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首页> 外文期刊>Japanese Journal of Applied Physics. Part 1, Regular Papers & Short Notes >Effects of X-Ray Irradiation and Barium Deficiency on Grain Boundary States in BaTiO_3:Ta Ceramics
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Effects of X-Ray Irradiation and Barium Deficiency on Grain Boundary States in BaTiO_3:Ta Ceramics

机译：X射线辐照和钡缺乏对BaTiO_3：Ta陶瓷中晶界的影响

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The effects of x-irradiation and Ba deficiency in BaTiO_3:Ta ceramics were investigated in conjunction with the mechanism of an abrupt increase in electrical resistivity at the Curie temperature T_c, which was called the mode-I positive temperature coefficient of resistivity (PTCR). X-irradiation decreases the resistivity and the potential barrier height at grain boundaries in the rhombohedral and cubic specimens, but increases the ESR intensity of a singlet signal at g = 2.005. On the other hand, introducing Ba deficiency increases the room-temperature resistivity ρ_(RT) and the magnitude of resistivity jump ρ_(mode-I) at T_c, but both ρ_(RT) and ρ_(mode-I) become to decrease when Ba deficiency exceeds 0.03 at%. In highly Ba-deficient specimens, the singlet ESR signal also decreases with increasing Ba deficiency. For explaining the irradiation effects, we proposed two models. One is the hole-recombination model, in which trapped-electrons at V_(Ba)-associated acceptor levels recombine with the holes created by irradiation. The other is the electron-detrapping model for the electrons trapped by acceptor levels. The explanation of the effects of x-irradiation and Ba deficiency was attempted by assuming V_(Ba)-associated centers (V_(Ba), V_(Ba)-V_O, V_(Ba)-F and V_(Ba)-F~+). We conclude that predominant acceptor states at grain boundaries are V_(Ba)-Vo-type defects. It is considered that the mode-I PTCR originals from critical changes in the density of states (DOS) of V_(Ba)-Vo and the Fermi energy at tetragonal-to-cubic transition. This type of trap activation may lead to the formation of V_(Ba)-F~+ and V_(Ba)-F from V_(Ba)-V_O.
机译：结合居里温度T_c下电阻率突然增加的机理，研究了x辐照和Ba不足对BaTiO_3：Ta陶瓷的影响，该机理被称为I型正电阻率温度系数（PTCR）。 X射线辐照降低了菱形和立方样品中晶界处的电阻率和势垒高度，但增加了g = 2.005时单重态信号的ESR强度。另一方面，引入Ba缺乏会增加室温电阻率ρ_（RT）和T_c处的电阻率跃迁ρ_（mode-I）的大小，但是ρ_（RT）和ρ_（mode-I）都会降低钡缺乏超过0.03原子％。在高度缺乏Ba的标本中，单重态ESR信号也随着Ba缺乏的增加而降低。为了解释照射效果，我们提出了两种模型。一种是空穴复合模型，其中与V_（Ba）相关的受主能级的俘获电子与通过辐照产生的空穴复合。另一个是受主能级俘获的电子的电子俘获模型。通过假设V_（Ba）相关中心（V_（Ba），V_（Ba）-V_O，V_（Ba）-F和V_（Ba）-F〜）尝试解释x射线辐射和Ba缺乏的影响+）。我们得出结论，晶界处的主要受体状态是V_（Ba）-Vo型缺陷。可以认为，模式I PTCR是由V_（Ba）-Vo的态密度（DOS）和四方-立方转变时的费米能量的临界变化引起的。这种类型的陷阱激活可能导致由V_（Ba）-V_O形成V_（Ba）-F〜+和V_（Ba）-F。

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