Original Publication Date: 1982-Dec-01
Included in the Prior Art Database: 2005-Feb-10
Chang, IF: AUTHOR [+2]
AbstractThe addition of vanadium oxide significantly improved the cathode ray luminescence efficiency of yttrium gallium garnet and other rare-earth containing garnet phosphors with Tb as an activator.
The addition of vanadium oxide significantly improved the cathode ray luminescence efficiency of yttrium gallium garnet and other rare-earth containing garnet phosphors with Tb as an activator.
It has been well known that an impurity level inclusion of certain transition metals, such as iron, is "toxic" to phosphors since by such inclusion the luminescent properties of the phosphors are often quenched significantly. It appears, on the other hand, that such an impurity sensitive property of phosphors has rarely been explored to improve the phosphor properties. Major effort in the development of rare earth containing phosphors to date has been in the search for host crystals. In contrast, this article describes our finding that the properties of rare earth containing phosphors can be improved significantly by impurity level additives.
Specifically, this invention is based on our discovery that an impurity level addition of vanadium oxide improves the brightness of yttrium gallium garnet phosphors, yttrium aluminum garnet phosphors, and yttrium aluminum gallium garnet phosphors upon cathode ray excitation.
Some of the typical examples are the following. Example I
To obtain a weighed mixture of starting powders consisting of 44 mole% of yttrium oxide, 54 mole% of gallium oxide and 4 mole% of terbium fluoride, 4.75 grams of yttrium oxide, 4.84 grams of gallium oxide, 4.84 grams of gallium oxide and 0.413 grams of terbium fluoride were weighed and mixed. To five separate batches of similar mixtures, 0, 0.01, 0.02, 0.05, and 0.1 mole% of vanadium trioxide were added by weighing 0, 0.00075, 0.00154, 0.00358, and 0.00715 grams of vanadium trioxide and mixed with the other major constituents. The weighed mixtures were further mixed and ground in an agate mortar and pestle until each batch of the powders appeared uniform. These powders were loosely loaded in Pt crucibles covered with Pt sheets and placed in an electric box furnace, which had been controlled at 1450 degrees C. After 20 hours of firing, the X-ray diffraction pattern of the resultant powders showed the structure of yttrium gallium garnet. The powders were then subjected to the luminescence efficiency test by cathode ray excitation. As shown in Fig. 1, the brightness of the phosphrors was found to increase rapidly with increasing vanadium trioxide up to 0.02 mole%, then decrease slightly beyond this point. Example II
To obtain a weighed mixture of powder consisting of 33.5 mole% of yttrium oxide, 62.5 mole% of aluminum oxide, 2 mole% of terbium oxide and 4 mole% of terbium fluoride, 4,87 grams of of yttrium oxide, 4.10 grams of aluminum oxide, 0.471 grams of terbium oxide and 0.557 grams of terbium fluoride were weighed
and mixed. To five batches of similar mixtures of powder, 0, 0.01, 0.02, 0.05, and 0.1 mole% of vanadium trioxide were added by weighing 0, 0.00096, 0.00193, 0.00482 and 0.00964 grams of vanadium trioxide and mixing with the other major co...