The present invention relates to mixed oxide materials, methods for their preparation, detectors for ionizing radiation and CT scanners. In particular, a mixed oxide material is proposed having the formula (YwTbx)3Al5-yGayO12:Cez, wherein 0.01&nlEw&nlE0.99, 0.01&nlEx&nlE0.99, 0&nlEy&nlE3.5 and 0.001&nlEz&nlE0.10 and wherein w+x+3*z=1, whereby the mixed oxide material is doped with at least 10 ppm V.