The present invention relates to a composite ceramic which comprises a conversion phosphor and a further material, characterized in that the further material has a negative coefficient of thermal expansion, and to a process for the preparation thereof. Furthermore, the present invention also relates to the use of the composite ceramic according to the invention as emission-converting material, preferably in a white light source, and to a light source, a lighting unit and a display device.

The invention relates to an inorganic scintillator material of formula Lu.sub.(2-y)Y.sub.(y-z-x)Ce.sub.xM.sub.zSi.sub.(1-v)M.sub.vO.sub.5, in which: M represents a divalent alkaline earth metal and M represents a trivalent metal, (z+v) being greater than or equal to 0.0001 and less than or equal to 0.2; z being greater than or equal to 0 and less than or equal to 0.2; v being greater than or equal to 0 and less than or equal to 0.2; x being greater than or equal to 0.0001 and less than 0.1; and y ranging from (x+z) to 1. In particular, this material may equip scintillation detectors for applications in industry, for the medical field (scanners) and/or for detection in oil drilling. The presence of Ca in the crystal reduces the afterglow, while stopping power for high-energy radiation remains high.

A scintillation compound can include a rare earth element that is in a divalent (RE.sup.2+) or a tetravalent state (RE.sup.4+). The scintillation compound can include another element to allow for better change balance. The other element may be a principal constituent of the scintillation compound or may be a dopant or a co-dopant. In an embodiment, a metal element in a trivalent state (M.sup.3+) may be replaced by RE.sup.4+ and a metal element in a divalent state (M.sup.2+). In another embodiment, M.sup.3+ may be replaced by RE.sup.2+ and M.sup.4+. In a further embodiment, M.sup.2+ may be replaced by a RE.sup.3+ and a metal element in a monovalent state (M.sup.1+). The metal element used for electronic charge balance may have a single valance state, rather than a plurality of valence states, to help reduce the likelihood that the valance state would change during formation of the scintillation compound.

A scintillation compound can include a rare earth silicate. The rare-earth silicate may be lutetium yttrium orthosilicate. The rare-earth silicate may be doped with Ce. The rare-earth silicate doped with Ce may include a rare-earth element in a tetravalent state at a concentration of at least approximately 10 ppm atomic of the scintillation compound.