YOF:　Yb3+,　Er3+　powders　with　rhombohedral　phase　were　successfully　synthesized　by　using　a　modified　sol-gel　method　with　calcinating　under　a　temperature　range　between　400　°C　and　600　°C.　A　systematic　study　on　the　temperature-dependent　morphology　and　spectroscopic　properties　of　rhombohedral　YOF:　Yb3+,　Er3+　powders　have　been　performed.　The　YOF:　Yb3+,　Er3+　powders　that　prepared　at　400　°C　and　500　°C　exhibit　a　plate　growth　habit,　while　the　powder　that　prepared　at　600　°C　shows　a　sintering　property.　When　excited　by　980　nm　laser　beam,　all　of　the　rhombohedral　YOF:　Yb3+,　Er3+　powders　show　efficient　red　light　emission　with　light　wavelength　ranging　from　630　nm　to　700　nm.　The　upconversion　mechanism　and　luminescence　decay　properties　were　discussed　in　detail.　©2015　The　Royal　Society　of　Chemistry.