The Synthesis And High-pressure Studies Of Eu³⁺:SrMoO₄

Metal molybdates?AMoO₄?and tungstates?AWO4?of relatively large bivalent cations?ionic radius?29?0.99 ?;A=Ca,Ba,Sr,Pb or Eu?crystallize in the so-called scheelite structure,which belongs to the tetragonal space group?SG?I41/a.SrMoO₄ crystallizes in the so-called scheelite structure,which belongs to the tetragonal space group?SG?,the unit-cell parameters are: a=b=0.5394?,c=1.202?.Doped molybdates possess good thermal stability and chemical properties,and has been widely used as optical fiber,scintillator,sensor,photoluminescence,catalyst,which is important photoelectric industry material and excellent luminescent substrate material.Many research groups have studied the doped molybdates,but most of the researches focused on the bulk material for high pressure research,the preparation of a variety of morphologies of doped molybdate and the physical properties under ambient pressure.The inquiry of nano or micron scale of various morphologies for high pressure is still a vacancy.In this study,we synthesized two kinds of Eu³⁺: SrMoO₄ materials using chemical and ultrasonic method by controlling the influence condition-PH value.The synthesized samples were characterized by X-ray diffraction spectrometer,scanning electron microscope,and transmission electron microscope.The high pressure behaviors of the as-synthesized sample were investigated by in situ high-pressure synchrotrion angle-dispersive X-ray diffraction,in situ high-pressure Raman scattering,and in situ high-pressure fluorescence measurements in diamond anvil cells at room temperature.The details are as follows:1.Eu³⁺: SrMoO₄ materials were synthesized through a simple and convenient chemical method by changing the influencing factors-p H value.The synthesized samples were characterized by various methods,such as XRD?SEM?TEM?HRTEM?DIFF.2.The high pressure behaviors of the as-synthesized Eu³⁺: SrMoO₄ nanometer material were investigated by in situ high-pressure synchrotrion angle-dispersive X-ray diffraction,in situ high-pressure Raman scattering,and in situ high-pressure fluorescence measurements in diamond anvil cells at room temperature.A phase transition was observed from the scheelite-structured ambient phase?space group I41/a?to a monoclinic fergusonite phase?space group I2/a?at 11.34 GPa.On release of pressure the initial phase is recovered,implying that the observed structural modifications are reversible.The transition pressure is considerably lower than that of bulk SrMoO₄,which is caused by the incorporation of Eu³⁺.The diffraction peak corresponding to the crystal plane?2 0 0?moves to the low angle at the phase transition,which indicates that the a axis of the crystal structure does not shorten with the increasing of pressure but has a tendency of elongation.As in other scheelite-structured molybdates and tungstates,the compression of Eu³⁺: SrMoO₄ nanometer material is highly anisotropic,the c-axis being more compressible than the a-axis,which is mainly due to the crystal structure of Eu³⁺: SrMoO₄ nanometer material,namely the different arrangement of hard MoO₄ tetrahedra along the c-axis and a-axis.Therefore,the structural evolution under pressure is basically governed by the SrO₈ polyhedron.The I4_1/a structure bulk modulus?B₀= 97.70?20?GPa,B?0=4?is considerably higher than the bulk materials.The higher surface energy should be responsible for the improved bulk modulus.3.The high pressure behaviors of the as-synthesized Eu³⁺: SrMoO₄ micron material were investigated by in situ high-pressure synchrotrion angle-dispersive X-ray diffraction,in situ high-pressure Raman scattering,and in situ high-pressure fluorescencemeasurements in diamond anvil cells at room temperature.A phase transition was observed from the scheelite-structured ambient phase?space group I41/a?to a monoclinic fergusonite phase?space group I2/a?at 11.20 GPa,which is considerably lower than the transition pressure of bulk SrMoO₄.The structural modifications are reversible.The diffraction peak corresponding to the crystal plane?2 0 0?moves to the low angle at the phase transition,which indicates that the a axis of the crystal structure has a tendency of elongation with the increasing of pressure.Due to the crystal structure of Eu³⁺:SrMoO₄ micron material,the compression is highly anisotropic,the c-axis being more compressible than the a-axis.Therefore,the structural evolution under pressure is basically governed by the SrO₈ polyhedron.The I4_1/a structure bulk modulus?B₀= 71.90 GPa,B₀=4?is similar to the bulk materials,which is different from the Eu³⁺:SrMoO₄ nanomaterials.