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b0.87
0.07xBa0.10+0.07x)La0.02(Zr0.7Sn0.15Ti0.15)O3 ceramics with 0 # x #1 were prepared by conventional solid-state reaction process, and their dielectric and electric field–induced pyroelectric properties were systemically investigated. Compared with conventional pyroelectric materials, (Pb0.87
0.07xBa0.10+0.07x)La0.02(Zr0.7Sn0.15Ti0.15)O3 ceramics exhibited higher pyroelectric coefficient and figure of merit, which are beneficial for the development of pyroelectric devices. The specimens with x 5 0.65 showed good pyroelectric properties for practical applications. When a 500 V/mm dc bias field was applied, they showed the maximum pyroelectric coefficient of 12,200 lC/m2K and the figure of merit of 106  10
5 Pa
0.5 at 45 °C, which are larger than those observed from conventional pyroelectric materials. Improvement of pyroelectric property is beneficial for the development of infrared detectors.

I. INTRODUCTION

Recently, much attention has been focused on ferroelectric materials with high pyroelectric effect and their applications. Infrared detectors made using ferroelectric materials are widely used in fire alarms, thermal imaging, and intruder detectors because of their high temperature stability, high sensitivity, and low cost.1–3 As we know, temperature dependence of either polarization or relative permittivity of ferroelectrics can be used for the infrared detectors. The former effect is referred to the traditional pyroelectric detector and the latter one is for dielectric bolometer.4–6 Compared with the pyroelectric materials in the first mode, those in the dielectric mode can operate near the transition temperature, and the transition temperature can also shift with the variation in applied electric field.7 In this mode, the pyroelectric coefficient can be written as8 p 5 ðdD=dTÞE 5 ðdPs =dTÞE þ e0 ðder =dTÞE E

;

ð1Þ

where D is the dielectric displacement, T is the temperature, Ps is the spontaneous polarization, E is the applied electric field, e0 is the permittivity of free space, and er is the permittivity of pyroelectric materials. From the pyroelectric equation, it can be known that to achieve a high pyroelectric coefficient, the slope of the dielectric peak must be very steep near Curie temperature under a dc bias field. Lead zirconate stannate titanate (PZST) has been identified as a promising pyroelectric material because Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2011.128 J. Mater. Res., Vol. 26, No. 11, Jun 14, 2011

http://journals.cambridge.org

II. EXPERIMENTAL PROCEDURE

A conventional ceramic process was used to prepare (Pb0.87
0.07xBa0.10+0.07x)La0.02(Zr0.7Sn0.15Ti0.15)O3 (x 5 0, 0.35, 0.65, 0.75, 1) ceramics. PbO, BaCO3, La2O3, TiO2, ZrO2, and SnO2 with the purity of over 99% were used as

a)

1436

its dielectric constant shows a sharp maximum at the Curie point and the dielectric peak is steeper under a dc bias field.9 However, high Curie temperature strongly limits its widespread application. Tuflin et al.10 and Cross and coworkers11 reported that when Ba2+ ion