Investigations on Tl-2223 thin films fabricated through ultrasonic spray pyrolysis under oxygen deficient conditions

[摘要] In this paper we have shown that polycrystalline films corresponding to Tl-2223 phase can be grown by employing high thalliation temperatures and short thalliation times. Ultrasonically deposited precursor films corresponding to Ba₂Ca_2.2Cu_3.3O_ð‘�?(Ag_ð‘�?) have been thalliated under high vacuum (∼ 10^â€�??5 torr) at 890°C to obtain single phase Tl-2223 films. An off-stoichiometric and unreacted pellet of composition Tl_2.05Ba₂Ca₂Cu₃O_ð‘�? has been used as source of Tl. We have shown that oxygen ambient is not necessary for the growth of Tl-2223 phase. The as-thalliated films have ð‘�??_ð‘�?’s in the range 123 K ± 0.70 K. The ð‘�??_ð‘�? has been found to be independent of the addition of AgNO₃ to the precursor. The zero field transport 𝐽_ð‘�? has been observed to be > 1.2 Ã�? 10⁵ A/cm² at 77 K. Near ð‘�??_ð‘�? (110 Kâ€�??122 K), 𝐽_ð‘�? has been observed to follow the power law 𝐽_ð‘�? ∝ (1 â€�?? ð‘�??/ð‘�??_ð‘�?)^ð‘�? , ð‘�? â‰�? 2. A power law with ð‘�? â‰�? 1.4 has been observed for the temperature range 70 Kâ€�??110 K. An optimum doping of Ag has been observed to induce about 25% increase in 𝐽_ð‘�? and it also leads to uniform and enlarged grain growth. The surface morphology of Ag free samples contains plate like grains having arbitrary shapes. In contrast to this 0.35 Ag doped sample exhibits nearly rectangular plate like grains.

[学科分类] 材料工程

[关键词] HTSC;thin films;Tl-2223;ultrasonic spray pyrolysis.