以室溫共沉法製備Bi2-xVxO3+x粉末應用於固態電解質之研究

Abstract

In the present work,  phased Bi2-xVxO3+x powder has been prepared via chemical precipitation using bismuth chloride (BiCl3) and ammonium metavanadate (NH4VO3) as starting materials while NaOH was applied as the precipitating agent. The precipitation was performed under room temperature. In the first part of this study, the influence of the NaOH/Bi (N) ratio, on the phase composition of the precipitate was investigated. XRD and SEM results revealed that  phase Bi2-xVxO3+x crystals in cubic morphology could be only obtained at a N ratio above 80.; otherwise, BiOCl3 was coexisted. The second part is to observe their reaction mechanism by changing the reaction time. According to the time-resolved experiment, XRD peaks of the precipitate showed a shift to the higher degree due to the incorporation of V5+ ions into the g-Bi2O3 structure with increasing the reaction time. The peak shift became unchanged after reacting for 12 hours, implying that the introduction of V5+ ions was limited. In the third part of this study, the doping ratio of V5+ (Bi2-xVxO3+x, x = 0.01 – 0.5) was varied. The XRD and SEM characterizations showed that some rod-like crystals corresponding to the α phased Bi2O3 was coexisted when the V5+ doping ratio was less than x = 0.03. With increasing V5+ doping ratio, the amount of g-Bi2O3 in cubic morphology gradually increased and became the unique phase when the V5+ doping ratio was more than x = 0.1. According to the DTA/TG investigation, an endothermic peak was observed at 830 °C which is related to the transformation of g-Bi2O3 to d-Bi2O3. Accordingly, the compacts of the synthesized Bi2-xVxO3+x, (x = 0.1 – 0.5) powders were sintered at 800oC for 24 h to increase the bulk density higher than 90%. It was shown that the sintering treatment did not change the phase composition for Bi2-xVxO3+x, (x = 0.1 – 0.4); however a second phase related to a new cubic-structure Bi2O3 (JCPDS 74-1373) was appeared for Bi2-xVxO3+x (x = 0.5). It implied that this second phase could be only formed under high temperature. The ion electric conductivity of Bi2-xVxO3+x (x = 0.1 – 0.5) sintering bodies was measured by DC method. It was observed that the conductivity increased with increasing the amount of V5+ up to x = 0.4. When Bi3+ was replaced by V5+, interstitial oxygen ions were produced in order to reach the structural charge balance that promoted the conductivity. The conductivity was attained 0.0075 S/cm at 800 °C for Bi2-xVxO3+x (x = 0.4) and abruptly decreased for Bi2-xVxO3+x (x = 0.5) mainly due to the formation of second phase.