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Zaman, Arif,Malik, Rizwan Ahmed,Maqbool, Adnan,Hussain, Ali,Ahmed, Tanveer,Song, Tae Kwon,Kim, Won-Jeong,Kim, Myong-Ho Minerals, Metals & Materials Society and the Insti 2018 Journal of electronic materials Vol.47 No.3
<P>Crystal structure, dielectric, ferroelectric, piezoelectric, and electric field-induced strain properties of lead-free Nb-modified 0.96Bi(0.5)K(0.5)TiO(3)-0.04Bi(Mg0.5Ti0.5)O-3 (BKT-BMT) piezoelectric ceramics were investigated. Crystal structure analysis showed a gradual phase transition from tetragonal to pseudocubic phase with increasing Nb content. The optimal piezoelectric property of small-signal d (33) was enhanced up to similar to 68 pC/N with a lower coercive field (E (c)) of similar to 22 kV/cm and an improved remnant polarization (P (r)) of similar to 13 mu C/cm(2) for x = 0.020. A relaxor-like behavior with a frequency-dependent Curie temperature T (m) was observed, and a high T (m) around 320A degrees C was obtained in the investigated system. This study suggests that the ferroelectric properties of BKT-BMT was significantly improved by means of Nb substitution. The possible shift of depolarization temperature T (d) toward high temperature T (m) may have triggered the spontaneous relaxor to ferroelectric phase transition with long-range ferroelectric order without any traces of a nonergodic relaxor state in contradiction with Bi0.5Na0.5TiO3-based systems. The possible enhancement in ferroelectric and piezoelectric properties near the critical composition x = 0.020 may be attributed to the increased anharmonicity of lattice vibrations which may facilitate the observed phase transition from a low-symmetry tetragonal to a high-symmetry cubic phase with a decrease in the lattice anisotropy of an undoped sample. This highly flexible (at a unit cell level) narrow compositional range triggers the enhancement of d (33) and P (r) values.</P>
Zaman, Arif,Hussain, Ali,Malik, Rizwan Ahmed,Maqbool, Adnan,Nahm, Sahn,Kim, Myong-Ho IOP 2016 Journal of Physics. D, Applied Physics Vol.49 No.17
<P>The dielectric and electromechanical properties of LiNbO<SUB>3</SUB>-modified (1–<I>x</I>) [0.91Na<SUB>0.5</SUB>Bi<SUB>0.5</SUB>TiO<SUB>3</SUB>–0.09Ba<SUB>0.70</SUB>Ca<SUB>0.30</SUB>TiO<SUB>3</SUB>]–<I>x</I>LiNbO<SUB>3</SUB> (abbreviated as (BiNa)TiO<SUB>3</SUB>–(BaCa)TiO<SUB>3</SUB>–LN) lead-free piezoceramics were investigated. The electrical properties revealed that the addition of LiNbO<SUB>3</SUB> (LN) induces a phase transition from a non-ergodic relaxor to an ergodic relaxor in the (BiNa)TiO<SUB>3</SUB>–(BaCa)TiO<SUB>3</SUB>–LN system. A large electrostrain of ~0.418% with a normalized strain of ~690 pm V<SUP>−1</SUP> at 6 kV mm<SUP>−1</SUP> was observed at the coexistence of the non-ergodic relaxor and ergodic relaxor phases for LN 0.020, where a field-assisted reversible phase transition between metastable ferroelectric and stable ergodic relaxor phases occurs. Subsequently, a gradual enhancement in the temperature stability of the dielectric constant was observed. At 3 mol.% LN, a nearly constant temperature and a frequency-invariant permittivity of <I>ε</I> <SUB>r</SUB> ~ 3300 over a broad temperature range of 147 °C–306 °C was observed along with small losses from room temperature up to 400 °C.</P>
Malik, Rizwan Ahmed,Zaman, Arif,Hussain, Ali,Maqbool, Adnan,Song, Tae Kwon,Kim, Won-Jeong,Sung, Yeon Soo,Kim, Myong-Ho Elsevier 2018 Journal of the European Ceramic Society Vol.38 No.4
<P><B>Abstract</B></P> <P>Lead free piezoelectric ceramics (1–<I>x</I>) (0.67Bi<SUB>1.05</SUB>FeO<SUB>3</SUB>–0.33BaTiO<SUB>3</SUB>)–<I>x</I>LiNbO<SUB>3</SUB> with <I>x</I> =0.00, 0.015 and 0.030 were prepared by using conventional mixed oxide route. The incorporation of LiNbO<SUB>3</SUB> into BF–BT system caused no significant change in crystal structure. However, an obvious variation in electrical properties was observed. The <I>x</I> =0.015 composition showed enhanced ferroelectric and electric field-induced strain properties with dynamic piezoelectric constant <I>S</I> <SUB>max</SUB>/<I>E</I> <SUB>max</SUB> =440 pm/V at a relatively low field of 40kV/cm, along with a high working temperature upto <I>T</I> <SUB>m</SUB> =392°C. LiNbO<SUB>3</SUB> addition improved the temperature insensitivity of relative permittivity (ε<SUB>r</SUB>) at high temperatures. At <I>x</I> =0.030, a near-plateau ε<SUB>r</SUB> ∼5000, extended across the temperature range, 200°C–500°C was observed which is advantageous for temperature insensitive dielectric ceramics for high temperature capacitor applications. Large strain and almost temperature invariant ε<SUB>r</SUB> with high working temperature range makes this system suitable for high temperature electronic devices.</P>
Hussain, Ali,Maqbool, Adnan,Malik, Rizwan Ahmed,Zaman, Arif,Lee, Jae Hong,Song, Tae Kwon,Lee, Jae Hyun,Kim, Won Jeong,Kim, Myong Ho Materials Research Society of Korea 2015 한국재료학회지 Vol.25 No.10
$Bi_{0.5}Na_{0.5}TiO_3$ (BNT) based ceramics are considered potential lead-free alternatives for $Pb(Zr,Ti)O_3$(PZT) based ceramics in various applications such as sensors, actuators and transducers. However, BNT-based ceramics have lower electromechanical performance as compared with PZT based ceramics. Therefore, in this work, lead-free bulk $0.99[(Bi_{0.5}Na_{0.5})_{0.935}Ba_{0.065}]_{(1-x)}La_xTiO_3-0.01SrZO_3$ (BNBTLax-SZ, with x = 0, 0.01, 0.02) ceramics were synthesized by a conventional solid state reaction The crystal structure, dielectric response, degree of diffuseness and electric-field-induced strain properties were investigated as a function of different La concentrations. All samples were crystallized into a single phase perovskite structure. The temperature dependent dielectric response of La-modified BNBT-SZ ceramics showed lower dielectric response and improved field-induced strain response. The field induced strain increased from 0.17%_for pure BNBT-SZ to 0.38 % for 1 mol.% La-modified BNBT-SZ ceramics at an applied electric field of 6 kV/mm. These results show that La-modified BNBT-SZ ceramic system is expected to be a new candidate material for lead-free electronic devices.
Malik, Rizwan Ahmed,Hussain, Ali,Maqbool, Adnan,Zaman, Arif,Song, Tae Kwon,Kim, Won Jeong,Kim, Myong Ho Materials Research Society of Korea 2015 한국재료학회지 Vol.25 No.6
New lead-free piezoelectric ceramics $0.96[\{Bi_{0.5}(Na_{0.84}K_{0.16})_{0.5}\}_{1-x}La_x(Ti_{1-y}Nb_y)O_3]-0.04SrTiO_3$ (BNKT-ST-LN, where $x=y=0.00{\leq}(x=y){\leq}0.015)$ were synthesized using the conventional solid-state reaction method. Their crystal structure, microstructure, and electrical properties were investigated as a function of the La and Nb (LN) content. The X-ray diffraction patterns revealed the formation of a single-phase perovskite structure for all the LN-modified BNKT-ST ceramics in this study. The temperature dependence of the dielectric curves showed that the maximum dielectric constant temperature ($T_m$) shifted towards lower temperatures and the curves became more diffuse with an increasing LN content. At the optimum composition (LN 0.005), a maximum value of remnant polarization ($33C/cm^2$) with a relatively low coercive field (22 kV/cm) and high piezoelectric constant (215 pC/N) was observed. These results indicate that the LN co-modified BNKT-ST ceramic system is a promising candidate for lead-free piezoelectric materials.
Dielectric and Ferroelectric Properties of Nb Doped BNT-Based Relaxor Ferroelectrics
Maqbool, Adnan,Hussain, Ali,Malik, Rizwan Ahmed,Zaman, Arif,Song, Tae Kwon,Kim, Won-Jeong,Kim, Myong-Ho Materials Research Society of Korea 2015 한국재료학회지 Vol.25 No.7
The effects of Nb doping on the crystal structure, microstructure, and dielectric ferroelectric and piezoelectric properties of $(Bi_{0.5}Na_{0.5})_{0.935}Ba_{0.065}Ti_{(1-x)}Nb_xO_3-0.01SrZrO_3$ (BNBTNb-SZ, with ${\chi}=0$, 0.01 and 0.02) ceramics have been investigated. X-ray diffraction patterns revealed that all ceramics have a pure perovskite structure with tetragonal symmetry. The grain size of the ceramics slightly decreased and a change in grain morphology from square to spherical shape was observed in the Nb-doped samples. The maximum dielectric constant temperature ($T_m$) increases with increasing amount of Nb; however, ferroelectric-relaxor transition temperature ($T_{F-R}$) and maximum dielectric constant (${\varepsilon}_m$) values decrease gradually. Nb addition disrupted the polarization hysteresis loops of the BNBT-SZ ceramics by leading a reduction in the remnant polarization coercive field and piezoelectric constant.
Ali HUSSIN,Adnan Maqbool,Rizwan Ahmed Malik,김민수,송태권,김명호,Arif Zaman,김원정 한국물리학회 2015 새물리 Vol.65 No.8
Bi0.5Na0.5TiO3 (BNT) templates with a single phase perovskite structure were produced from a plate-like precursor particles of bismuth-layer-structured ferroelectric Bi4.5Na0.5Ti4O15 (BNT4) through a topochemical microcrystal conversion process. First, the plate-like BNT4 precursor particles were prepared via molten salt synthesis. The layered structure BNT4 transformed into a single phase perovskite BNT templates after its topochemical reaction with the complementary Na2CO3 and TiO2 reactants at 950 ℃ for 4 h in a NaCl flux. The as synthesized BNT templates exhibited large grains (range from 10 to 15 μm), had plate-like morphology and exhibits a single-phase perovskite structure with a pseudo-cubic symmetry. Furthermore, the temperature dependences of dielectric constant and loss at different frequencies showed a relaxor behavior, and polarization versus electric field curves exhibited a typical ferroelectric response.