The influence of direct current bias on the initial aging of a doped lead magnesium niobate ceramic
- PDF / 147,974 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 7 Downloads / 157 Views
MATERIALS RESEARCH
Welcome
Comments
Help
The influence of direct current bias on the initial aging of a doped lead magnesium niobate ceramic Y. Wang Department of Materials Science & Engineering, Tsinghua University, Beijing, People’s Republic of China and Department of Electronic Engineering, City University of Hong Kong, Hong Kong
Y. C. Chan Department of Electronic Engineering, City University of Hong Kong, Hong Kong
Z. L. Gui and L. T. Li Department of Materials Science & Engineering, Tsinghua University, Beijing, People’s Republic of China (Received 27 February 1997; accepted 18 July 1997)
The initial dielectric aging behaviors of a Mg and Mn doped lead magnesium niobate ceramic were investigated over a wide range of direct current (dc) bias. Both the dielectric constant-log(time) and the loss tangent-log(time) were regressed in terms of a linear relationship. The dc bias is found to have a strong influence on the dielectric parameters at the start of aging and to suppress the aging of dielectric constant and loss tangent. The frequency dependence of the dielectric aging is also evidently affected by the dc bias.
I. INTRODUCTION
The dielectric aging behaviors of lead magnesium niobate ceramics have been extensively investigated in the past decade and many important experimental results have been reported.1–4 Nevertheless, there is still much work to be done before the aging mechanism is well understood. From reviewing the papers of aging studies, it is noticed that most of the previous work reported concentrates on weak-field aging and only a few papers mentioned the aging phenomena under direct current bias.4,5 The lack of experimental results on strongfield aging is thought to be due to the difficulty of dielectric measurements on bulk samples under dc bias. For instance, if no specially designed sample fixture is used, the maximum dc bias available in Hewlett Packard LCR meters, one kind of the most widely used instruments in dielectric measurements, is about 40 V. That means if a 1 Vymm electrical field is required in a test, the ceramic sample must be as thin as 40 mm. Such a thin ceramic is easily broken during the sample preparation and tests. On the other hand, if a ceramic sample of normal thickness (such as 0.5 mm) is used, a special fixture must be designed to supply an external voltage (500 V). In this case, the problems are how to protect the instrument from being destroyed by high voltages and how to keep the precision of measurements. These problems are also difficult to solve. The above problem is solved in this work by using a multilayer ceramic capacitor in the investigation. No special fixture is used to supply the high voltage. The internal layer thickness of this MLC is about 25 mm, therefore, the maximum dc bias electrical field available J. Mater. Res., Vol. 13, No. 3, Mar 1998
http://journals.cambridge.org
Downloaded: 25 Mar 2015
for each layer is about 16 kVycm. As will be shown later in this paper, this field is strong enough to affect the aging. With various dc biases app
Data Loading...
