NO126101B

1,195,521. Luminescent materials and uses thereof. COMMISSARIAT A L'ENERGIE ATOMIQUE. 2 Jan., 1969 [18 Jan., 1968; 12 March, 1968; 18 Sept., 1968], No. 189/69. Heading C4S. [Also in Division C1] Thermoluminescent alumina for use as a dosimeter comprises grains having a size less than 400Á, more than 80% being in the form of α-phase crystals; preferably 60% of grains are larger than 10Á. The Al 2 O 3 contains between 100 p.p.m. and 1% by weight Na and traces of 8i0 2 , Fe 2 O 3 , Ti, V and Ge; not more than 20 p.p.m. Mn and Cr should be present. The α-phase is achieved by adding 100 p.p.m. and 1% by weight of F mineralizer during preparation by melting, solidifying and crushing. The Al 2 O 3 is sensitive to X and γ-rays, very high energy neutrons, thermal neutrons and #- radiation. The Al 2 O 3 is used in powder form as mixed with epoxy resin, glass, MgOCI, AlP0 4 , silicones, kaolin, colloidal feldspar or cement binder to form bricks, tiles or slabs containing 70-98% Al 2 O 3 . Bricks are prepared by baking or firing the binder-Al 2 O 3 mixture using a wetting agent and dextrin, molasses or paper pulp to ensure cohesion. The bricks are built into a wall or floor and test samples are removed by drilling if the brick is solid. Alternatively the brick may include cylindrical recesses 6 containing a number of discs 10 for use as test pieces separated by appendages 12 or mounted on columns in place of the appendages. The outer face may be protected by a layer of plastics material or enamel (see Division C1) which may be coloured and contain 50% PbO to act also as a low energy γ-ray filter. The brick is prepared by inserting the disc stacks into the recesses 6 and baking twice. The brick can be reversed and the bases of the recesses used as test samples, alternatively diagonal cuts permit corners of the brick to be removed.