the rectangular sample for performing the second cycle of sintering. Figures 2(a),(b), and (c) correspond to the heating process, constant temperature process at 950C, and cooling process respectively. The three curves in the figures are nearly the same as the corresponding curves of the A-YBCO sample which was sintered in the 6th cycle in ambient air. m It also can be seen that the room temperature resistivity is mucl cn The resistivity decreases to about 0. 129.cm after the heating process is finished. The resistivity of the SG-YBCO shows a shoulder of 2. 77S at 725C from the fig. 2(a). This means that the metal-semiconductor transition occurs in the SG- YBCO sample This temperature is lower than the A-YBCO sample as shown in Table 1. For the A- YBCO sample this temperature appears at about 800C in every rising temperature process. This indicates that the transition temperature ranges from semiconducting-metallic to metallic-semiconducting of the SG-YBCO sample is narrower than that of the A-YBCO sample. This also indicates that the YBCO crystal grain formation of the Sg-YBCO sample is easier than that of the A-YBCO sample 012 2.8 Constant temp:950℃ 0.08 006 2004006008001000 Temperature(℃) Time(min 0.15 ture (C) 10008006004002000 Temperature(℃) Fig. 2. The in-situ HT p-T curves of SG-YBCO sample sintered in the second cycle in the(a) heating process, (b) holding process at 950C and (c)cooling process These figures further indicate that the SG-YBCO sintering process is similar to the A- YBCO sintering process. In the heating process, the sample exhibits semiconducting at the temperatures lower than Tv. It shows a metallic character at heating temperatures higher than Ty. If the temperature rises above Tp, it becomes to semiconducting again. In the constant temperature process(950C) the range of resistivity variation is smaller than the heating or cooling process. In the cooling process, the resistivity of the SG-YBCO sample shows an obvious small peak. For the A-YBCO sample it appears at 690C in the 6 sintering cycle, but for the SG-YBCO sample it appears at 437C as seen in Fig. 2(c). This indicates that the SG-YBCO sample is different from the A-YBCO sample at the O-T phase transition. For our A-YBCO sample the O-T phase5 the rectangular sample for performing the second cycle of sintering. Figures 2 (a), (b), and (c) correspond to the heating process, constant temperature process at 950℃, and cooling process respectively. The three curves in the figures are nearly the same as the corresponding curves of the A-YBCO sample which was sintered in the 6th cycle in ambient air．[11] It also can be seen that the room temperature resistivity is much lower, about 88 Ω·cm. The resistivity decreases to about 0.12Ω·cm after the heating process is finished. The resistivity of the SG-YBCO shows a shoulder of 2. 77Ω at 725℃ from the fig. 2 (a). This means that the metal-semiconductor transition occurs in the SG-YBCO sample again. This temperature is lower than the A-YBCO sample as shown in Table 1. For the A-YBCO sample this temperature appears at about 800℃ in every rising temperature process. This indicates that the transition temperature ranges from semiconducting-metallic to metallic-semiconducting of the SG-YBCO sample is narrower than that of the A-YBCO sample. This also indicates that the YBCO crystal grain formation of the SG-YBCO sample is easier than that of the A-YBCO sample. (a) (b) (c) Fig. 2. The in-situ HT ρ-T curves of SG-YBCO sample sintered in the second cycle in the (a) heating process, (b) holding process at 950℃ and (c) cooling process. These figures further indicate that the SG-YBCO sintering process is similar to the A-YBCO sintering process. In the heating process, the sample exhibits semiconducting at the temperatures lower than Tv. It shows a metallic character at heating temperatures higher than Tv. If the temperature rises above Tp, it becomes to semiconducting again. In the constant temperature process (950℃) the range of resistivity variation is smaller than the heating or cooling process. In the cooling process, the resistivity of the SG-YBCO sample shows an obvious small peak. For the A-YBCO sample it appears at 690℃ in the 6th sintering cycle, but for the SG-YBCO sample it appears at 437℃ as seen in Fig. 2 (c). This indicates that the SG-YBCO sample is different from the A-YBCO sample at the O-T phase transition. For our A-YBCO sample the O-T phase 0 0.03 0.06 0.09 0.12 0.15 1000 800 600 400 200 0 ρ ( Ω·cm) Temperature ( ) ℃ 0.024 0.026 0.028 450 435 420 ρ (Ω·cm) Temperature ( ) ℃ 0.06 0.08 0.1 0.12 0 200 400 600 800 ρ (Ω·cm) Time (min.) Constant temp.: 950℃ -1.4 0 1.4 2.8 4.2 0 200 400 600 800 1000 ln ρ ρ ( Ω·cm) Temperature ( ) ℃