state of Mo6+ ions in the glasses is mainly (MoO4)2− tetrahedral units.
► α-ZnMoO4 nanocrystals with a diameter of ∼5 nm are formed.
► The crystallized glasses consisting of Eu3+-doped ZnMoO4 crystals show photoluminescence emissions of the quantum yield 9%.