Electronic Supplementary Information Efficient spectral regulation in Ce:Lu3(Al,Cr)5O12 and Ce:Lu3(Al,Cr)5O12/Ce:Y3Al5O12 transparent ceramics with high color rendering index for high-power white LEDs/LDs Tianyuan ZHOUa, Chen HOUa, Le ZHANGa,c,d,e*, Yuelong MAa,b, Jian KANGa,c, Tao LIa, Rui WANGa, Jin HUANGa, Junwei LIa, Zhongying WANGc,e, Farida A SELIMd, Ming LIf, Hao CHENa,c,e* a Jiangsu Key Laboratory of Advanced Laser Materials and Devices, School of Physics and Electronics Engineering, Jiangsu Normal University, Xuzhou, 221116, P.R China b School of Mechanical Engineering, Jiangsu University, Zhenjiang, 212013, PR China c Jiangsu Xiyi Advanced Materials Research Institute of Industrial Technology, Xuzhou, 221400, P.R China d Department of Physics and Astronomy, Bowling Green State University, Bowling Green, 43403, USA e Xuzhou All-to Optoelectronics CO., LTD., Xuzhou 221116, P.R China f Department of Mechanical, Materials and Manufacturing, University of Nottingham, Nottingham NG14BU, UK * To whom correspondence should be addressed Tel: +86-0516-83403242; E-mail: zhangle@jsnu.edu.cn (Le Zhang), chenhao@jsnu.edu.cn (Hao Chen) Supporting figures: Fig S1 Grain size distribution of (a) Ce0Cr01, (b) Ce01Cr0, (c) Ce01Cr01, (d) Ce01Cr02, (e) Ce01Cr03, (f) Ce01Cr04, (g) Ce01Cr05, (h) Ce01Cr06, (i) mean grain size of the prepared TCs The variation trend of grain size as a function of Cr 3+ doping concentration is shown in Fig S1 The mean grain size was calculated by averaging 250 grains observed from the SEM images using the “nano-measure” software It is obvious that the grain size distribution of the sintered TCs was in accordance with normal distribution The average grain size of TCs was moderately increased with increasing the Cr doping concentration However, the grain size of the fabricated TCs was only increased from 2.79 μm to 3.78 μm, owing to the relative low sintering temperature Fig S2 EDS mapping of the sintered Ce01Cr04 sample In order to provide an insight of the elemental distribution of the LuAG TCs, EDS mapping of the Ce01Cr04 sample was carried out, as is shown in Fig S2 It could be clearly seen that all the adopted elements (Lu, Al, O, Ce and Cr) were distributed homogeneously inside the ceramic bulk, indicating that both Ce3+ and Cr3+ ions were solid soluted into LuAG lattice, which was further illustrated the obtained pure LuAG phase of the prepared TCs in Fig Fig S3 Schematic diagram of the energy transfer process between Ce3+ and Cr3+ ions Schematic diagram of the energy transfer process between Ce 3+ and Cr3+ ions is shown in Fig S3 Electrons from the 2F5/2 ground state of Ce3+ ion could be excited to the 2D5/2 excited state by absorbing the 460 nm blue light, and then moved to the 2D3/2 state by cross relaxation Then, the energy transfer process between Ce 3+ and Cr3+ ions could be processed through two means, i.e., radiative transition and non-radiative transition For the radiative transition process, the electrons on the 2D/3/2 state of Ce3+ ion return back to the 2F7/2 ground state to realize 534 nm emission, and a portion of the emission could be absorbed by the 4A2 ground state of Cr3+ ion simultaneously As a result, electrons on the 4A2 state are pumped to the 4T2 excitation state Cr3+ ion, and the emission of Cr3+ ion could be realized, after relaxing the electrons to the 2E state In the case of non-radiative transition process, the relaxed electrons on the 2D3/2 energy level of Ce3+ ion transfer to the 4T2 state of Cr3+ ion directly through non-radiative transition to realize the emission of Cr3+ ions Fig S4 Appearance and transmission spectra of the 0.5 at.% Ce:YAG TC Fig S4 presents the appearance and transmission spectra of the applied 0.5 at.% Ce:YAG TC It could be clearly seen that the Ce:YAG TC exhibited a transparent appearance, and its transmittance at 800 nm was 81.2 %