We present our achievement which is a ceramic plate phosphorable to produce white light when directly combined with commercially available blue light emitting diodes. The ceramic phase structure is that the Al₂O₃ particle is uniformly distributed in the Ce:YAG matrix. The Al₂O₃-Ce:YAG ceramic phosphor has a better luminous efficacy than the transparent Ce:YAG ceramic phosphor under the same test condition. The Al₂O₃ particle plays an important role in promoting the luminous efficacy. The Al₂O₃ particle changes the propagation of the light in ceramic, and it reduces the total internal reflection. That is why the composite phase ceramic phosphor improves extraction efficiency of light.

Near infrared (NIR) quantum cutting involving the conversion of an absorbed blue photon into two NIR photons emission has been realized in heavy Yb doped ${\text{Ce}}_{0.03}{\text{Yb}}_{3\text{x}}{\text{Y}}_{\left(2.97-3\text{x}\right)}{\text{Al}}_5{\text{O}}_{12}$ ($\text{x}=0.1$ , 0.25, and 0.5) transparent ceramics. Upon the 467 nm excitation, the energy transfer process was dominated by the cooperative downconversion from the $5d_1$ state of one ${\text{Ce}}^{3+}$ ion to the ${{}^2\text{F}}_{5/2}$ state of two ${\text{Yb}}^{3+}$ ions. The influence of the ${\text{Ce}}^{4+}–{\text{Yb}}^{2+}$ charge transfer state (CTS) should not contribute much to the energy transfer process for the large energy gap between ${\text{Ce}}^{3+}:5d_1$ and the CTS. The calculated quantum yield of ${\text{Yb}}^{3+}$ for the $\text{x}=0.25$ sample without concentration quenching was 175.4%.

The two-phase $\mathrm{Mg}{\mathrm{Al}}_2{\mathrm{O}}_4\text{-}\mathrm{Ce}\text{:}\mathrm{YAG}$ ceramic phosphor was fabricated by the solid-state reaction in vacuum, and it presented a better luminous efficacy than the single-phase transparent ceramic phosphor when directly combined with the blue light-emitting diodes. The addition of $\mathrm{Mg}{\mathrm{Al}}_2{\mathrm{O}}_4$ implemented the control of the grain sizes and the variation of microstructure, and the microstructure optimization further improved the luminous efficacy of the composite phase ceramic phosphor. A maximum luminous efficacy attaining 99 lm/W at the correlated color temperature 5000 K was obtained. The composite phase ceramic phosphor is expected to be a promising candidate for use in the high-power light source.

${\text{Tm}}^{3+}/{\text{Yb}}^{3+}$ codoped ${\text{Y}}_2{\text{O}}_3$ transparent ceramics were fabricated and characterized from the point of upconversion luminescence. All the samples exhibited high transparency not only in near-infrared band but also in visible region. Under 980 nm excitation, the ceramics gave upconversion luminescence with very intense blue (485 nm) and considerably intense violet (360 nm) emissions. It was worthy to point out that the upconversion luminescence contained six emission bands, which dispersed in the region from 294 to 809 nm. The strongest blue emission (485 nm) was obtained with ${\left({\text{Tm}}_{0.002}{\text{Yb}}_{0.03}{\text{Y}}_{0.958}{\text{Zr}}_{0.01}\right)}_2{\text{O}}_3$ ceramic $\left(\text{Yb}/\text{Tm}=15\right)$ . The mechanism of all upconversion emission bands were investigated in detail. The absorption, emission, and gain cross-section of blue emission (485 nm) were calculated, which indicated that ${\text{Tm}}^{3+}/{\text{Yb}}^{3+}$ codoped ${\text{Y}}_2{\text{O}}_3$ transparent ceramic has tremendous potential in short wavelength laser.