Preparation And Properties Of Mn⁴⁺ Activated Group V_B Fluoride Fluorescent Materials

White light emitting diodes（W-LEDs）offer the advantages of high energy efficiency and fast response.Current commercial W-LEDs are severely limited in warm,high colour rendering lighting applications due to high colour temperature and poor colour rendering caused by the absence of red light.In order to reduce the colour temperature and improve the colour rendering index,red fluorescent materials need to be added.The Mn⁴⁺activated red fluorescent materials all exhibit good narrow band sharp emission,and the wide blue excitation band of Mn⁴⁺activated fluorescent materials coincides with the excitation region of LED blue chips with low spectral reabsorption,which has become one of the hot spots for research on red fluorescent materials in recent years.K₃NbOF₅（HF₂）:Mn⁴⁺and K₃NbOF₆:Mn⁴⁺red fluorescent materials were prepared by a low temperature solid phase method.K₃NbOF₆:Mn⁴⁺and K₂Ta F₇:Mn⁴⁺red fluorescent materials were prepared by cation exchange method.The main experimental findings are as follows:（1）The K₃NbOF₅（HF₂）:Mn⁴⁺red fluorescent material was prepared by the low temperature solid phase method,and the material was subjected to XRD refinement and electron microscope tracing analysis to determine the physical structure and morphological characteristics of K₃NbOF₅（HF₂）:Mn⁴⁺.The luminescence intensity of K₃NbOF₅（HF₂）:Mn⁴⁺red fluorescent material reached the maximum at Mn⁴⁺doping concentration of 7%.The thermal and water stability properties of K₃NbOF₅（HF₂）:Mn⁴⁺were also tested.At 150℃,the luminescence intensity of the material decreased to 71.2%of the initial intensity,and after6 h of hydrolysis,the luminescence intensity of the material decreased to 63.6%of the initial value.（2）The K₃NbOF₆:Mn⁴⁺red fluorescent material was prepared by a low temperature solid phase method.The fluorescent material was excited at 468 nm and the emission spectrum was narrow band emission with the most significant emission peakν₆ at 630 nm.The luminescence intensity increased with increasing Mn⁴⁺doping concentration,with the maximum luminescence intensity at 7%Mn⁴⁺concentration,then the concentration quenching phenomenon occurs.The increase in temperature and hydrolysis reduced the emission intensity of the fluorescent material to 30%and 56%of the initial value at 150°C and 6 h after hydrolysis,respectively.（3）The K₃NbOF₆:Mn⁴⁺red fluorescent material was prepared by the cation exchange method and a series of emission spectra were measured under 468 nm excitation,leading to the conclusion that the specific cause of the concentration burst was the interaction between the electric dipole-electric dipole.Thermal and water stability tests showed that the luminous intensity of the material at 150°C and after 6 h of hydrolysis decreased to 50.2%and 10%of the initial intensity of the fluorescent material,respectively.The colour purity of the K₃NbOF₆:Mn⁴⁺red fluorescent material was calculated to be 94.4%and the colour temperature to be 4272 K.（4）The K₂Ta F₇:Mn⁴⁺red fluorescent material was prepared by cation exchange and the sample was appearance as a long rod.The luminescence of the The K₂Ta F₇:Mn⁴⁺red fluorescent material was tested and it was found that the ZPL at 619 nm emitted strongly;this was mainly due to the fact that the Mn⁴⁺was in a distorted lattice environment.The material has a colour purity of 89.5%and a colour temperature of 3452 K.