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Whitlockite-type structure phosphors have received extensive attention and research due to their adjustable chemical compositions in isomorphic compounds and providing rich crystal positions for doping activators. Ca 2.6 K 0.2 La 0.2 (PO 4) 2 whitlockite-type phosphors with Dy3+ singly doping and Dy3+, Eu3+ co-doping were prepared via high temperature solid-phase reaction, and the crystallographic characteristics, luminescence properties and temperature sensing performance were investigated in detail. The prepared phosphors are pure phase and both Dy3+ and Eu3+ enter into the matrix and produce blue, yellow and red emissions. The CCT values of the emitted light from Ca 2·6 K 0·2 La 0·2 (PO 4) 2 : Dy3+, Eu3+ phosphors increase with the Eu3+ concentration rises, changing from cold white light to warm white light. The integrated emission intensity of Dy3+ in the phosphor decreases with the change in the doping ratio of Dy3+ and Eu3+, causing by the energy transfer from Dy3+ to Eu3+. The Ca 2·6 K 0·2 La 0·13 (PO 4) 2 :0.06Dy3+, 0.01Eu3+ phosphor shows temperature sensing performance based on FIR technique, with the maximum relative sensitivity calculated to be 0.181% K−1. All the results reveal that the Ca 2·6 K 0·2 La 0·2 (PO 4) 2 : Dy3+, Eu3+ phosphors can be applied to w-LEDs and display devices, and can be used as a new type of optical thermometer. Dy3+/Eu3+ co-doped Ca 2·6 K 0·2 La 0·2 (PO 4) 2 phosphor applied for w-LEDS and temperature sensing. [Display omitted] • Single-phase luminescent materials Dy3+, Eu3+ co-doped Ca 2·6 K 0·2 La 0·2 (PO 4) 2 phosphor with whitlockite structure was synthesized for the first time. • The concentration quenching and energy transfer mechanisms were investigated. • The emission color of Ca 2·6 K 0·2 La 0·2 (PO 4) 2 : Dy3+, Eu3+phosphors changes from natural white light to warm white light with the increase of Eu3+ concentration. • The samples showed temperature sensing performance with maximum S a to be 2.06 × 10−3 K−1 and S r to be 0.181% K−1 under 303 K. [ABSTRACT FROM AUTHOR]

Abstract A series of reddish-emitting apatite-type phosphor LiGd 9 (SiO 4) 6 O 2 :Sm3+ was prepared by using an appropriate solid-state method. The photoluminescence (PL), photoluminescence excitation (PLE) spectra, and decay times of the samples were characterized to investigate the photoluminescence properties for application in white light-emitting diodes (w -LEDs). The photoluminescence investigations showed that LiGd 9 (SiO 4) 6 O 2 :Sm3+ phosphor emitted reddish emission, which ascribed to the transitions of the Sm3+ from the 4G 5/2 excited state to the 6H 5/2 , 6H 7/2 , and 6H 9/2 states, respectively. The critical quenching concentration of Sm3+ in LiGd 9 (SiO 4) 6 O 2 phosphors were determined to be about 3 mol%. Moreover, the spectroscopic data and fluorescence decay dynamics indicate that the energy transfer from Gd3+ to Sm3+ ions takes place in LiGd 9 (SiO 4) 6 O 2 : Sm3+ phosphor. All the results indicated that the LiGd 9 (SiO 4) 6 O 2 : Sm3+ phosphor could efficiently assimilate the near ultraviolet (n -UV) light and act as a suitable warm light candidate for n -UV w -LEDs. [ABSTRACT FROM AUTHOR]

Tb 3+ –Sm 3+ co-doped Ba 3 NaLa(PO 4 ) 3 F phosphors with apatite structure have been prepared by a high temperature solid-state reaction, and their luminescence properties have been investigated in detail. The energy transfer (ET) mechanism was verified as the dipole–quadrupole mechanism, and the ET efficiency as well as the critical distance is also estimated. As a result of fine-tuning of the emission composition of the Tb 3+ and Sm 3+ ions, tunable luminescence properties can be realized by combining the emission of Tb 3+ and Sm 3+ in a single host lattice under UV light excitation. The emission color of the obtained phosphors can be modulated from green to yellow by controlling the doping content of the Sm 3+ ions with the fixed Tb 3+ content. Additional, as the temperature increases from RT to 150 °C, the PL intensities of Ba 3 NaLa 0.7 (PO 4 ) 3 F:0.10Tb 3+ ,0.20Sm 3+ decreased to 80.4% and 78.6% of the initial PL intensity, corresponding to the intensity of transition of Sm 3+ and transition of Tb 3+ in the Ba 3 NaLa 0.7 (PO 4 ) 3 F:0.10Tb 3+ ,0.20Sm 3+ phosphor, respectively. These results indicate the series of Ba 3 NaLa 1− x − y (PO 4 ) 3 F: x Tb 3+ , y Sm 3+ phosphors can be acted as a good candidate for the application in white light-emitting diodes. [ABSTRACT FROM AUTHOR]

Cryolite was considered to be an ideal up-conversion host material due to its low phonon energy, which can effectively suppress the radiation-free transition process of excited state energy levels. In the present paper, a novel up-conversion material K 3 YF 6 :Ho3+, Yb3+ with cryolite structure was prepared successfully using a high-temperature solid state method. The up-conversion luminescence properties of K 3 YF 6 doped with different Ho3+/Yb3+ doping ratio were investigated and the optimal doping ratio were confirmed in this system. Under 980 nm excitation, Ho3+/Yb3+ co-doped K 3 YF 6 revealed a strong green emission at the 541 nm, 549 nm and a weak red emission peaking at 666 nm, corresponding to the 5F 4 , 5S 2 →5I 8 and 5F 5 →5I 8 transitions of Ho3+, respectively. All the red and green up-conversion emission of K 3 YF 6 :Ho3+, Yb3+ belong to two-photon process and energy transfer from Yb3+ to Ho3+ simultaneously. Additionally, to understand the energy transfer and electronic transition process of the red and green light emitted, the possible luminescence mechanism were also analyzed in this paper. All the results indicate that Ho3+/Yb3+ co-doped K 3 YF 6 have potential application value in green up-conversion luminescent materials. • Single-phase up-conversion luminescent materials K 3 YF 6 : Ho3+,Yb3+ with cryolite structure were obtained for the first time. • The up-conversion luminescence properties and mechanism of the as-prepared samples were analyzed under excitation of 980 nm. • Two-phonon up-conversion phenomenon was confirmed. [ABSTRACT FROM AUTHOR]

In this paper, K 3 ScF 6 :Yb3+, Tm3+ phosphor with a cubic cryolite phase were prepared by means of high-temperature solid-state method. The crystal structure and up-conversion luminescence properties of Tm3+ and Yb3+ co-doped K 3 ScF 6 were investigated in detail. Scanning electron microscope (SEM), energy disperse spectroscopy (EDS), elemental mapping and X-ray photoelectron spectroscopy (XPS) were used to analyze the elements composition, elemental distribution and valence states of samples. Under an excitation wavelength at 980 nm, all the samples displayed blue and red emission. When gradually increasing the concentration of Tm3+ in K 3 ScF 6 :0.2 Yb3+, Tm3+ and Yb3+ in K 3 ScF 6 : 0.01 Tm3+, Yb3+, the emission intensity of the samples appeared obviously concentration quenching effect, and the optimum concentration of Tm3+ and Yb3+ were confirmed to 0.01 and 0.20 mol%. Additionally, the effect of pump power on up-conversion emission intensity and the energy transfer mechanism between the Tm3+ and Yb3+ in these samples were analyzed in detail. • Single-phase Tm3+/Yb3+ co-doped K 3 ScF 6 with cryolite structure were synthesized for the first time. • Up-conversion properties of K 3 ScF 6 : Yb3+, Tm3+ were studied. • Mechanism of up-conversion was analyzed. [ABSTRACT FROM AUTHOR]