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In this article, the synthesis by means spray pyrolysis method, of the CaMoO4 and rare earth cation (RE 3+)-doped CaMoO4:xRE 3+ (RE 3+ = Eu 3+ , Tb 3+ , and Tm 3+ ; and x= 1%, 2%, and 4% mol) compounds is presented. The as-synthesized samples were characterized using x-ray diffraction (XRD), Rietveld refinement, field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, and photoluminescence (PL) spectroscopy. To complement and rationalize the experimental results, first principle calculation, at density functional theory level, have been performed to analyze the band structure and density of states. In addition, a theoretical method based on the calculations of surface energies and Wulff construction was applied to obtain the morphology transformation of the CaMoO4 and CaMoO4:RE 3+ microstructures. The experimental morphologies can be observed in the FE-SEM images. The PL behavior of the co-doped samples exhibited well-defined bands in the visible region. The samples with 2% and 4% of RE 3+ released white emission according to the chromaticity coordinates (0.34, 0.34) and (0.34, 0.33), respectively. Present results provide not only a deep understanding of the structure-property relationships of CaMoO4-based phosphor, but also can be employed as a guideline for the design of the electronic structure of the materials and the fabrication of photo-functional materials with optimal properties, which allows for the modeling of new phosphors for applications in solid-state lighting.

behavior and structural properties with various practical applications in different fields that involve chemical and biological applications, sensor and detector, display devices, light emitting diodes (LEDs), optical fibers, scintillator materials, catalysis and lithium ion batteries [1-3]. Among these compounds, calcium molybdate, CaMoO 4 , is one of the most attractive members of this family due to its very interesting physical and chemical properties as well as electronic structure, their high luminescence intensity, good thermal and chemical stability and high density. These properties allow it to be a good host material for luminescent materials under ultraviolet (UV) and X-ray excitation [2,[4][5][6][7][8][9][10][11][12][13][14][15].CaMoO 4 presents a body-centered scheelite structure, which belongs to the tetragonal I4 1 /a space group and contains two formula units per primitive cell. In this crystal, the building blocks of this structure are the (MoO 4 ) and (CaO 8 ) clusters corresponding to the local coordination in which Mo cation is linked to four equivalent O anions to construct (MoO 4 ) tetrahedral clusters while the Ca cation forms (CaO 8 ) octahedral clusters and it shares corners with eight adjacent O anions in (MoO 4 ) tetrahedrons. In turn, (CaO 8 ) octahedral connect via its edges and form a 3D framework [16,17]. In particular, the optical behavior of CaMoO 4 is associated to the stability and luminescent properties of (MoO 4 ) tetrahedron cluster with strong absorption in the UV region due to the charge transfer from oxygen to metal.A plethora of synthetic routes was successfully used to obtain CaMoO 4 including the flux method. It has also been employed the Czochralski technique, floating zone-like technique, microemulsion process, citrate complex method, co-precipitation method, electrospinning process, chemical deposition, hydrothermal/solvo thermal routines, and microwave assisted techniques [7,13,[18][19][20][21][22][23][24][25][26][27][28][29][30][31].

The PbMoO 4 co-doped with Tm 3þ , Tb 3þ Eu 3þ with scheelita structure was synthesized by the sonochemical method. The photoluminescent properties, structural and color coordinates emitted by phosphors were investigated. The structural analysis of the crystal and the changes in lattice parameters confirm that the rare earth ions (RE 3þ) were successfully introduced into the host of the PbMoO 4. The relationship between energy gap (Egap) and the concentration of RE 3þ ions was also discussed, the Egap is significantly influenced by the degree of structural order-disorder present in the crystal lattice. The PbMoO 4 :RE 3þ shows light emission in green. Under UV excitation, Photoluminescence (PL) shows a broad band centered at 520 nm and smaller bands belonging to transitions of RE 3þ :

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