Ce3+-substituted aluminum garnet compounds of yttrium (Y3Al5O12) and lutetium (Lu3Al5O12)both important compounds in the generation of (In,Ga)N-based solid state white lightinghave been prepared using a simple microwave heating technique involving the use of a microwave susceptor to provide the initial heat source. Carbon used as the susceptor additionally creates a reducing atmosphere around the sample that helps stabilize the desired luminescent compound. High quality, phase-pure materials are prepared within a fraction of the time and using a fraction of the energy required in a conventional ceramic preparation; the microwave technique allows for a reduction of about 95% in preparation time, making it possible to obtain phase pure, Ce3+-substituted garnet compounds in under 20 min of reaction time. It is estimated that the overall reduction in energy compared with ceramic routes as practised in the lab is close to 99%. Conventionally prepared material is compared with material prepared using microwave heating in terms of structure, morphology, and optical properties, including quantum yield and thermal quenching of luminescence. Finally, the microwave-prepared compounds have been incorporated into light-emitting diode “caps” to test their performance characteristics in a real device, in terms of their photon efficiency and color coordinates.

Structural intricacies of the orange-red nitride phosphor system La(3-x)Ce(x)Si6N11 (0 < x ≤ 3) have been elucidated using a combination of state-of-the art tools, in order to understand the origins of the exceptional optical properties of this important solid-state lighting material. In addition, the optical properties of the end-member (x = 3) compound, Ce3Si6N11, are described for the first time. A combination of synchrotron powder X-ray diffraction and neutron scattering is employed to establish site preferences and the rigid nature of the structure, which is characterized by a high Debye temperature. The high Debye temperature is also corroborated from ab initio electronic structure calculations. Solid-state (29)Si nuclear magnetic resonance, including paramagnetic shifts of (29)Si spectra, are employed in conjunction with low-temperature electron spin resonance studies to probes of the local environments of Ce ions. Detailed wavelength-, time-, and temperature-dependent luminescence properties of the solid solution are presented. Temperature-dependent quantum yield measurements demonstrate the remarkable thermal robustness of luminescence of La2.82Ce0.18Si6N11, which shows little sign of thermal quenching, even at temperatures as high as 500 K. This robustness is attributed to the highly rigid lattice. Luminescence decay measurements indicate very short decay times (close to 40 ns). The fast decay is suggested to prevent strong self-quenching of luminescence, allowing even the end-member compound Ce3Si6N11 to display bright luminescence.

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