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在空气中450℃时Bi2212相开始发生相分解,在450～550℃温区出现的相分解情况与热处理气氛关系不大;而在更高的温度,其相分解在氧气中比在氮气中剧烈得多。另一方面,经450℃以下温度退火后,Tc和△Tc都基本不变;在450～550℃退火后Tc都升高到85～86K,而几乎与气氛和时间无关;经550℃以上温度退火后,单晶的Tc都有升高,但经氮气退火后的Tc要比经氧气退火后的Tc高;热处理后单晶的超导转变宽度△Tc也反映基本相同的规律,即在450～650℃温区退火后△Tc很窄,仅0.5～1K,而在此范围之外的温度下退火后△Tc与处理前的一样,都较宽。以上结果表明热处理对Bi2212单晶超导电性的影响仅用氧含量的变化是不能给予很好的解释的,而相分解对Bi2212超导电性的变化起着重要的作用。
In the air at 450 ℃ Bi2212 phase began to phase decomposition occurred in the temperature range 450 ~ 550 ℃ phase decomposition and heat treatment atmosphere is not large; and at higher temperatures, the phase decomposition in oxygen than in nitrogen intense Much more. On the other hand, both Tc and △ Tc remained unchanged after annealing at 450 ℃, and Tc increased to 85 ~ 86K after annealing at 450 ~ 550 ℃, which was almost independent of atmosphere and time. After annealing at temperature above 550 ℃ After annealing, the Tc of single crystal is increased, but the Tc after annealing by nitrogen is higher than Tc after oxygen annealing. The superconducting transition width △ Tc of single crystal after heat treatment also reflects the same rule, that is, at 450 △ Tc is very narrow after annealing in ~ 650 ℃ temperature range, only 0.5 ~ 1K, while △ Tc after annealing at a temperature outside this range is as wide as before treatment. The above results show that the influence of heat treatment on the superconductivity of Bi2212 single crystal can not be well explained by the change of oxygen content only, while the phase decomposition plays an important role in the change of superconductivity of Bi2212.