Ammonium Paratungstate Preparing NaLaMgWO6 Powder

NaLaMgWO₆ powder is the matrix of LED phosphor powder. LED is becoming the future development direction of the illumination source with the series advantages, such as low voltage and power consumption, high reliability, long life, environmentally friendly and energy-efficient. Phosphor plays an important role in the field of LED lighting. Tungstate is typically self-activated luminescent material, the stable emission spectrum, very wide intrinsic luminescence band, occupying most of the visible light region, thus strongly influence the emission band position. Therefore, ammonium paratungstate (APT) as the typical tungstate, is a matrix material with excellent light-emitting property, and can be used for preparing NaLaMgWO₆  phosphor powder which is applied in LED. The steps as following:

1. Weighing NaNO₃, La(NO₃)₃, magnesium acetate and APT at a certain proportion, and dissolving them in deionized water, then adding citric acid to prepare a solution named A; the molar ratio of citric acid : NaNO₃ is (0.05~0.2):1;
2. Adjusting the pH value of solution A to neutral value;
3. The solution A is carried out a hydrothermal treatment, and then removed for centrifugation, washing and drying to obtain a sample powder;
4. Sintering the powder sample to solid phase, to obtain the NaLaMgWO₆ powder. The solid-phase sintering conditions supposed to be: raising the temperature at the rate of 1~2℃/min from room temperature to 200~300℃, and then continually raising to 500-800℃ at 3~5℃/min, holding for 3~8 hours then cooling down.