| abstract |
Provided is a ceramic substrate for mounting a luminescent element thereon which has a reflectance as high as 90% or above in the ultraviolet to the infrared regions (350-1,000 nm) and which has satisfactory mechanical properties.nThe ceramic substrate (1) for mounting a luminescent element thereon comprises 94-97 mass% aluminum oxide and further contains silicon oxide and at least calcium oxide or magnesium oxide. In a surface (1a) of the substrate (1), when a portion having a surface area of 9.074×10 5 µm 2 is examined with respect to pores having an equivalent-circle diameter of 0.8 µm or larger, the porosity is 2.5-4.5%, the number of the pores is 7,000-11,000, and the cumulative relative frequency of pores having an equivalent-circle diameter of 1.6 µm or smaller in the pore size distribution is 70% or higher. This substrate (1) has a reflectance as high as 90% or above in the ultraviolet to the infrared regions and satisfactory mechanical properties, and is suitable for use in a luminescent device (21). |