Zr,Y,Sb添加のZnOバリスタの課電劣化への影響

摘要

The effects of amount of Sb added to Bi-Mn-Co-Sb-Si-Cr-Ni-Zr-added ZnO varistors on the tolerance characteristics of electrical degradation were investigated. Furthermore, the effects of addition of both Zr and Y to Bi-Mn-Co-Sb-Si-Cr-Ni-added ZnO varistors (the same composition as one of commercial varistors) on the varistor voltage and leakage current were investigated. It was found that addition of Sb enhances the tolerance characteristics to the electrical degradation and the amount of Sb_2O_3 addition of approximately 1 mol% is the optimal. When the amount of added Sb increased, the amount of existence of a Zn_2.33Sb_0.6704-type spinel particle increased, because the amount of existence of Zr compound increased similarly. It was suggested that Zr compound was also related to the electrical degradation characteristic. Varistor voltage decreases a little when the amount of added Zr increases in simultaneous addition of Zr and Y. On the other hand, the value of nonlinear index a hardly changed. Without Zr, the increase in the leakage current accompanying the increase in the amount of added Y, which has been reported conventionally, was not found in this study. However, adding Zr of approximately 0.2 - 0.45 mol%, the leakage current increased by adding Y more than 1 mol% and adding Zr of approximately 0.6 mol%, it decreased.%1．緒言耐課電劣化特性の良好な酸化亜鉛（ZnO）パリスタには様々な添加物が添加されており，添加物やZnとの間の相互作用によって耐課電劣化特性を向上させている（1）～（8）。そこで，従来報告されている耐課電劣化特性が良好なZnOパリスタを作製し，そのパリスタに添加されている添加物の量を変化させると，その添加物と他の添加物の間に働く相互作用が変化し，耐課電劣化特性へ影響を与えることが予想される。これまで避雷器用ZnOパリスタにジルコニウム（Zr）を添加することで，熱衝撃特性の改善，エネルギー耐量の向上（9），ZnOの粒成長の抑制，バリスタ電圧の増大（約250V／m以上），焼成時間の変化による非線形性の改善等が報告されている（10）。