Tunability and leakage currents of (Ba,Sr)TiO3 ferroelectric ceramics with various additives

Abstract

The Ba x Sr 1−x TiO 3 ferroelectric ceramics with magnesium (BSM) and neodymium (BSN) additives were studied. Measurements were made of tunability, dielectric losses (tan δ), leakage currents, the correlations between current-voltage I (U ) and capacitance-voltage C(U ) characteristics. I (U ) characteristics of high quality BSM ceramics have four regions: Ohmic, where the conductivity is linear; the horizontal region (or negative differential resistivity); the exponential dependence; and the vertical current enhancement. These BSM samples (∼20% Mg additives) were distinguished by highest breakdown strength (more than 1000 V), low tan δ (less than 10 −3 at 1 MHz) and high tunability (up to 10% at E max ∼2 V/μm).

Temperature hysteresis of the capacitance dependence C(T) for ferroelectric ceramics

“…4 The second lack of these materials is their unreliability of the properties after initial influence of electric field that is presented as dielectric hysteresis. The best results to decrease the dielectric loss factor are composed ϳtan ␦ ϳ 10 −3 at nonlinear dependence of dielectric permittivity on bias voltage applied to BST ceramics containing Mg. [10][11][12] However, despite on the reached results 11,12 it is not possible to avoid completely the hysteresis phenomena that play a defining role that used by ceramic BST as the elements revealing electrocaloric effect. The best results to decrease the dielectric loss factor are composed ϳtan ␦ ϳ 10 −3 at nonlinear dependence of dielectric permittivity on bias voltage applied to BST ceramics containing Mg. [10][11][12] However, despite on the reached results 11,12 it is not possible to avoid completely the hysteresis phenomena that play a defining role that used by ceramic BST as the elements revealing electrocaloric effect.…”

Stoichiometry and Grain Boundaries Control by Spark Plasma Sintering in Ba0.6Sr0.4TiO3:Mn/MgO Composites

“…However, all these characteristics are hardly met in standard materials mainly because the reduction of losses requires a smearing out of the ferroelectric behavior, which in turn alters the dielectric tunability . To comply with this intrinsic contradiction and to improve the overall behavior of ferroelectric ceramics, two complementary routes have been used till now: (i) the composite one, based on the mixing between a ferroelectric Ba 1− x Sr x TiO 3 (BST) phase and a low losses dielectric material like MgO; (ii) the chemical one, with the substitution on the ferroelectric active Ti site of BST by cations like Mn . Although a wealth of composites and substitutions have been attempted during the past 15 yrs, the property control toward the optimization of the relative contribution of both routes has not yet been achieved.…”

Fabrication and Dielectric Properties of (Ba0.7Sr0.3)TiO3–Glass Composites

“…Barium strontium titanate, Ba x Sr 1-x TiO 3 (BST), is the most promising material for tunable microwave devices such as phase shifters, varactors, and tunable band filters, [4][5][6][7][8] owing to its high tunability and low dielectric loss at room temperature. Therefore, the fabrication and dielectric tunable properties of BST materials have been extensively studied in three different forms, i.e., bulk ceramics, [9][10][11] thick films, [12][13][14][15] and thin films. [16][17][18][19][20] Each form of BST material has its own specific issue.…”