The ATO nanoparticles obtained from hydrothermal synthesis

The ATO nanoparticles obtained from hydrothermal synthesis only possess an electrical conductivity of 5·10−4 S/cm. This is contradictory to the results of Zhang and Gao, who claim that this hydrothermal route yields highly conductive ATO nanoparticles without any further thermal treatment, which would indeed set it apart from other methods that are generally reported to require calcination temperatures above 500°C to yield highly conductive materials. However, the BET surface area of 190 m2/g agrees with the data published by Zhang and Gao. The mean primary particle diameter calculated from BET (assuming spherical particles) of 5 nm matches the mean crystalline domain size calculated from XRD patterns, confirming that the primary particles are indeed single crystalline, an essential prerequisite for efficient electron conduction. The maximum size of agglomerates that ultrasonication, measured by SLS, cannot break up is 20 μm. Calcination of the as-synthesized ATO at 600°C enhances its conductivity by four orders of magnitude to 2 S/cm, which easily meets the requirements for electrodes and puts our results in line with the general trend for the conductivity of ATO reported in the literature. The increase in conductivity is attributed to both crystal growth and fusing of primary particles, lowering the number and increasing the contact area of interfaces between particles and thus lowering electrical resistance. As expected, due to crystal growth and sintering, the BET surface area decreases from 190 m2/g to 50 m2/g during calcination. The corresponding particle size of 17 nm agrees reasonably well with the crystallite size of 13 nm calculated from XRD. This surface area still exceeds most reported ATOs with comparable conductivities and is sufficient to enable high capacities. However, calcination also leads to increased agglomerate sizes of up to 200 μm, thus preventing the direct preparation of smooth electrode films of ∼130 μm thickness from calcined ATO. If you are looking for high quality, high purity, and cost-effective ATO, or if you require the latest price of ATO, please feel free to email contact mis-asia.