The following is an example of a combinatorial library to explore the luminescent properties of compositional space variations in the oxide matrix (Y1-xGdx)1-y-zBO3:EuyBiz where y and z run in perpendicular gradients and are =0 to 0.03 in increments of 0.006 for values of x=0.1, 0.2, 0.4 and 0.6 respectively.