Doping and grain size effects on pyroelectric properties of Ba_0.7Sr_0.3TiO₃ for uncooled infrared bolometer

Abstract

Ba 0.7 Sr 0.3 TiO 3 (BST) ceramics with different dopants and various grain sizes were fabricated by the solid-state reaction process, and the doping and grain size effects on dielectric and dc bias field-induced pyroelectric properties were systemically investigated. When acceptors were added, the dielectric loss of the BST was decreased effectively, whereas the pyroelectric coefficient was decreased for the broadening of dielectric constant peaks. With the increase of the content of acceptors and the adding of donors simultaneously, the decrease of pyroelectric coefficient caused by the doping effect could be weakened. The dielectric and dc bias field-induced pyroelectric properties were also affected by the grain size effects dramatically. In this paper, the best pyroelectric coefficient of 105 Â 10 À8 C/cm 2 8C and figure-of-merit of 22 Â 10 À5 Pa À0.5 could be obtained when the grain size was 1 mm. The systemic investigation of doping and grain size effects would contribute to the development of high pyroelectric properties of BST for uncooled infrared detector.

Electrocaloric effect and pyroelectric performance in (K,Na)NbO3‐based lead‐free ceramics

“…A single peak is observed near T C for all samples in the whole studied temperature range, meanwhile the maximum value of p decreases significantly with appropriate BNZ addition just like the dotted blue line in graph. 58,59 The broadening of dielectric peaks is adverse to the p. Besides, the feasibility of the pyroelectric element is also assessed by means of the figures of merit (FOMs), including current responsivity This large p is much higher than the reported results in KNN-based ceramics, 30,52,53 which can be even comparable to that of lead-free or lead-based ceramics.…”

Enhanced pyroelectric properties of porous Ba0.67Sr0.33TiO3 ceramics fabricated with carbon nanotubes

“…They were mixed according to the formula Ba 0.67 Sr 0.33 TiO 3 . 0.6 mol% Mn (NO 3 ) 2 and 1.2 mol% Y(NO 3 ) 3 solutions were added to improve the dielectric and pyroelectric properties [19]. The mixture was then thoroughly ball milled at 350 rpm for 4 h. The dried slurries were calcined at 900°C for 3 h, and then ball milled again at 350 rpm for 4 h. After that, 0.15-0.3 wt% of the homogeneously dispersed multiwall carbon nanotubes slurry was uniformly added into the BST powder by zirconate ball milling at 350 rpm for 4 h with alcohol as milling media.…”

Intrinsic pyroelectric properties of thick, coarse grained Ba 1−x Sr x TiO 3 ceramics

“…In any case, the values obtained for the intrinsic pyroelectric coefficient, without applied electric field, are comparable if not slightly better than previous studies reporting room temperature values (with or without applied electric field) of: about 10 -3 C/m 2 K for BST with 30 % or 33 % Sr content [4,16,22,52], with the mention that 33 % Sr means a lower transition temperature, leading to better pyroelectric properties; total value of (1-4)u10 -3 C/m 2 K for BST with 30 % Sr content, with an applied field of 700 Vmm -1 , including thus the induced part of the pyroelectric coefficient [17]; up to 4u10 -4 C/m 2 K for BST with 30 % Sr, doped with Mn or Y, with an applied field of 400 Vmm -1 [19]; up to 2u10 -4 C/m 2 K for undoped BaTiO 3 thick films and ceramics [67,68]. The values in Table 3 can be further enhanced by doping and by applying an external electric field on the active pyroelectric element in order to increase the contribution of the induced pyroelectric coefficient to the total pyroelectric coefficient defined by equation (1).…”

“…Among pyroelectric materials, barium strontium titanate (Ba 1-x Sr x TiO 3 , BST) is intensively studied for several reasons: Sr is an effective solute for decreasing the paraelectricferroelectric phase transition temperature in a wide temperature range [12][13][14][15], leading to enhanced pyroelectric properties around room temperature; BST compositions are environmentally-friendly materials, which might represent viable alternatives to replace Pbbased oxides; the total pyroelectric coefficient can be very large in materials like BST, as shown in previous literature, especially due to the contribution of the induced part [16][17][18][19][20][21].…”