X.Z. Zheng,Z.Y. Ye,Y.F. Zhang,L. Yue,Y.F. Lei,W.B. Dai
With the growing concern about energy consumption, white light-emitting diodes( w LEDs), as the fourth generation of lighting sources, are highly scrutinized by researchers. A series of Bi 3+ /Tb 3+ /Sm 3+ (co)doped BaY 2 Si 3 O 10 phosphors were prepared by traditional solid-state method, and the phase purity was analyzed by X-ray diffraction. In this work, Bi 3+ /Tb 3+ /Sm 3+ theoretically occupies the Ba/Y sites, and this conjecture is also proved by spectral analysis. Under near ultraviolet ( n UV) light excitation, Bi 3+ /Tb 3+ /Sm 3+ is respectively used as the blue ( 3 P 1 → 1 S 0 )/green ( 5 D 4 → 7 F j )/red ( 4 G 5/2 → 6 H j ) luminescence center. Due to the energy transfer (ET) efficiency between Bi 3+ /Sm 3+ is not ideal, Tb 3+ is introduced as a bridge to improve the ET efficiency of the whole system to achieve spectral tunability and application in w LEDs. And at different excitation wavelengths, Bi 3+ emits a wide range of blue to cyan light because it occupies two cation sites. We selected a proper excitation wavelength and obtained an emission spectrum covering the whole visible region. The CIE color coordinates (0.3487, 0.3313), the correlated color temperature (CCT, 4773.61 K), quantum efficiency (QE, 47.62 %), and thermal stability ( T 50 = 537 K) of BaY 2 Si 3 O 10 : Bi 3+ /Tb 3+ /Sm 3+ are discussed in depth, Lu 3+ was used instead of Y 3+ to improve the thermal stability of BYS. Its excellent luminescence performance indicates that this phosphor has potential applications in n UV w LEDs.
A series of novel low-permittivity microwave dielectric ceramics with the compositions of (1- x ) BaY 2 Si 3 O 10 - x Ba 5 Si 8 O 21 (0.3 ≤ x ≤ 0.7) and 0.4 BaY 2 Si 3 O 10 -0.6 Ba 5 Si 8 O 21 - y wt% LiF (1 ≤ y ≤ 3) were successfully synthesized using solid-state reaction sintering. The phase evolution and microwave dielectric properties of these ceramics were systematically studied. X-ray diffraction analysis indicated the coexistence of BaY 2 Si 3 O 10 and Ba 5 Si 8 O 21 phases in the (1- x ) BaY 2 Si 3 O 10 - x Ba 5 Si 8 O 21 system, with no secondary phases detected. In contrast, an additional Ba 2 Si 3 O 8 phase was identified in the LiF-modified composition (0.4 BaY 2 Si 3 O 10 -0.6 Ba 5 Si 8 O 21 - y wt% LiF (1 ≤ y ≤ 3)). Moreover, the Ba 5 Si 8 O 21 phase was found to effectively tune the temperature coefficient of resonant frequency (τ f ) to near-zero values in both systems. Excellent microwave dielectric properties were obtained for the 0.4 BaY 2 Si 3 O 10 -0.6 Ba 5 Si 8 O 21 - 2 wt% LiF ceramic, exhibiting a permittivity ( ε r ) of 7.45, a quality factor ( Q × f ) of 13,152 GHz, and a τ f value of −3.17 ppm/°C. This composition also showed good chemical compatibility with silver electrodes, suggesting its potential for use in low-temperature co-fired ceramic (LTCC) applications.
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