Tungsten copper electrodes are usually activated sintered by porous tungsten skeleton pre-sintering or mixed powder with active elements. Generally, due to tungsten does not dissolved in the liquid phase copper, which lead to the porosity of high tungsten content of the composite material and has a bad effect on the process of densification. In order to reduce the porosity, we can take advantage of additives which dissolves tungsten.

Adding activate element to promote tungsten dissolution, and of the solid phase sintering and liquid phase diffusion densification during sintering tungsten particles dissolved in the liquid phase precipitation, round and accumulation, to obtain a high density. Its addition can remarkably improve the material properties, reduce the sintering temperature and shortening the sintering time. However, the addition of these elements will be activated in a certain extent, reduce the thermal conductivity and electrical conductivity of tungsten copper electrode. Therefore, this kind of method is suitable for the occasions, which has lower demands of thermal conductivity and electrical conductivity.

Some experiments shows that annealing process has a great influence on the electrical conductivity of tungsten copper electrode, there is a table of the electrical conductivity of W-25Cu tungsten copper electrode at different temperature in the part one.

The table shows that when the annealing temperature reaches 800 ℃, the electrical conductivity of tungsten copper electrode is the highest, after which the temperature continues to rise, the conductivity decreased. Theoretically, this is due to the elimination of internal stress and the Cu phase recrystallization.

On the one hand, when tungsten skeleton is starting cooling process after infiltrated at high temperature, it produce large internal stress because of the a great difference between the coefficient of thermal expansion of tungsten (W) and copper (Cu), which affects the electrical conductivity of tungsten copper electrodes. On the other hand, copper phase recrystallized at 400 ℃, and when the temperature rises to 800 ℃, copper atom lattice distortion reduced, the crystal defects supplemented and improved conduction mechanism of Cu is further reflected. However, with further increase of annealing temperature, changes in Cu phase grain boundaries will gradually slow, the impact on the conductivity becomes negligible.

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After infiltration cooling rate has a great impact on the copper layer quality, too fast cooling will be easy to produce pores and tiny cracks. Meanwhile, due to the furnace temperature unevenness, the copper layer thickness of products are not easy to be uniform, so it requires the use of a copper infiltrated after annealing treatment, which further improving the performance of a tungsten-copper electrode. Some experiments shows that annealing process has a great influence on the electrical conductivity of tungsten copper electrode, there is a table of the electrical conductivity of W-25Cu tungsten copper electrode at different temperature.

Viewed from the electrical conductivity of tungsten copper electrode, it is increasing with the infiltration time. We can learn from the graph that infiltration time from 30 min to 80min, the conductivity of tungsten copper alloy from 32.12% IACS to 38.6% IACS. While the infiltration time continues to increase, the conductivity was reduced from 38.6% IACS to 32.58% IACS.

This is due to the conductive properties of tungsten-copper depends mainly on the copper content and connectivity, as time increases, the amount of copper was infiltrated increases, more evenly distributed organizations tungsten copper, tungsten copper electrode conductivity correspondingly improved. But if infiltration time continued to increase, after that tungsten particles begin to grow up and there may arise organization copper pool, which causes the uneven distribution, so the hardness and conductivity of tungsten copper electrode will decrease.

Connected with the examination of the thermal polycondensation of ammonium paratungstate pentahydrate the chemical and morphological properties of intermediate phases formed during the thermal decomposition of APT have been investigated. We have studied the pH and the turbidity of the aqueous solutions of the intermediate phases, the solubility of the phases, and their rehydratation capability as well as the morphology of the crystallite granules and the grain size distribution. These properties of the original APT have been related to the same properties of the products of decomposition formed between different temperature ranges. The results obtained show unambiguously that each of the above mentioned properties suddenly changes in the temperature range 225 to 250°C. This temperature range coincides with the formation temperature of a new phase called APT II. The most probable formula of APT II is (NH4)8 [H2W13O43(OH)2]·H2O.