This paper reports the development of new phosphors using the chemical unit cosubstituting solid solution design strategy. Starting from Lu₃Al₅O₁₂, the Al³⁺–Al³⁺ couple in respective octahedral and tetrahedral coordination was simultaneously substituted by a Mg²⁺–Si⁴⁺ pair forming the Lu₃(Al_2−xMg_x)(Al_3−xSi_x)O₁₂:Ce³⁺ (x = 0.5–2.0) series; as a result, the CeO₈ polyhedrons were compressed and the emission got red-shifted from green to yellow together with the broadening. The evolution of, the unit cell, the local structural geometry as well as the optical properties of Ce³⁺ in these garnet creations, in response to the gradual Mg–Si substitution for Al–Al, were studied by combined techniques of structural refinement and luminescence measurements. The new composition Lu_2.97Ce_0.03Mg_0.5Al₄Si_0.5O₁₂ was comprehensively evaluated regarding its potential application in blue LED-driven solid state white lighting: the maximum emission is at 550 nm under λ_ex = 450 nm; the internal and external quantum efficiencies can reach 85% and 49%, respectively; a 1-phosphor-converted wLED lamp fabricated using the as-prepared phosphor exhibits the luminous efficacy of 105 lm W⁻¹, the correlated color temperature of 6164 K and the color rendering index (R_a) of 75.6. The new solid solution composition series is open for further optimization to enhance the competence for commercial consideration.

Ba ₃ Eu(PO ₄ ) ₃ and Sr ₃ Eu(PO ₄ ) ₃ were synthesized. Their crystal structures were refined and photoluminescence spectra were evaluated. The systhesis conditions for various eulytite-type phosphates with different cation pairs were also summarized.