Room temperature synthesis of β-NaGdF4: RE3+ (RE = Eu, Er) nanocrystallites and their luminescence

A roomtemperaturesynthesiswasdevelopedforphasepure β-NaGdF4 nanocrystallitesaswellas5,10, and 20%Eu3þ or 5%Er3þ doped material.RareearthacetatesandNaClreactina1:2Mratiowitha variableexcessofNH4F inethyleneglycolwithin24hours.Sincethethermodynamicstabilityofthe hexagonalphasedecreasesalongthelanthanideseries,alargerexcessofNH4F wasrequiredforthe synthesis ofluminescentsamplesdopedwiththesmallerEr3þ ions thanforEu3þ doped orpure β- NaGdF4. ThematerialswerecharacterizedbypowderX-raydiffraction,electronmicroscopy,andlumi- nescence spectroscopy.TheEu3þ-doped samplesshow 5D0-7FJ and 5D1-7FJ luminescence afterEu3þ excitationat394nmorGd3þ excitationat273nmand308nm.Theratioof 5D1 vs. 5D0 luminescence is influenced bytheexcitationwavelengthandtheEu3þ concentration. TheEr3þ-doped samplesshow green andredupconversionluminescence,respectively,fromthe 2H11/2þ4S3/2-4I15/2 and 4F9/2-4I15/2 transitions after970nmexcitation