Renping Cao,Binhui Zhong,Jingheng Nie,Lei Zhang,Yuyu Chen,Lan Li,Ting Chen,Jing Wang
Researchers usually co-dope other ions in Mn 4+ doped phosphors to improve and regulate their luminescence properties for the improvement of their practicality. Here, we synthesize SrLa 2 Al 2 O 7 :R (R Dy 3+ , Mn 4+ , and Dy 3+ /Mn 4+ ) samples by solid-state method in air. The crystal structure and phase purity are confirmed by XRD patterns of samples. We investigate the morphology, luminescence properties, optimal doping concentration of Dy 3+ and Mn 4+ ions, lifetimes as well as the energy transfer from Dy 3+ to Mn 4+ ions. We observe yellow emission of SrLa 2 Al 2 O 7 :Dy 3+ under excitation 355 nm in the region from 450 nm to 650 nm with chromaticity coordinates (0.4684, 0.5035) due to the 4 F 9/2 → 6 H 15/2 and 6 H 13/2 transitions of Dy 3+ ion. SrLa 2 Al 2 O 7 :Mn 4+ under excitation 355 nm emits far-red light in the region from 650 nm to 810 nm with chromaticity coordinates (0.7141, 0.2858) due to the transition 2 E g → 4 A 2g of Mn 4+ ion. SrLa 2 Al 2 O 7 :4mol%Dy 3+ , 0.5mol%Mn 4+ under excitation 355 nm contains the emission of both Dy 3+ and Mn 4+ , and shows red emission with chromaticity coordinates (0.5899, 0.4055). The energy transfer process from Dy 3+ to Mn 4+ ions in SrLa 2 Al 2 O 7 :Dy 3+ , Mn 4+ is verified by the spectral characteristics. The luminous mechanisms of samples are analyzed by energy level diagrams of Dy 3+ and Mn 4+ ions.
Caidan Hou,Zhuo Wang,Jinteng Kang,Ying Xue,Zhuang Liu,Zeyu Ning,Junke Xie,Xin Li
The microwave dielectric properties of SrLa₂Al₂O₇ ceramic, specifically the quality factor ( Qf ) and temperature coefficient of resonant frequency ( τ f ), were enhanced through substituting La 3+ with Sr 2+ at the A-site and Al 3+ with Ti 4+ at the B-site. Pure-phase Sr/Ti co-substituted Sr 1+2 x La 2−2 x Al 2−2 x Ti 2 x O 7 ceramics were synthesized via solid-phase reaction route. Remarkably, at an optimal substitution level of x = 0.55, the resulting Sr 2.1 La 0.9 Al 0.9 Ti 1.1 O 7 ceramic exhibited superior microwave dielectric properties: ε r = 25.94 ± 0.32, Qf = 117,300 ± 5700 GHz ( f 0 = 6.40 GHz), τ f = 3.28 ± 0.17 ppm/°C. The increase of Qf value was highly associated with the low interlayer polarization effect caused by the small absolute value of interlayer polarization charges. The τ f value was jointly dominated by both τ ε and the bond valence of B-site bonds.
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