Bijun Fang

Dielectric and piezoelectric performance of PMN-PT single crystals with compositions around the MPB: influence of composition, poling field and crystal orientation

Abstract This paper presents a detailed study of the dependence of the dielectric and piezoelectric performance on the composition, poling field and crystallographic direction for Pb(Mg 1/3 Nb 2/3 )O 3 ue5f8PbTiO 3 (PMN–PT) single crystal plates with compositions around the rombohedral–tetragonal morphotropic phase boundary (MPB). The Tmax of the plates lies in the range of 130–160xa0°C. Influence of poling field in a range of 0–3 kV mm −1 on their properties was investigated. Under appropriate poling conditions and with proper compositions, the plates show excellent piezoelectric property with d 33 larger than 1800 pC N −1 along 〈001〉 and 〈011〉, and 1300 pC N −1 along 〈111〉, respectively. It is also suggested that the relaxor nature of PMN, the domain structure modulation and the MPB effect all play important roles in influencing the piezoelectric performance. The possibility of the existence of the induced orthorhombic or monoclinic phase is also discussed in this paper.

Growth mechanism and electrical properties of Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 single crystals by a modified Bridgman method

Abstract Relaxor-based piezoelectric Pb[(Zn 1/3 Nb 2/3 ) 0.91 Ti 0.09 ]O 3 (PZNT 91/9) single crystals 28xa0mm in diameter and 30xa0mm in length were grown by a modified Bridgman technique with PbO flux using an allomeric seed crystal. The crystals were grown in sealed platinum crucibles at about 1250°C. The obtained crystals are of pure perovskite structure within the sensitivity of X-ray diffraction measurement and the as-grown crystals have three appearing faces with slight deviation in angle from the pseudocubic (0xa00xa01) cub face. The growth mechanism of the PZNT crystals could be explained from the viewpoint of the formation of growth units and the incorporation of growth units into different interfaces of the crystal lattice. The growth rate of various crystal faces is related to the assembling modes of the growth units into different interfaces. Assembling of [BO 6 ] octahedral growth unit into (1xa01xa01) cub interface has the strongest bonding force, and this crystal direction has the fastest growth rate; therefore, (1xa01xa01) cub crystal face disappears, assembling of [BO 6 ] into (0xa00xa01) cub interface has the smallest bonding force, and this crystal face has the smallest growth rate; therefore, (0xa00xa01) cub crystal face appears. The growth steps aligning approximately along the 〈0xa00xa01〉 cub direction reveal that (0xa00xa01) cub face proceeds by a layer growth mechanism controlled by two-dimensional nucleation starting at crystal corners or edges. Dielectric measurement proves that the quality of the obtained PZNT crystals is good. Domain observation shows that both the rhombohedral and tetragonal orientation state domain coexist in the morphotropic PZNT 91/9 single crystals.

Crystal orientation dependence of dielectric and piezoelectric properties of tetragonal Pb(Mg1/3Nb2/3)O3-38%PbTiO3 single crystal

Abstract The crystallographic orientation dependence of the P–E behavior and dielectric and piezoelectric properties in tetragonal Pb(Mg 1/3 Nb 2/3 )O 3 –38%PbTiO 3 (PMNT62/38) single crystals were investigated. When the electric field was applied to 15xa0kV/cm the coercive electric fields E c varied from E c [0 0 1] ∼8.25 to E c [1 1 0] ∼6.80 to E c [1 1 1] ∼4.11 xa0kV/cm and the remnant polarizations were P r [0 0 1] ∼34.25 , P r [1 1 0] ∼22.64 , and P r [1 1 1] ∼18.87 xa0μC/cm 2 . In [1xa01xa00] and [1xa01xa01] poled crystals, the formation of the engineered domain configuration caused more enhanced dielectric and piezoelectric activities: d 33[1 1 0] ∼1350 xa0pC/N and e r [1 1 0] ∼6972 ; d 33[1 1 1] ∼980 xa0pC/N and e r [1 1 1] ∼9784 , compared with d 33[0 0 1] ∼350 xa0pC/N and e r [0 0 1] ∼760 at room temperature.

Crystal growth and high piezoelectric performance of 0.95Na0.5Bi0.5TiO3?0.05BaTiO3 lead-free ferroelectric materials

A large single crystal of 0.95Na0.5Bi0.5TiO3?0.05BaTiO3 (0.95NBT?0.05BT) with dimensions of 35?mm diameter ? 10?mm length was grown by the top-seeded-solution growth method (TSSG). X-ray powder diffraction results indicate that the as-grown 0.95NBT?0.05BT crystal is of a perovskite structure and belongs to the rhombohedral system. The dielectric, ferroelectric and piezoelectric properties were investigated in detail. The room temperature dielectric constants for unpoled 0?0?1, 1?1?0 and 1?1?1 oriented crystal samples are 1450, 1650 and 1750 at 1?kHz and decrease to 1050, 800 and 480 after poling. The remanent polarizations Pr of 0?0?1, 1?1?0 and 1?1?1 oriented crystal samples are 16.44??C?cm?2, 23.69??C?cm?2 and 27.63??C?cm?2 with the coercive fields Ec of 32.72?kV?cm?1, 31.20?kV?cm?1 and 28.15?kV?cm?1, respectively. Interestingly, the piezoelectric constant d33 of the 0.95NBT?0.05BT crystal shows apparent anisotropy along its pseudocubic 0?0?1, 1?1?0 and 1?1?1 directions. The 0?0?1 poled 0.95NBT?0.05BT crystals show excellent piezoelectric properties with d33 = 280?pC?N?1. However, the d33 values of the 1?1?1 oriented 0.95NBT?0.05BT crystal are only 90?pC?N?1. The origin of apparent anisotropy in piezoelectric properties has been discussed in detail.

Growth and orientation dependence of electrical properties of 0.92Na0.5Bi0.5TiO3-0.08 K0.5Bi0.5TiO3 lead-free piezoelectric single crystal

A 0.92Na0.5Bi0.5TiO3-0.08 K0.5Bi0.5TiO3 (0.92NBT-0.08KBT) lead-free piezoelectric single crystal with dimensions of Φ 35u2009×u200910 mm was successfully grown by the top-seeded solution growth method. The effective segregation coefficient for K was calculated to be 0.27. An x-ray powder diffraction measurement showed that the as-grown crystal possesses a rhombohedral perovskite structure at room temperature. The room-temperature dielectric constants for poled 〈001〉, 〈110〉, and 〈111〉 oriented crystal samples are found to be 683, 567, and 435 at 1 kHz, respectively. The (Tm, ɛm) values for 〈001〉, 〈110〉, and 〈111〉 oriented crystals are (316u2009°C, 4318), (317u2009°C, 4160), and (318u2009°C, 4348) at 1 kHz, which indicate that the dielectric parameters of the as-grown crystals show weaker anisotropy. The curves, ɛ(T), for the three crystallographic orientations show two anomalies at about 170 and 320u2009°C, respectively, relating to the ferroelectric-antiferroelectric phase and the antiferroelectric-paraelectric phase. There is a...

Enhancing pyroelectric properties of Li-doped (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 lead-free ceramics by optimizing calcination temperature

The 1 wt % Li-doped (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 (BCZT-Li) ceramics were prepared by a citrate method. The effects of calcination temperature on the structure and pyroelectric properties of the BCZT-Li ceramics were investigated. The orthorhombic phase and tetragonal phase coexist in all the BCZT-Li ceramics calcined at different temperatures. All the BCZT-Li powders exhibit the type III adsorption?desorption curves. The increase of calcination temperature leads to the growth of the particle size of the BCZT-Li powders. However, the abnormal growth of grains appears when the calcination temperature exceeds 650 ?C, leading to the deterioration of pyroelectric properties of the BCZT-Li ceramics. The BCZT-Li ceramics calcined at 650 ?C exhibit the best pyroelectric properties, in which the pyroelectric parameters p, Fd, Fv, and Fi is 860 ?C?m?2?K?1, 15.8 ?Pa?1/2 (100 Hz), 0.015 m2/C (100 Hz), and 407.6 pm/V, respectively. The excellent pyroelectric properties of the BCZT-Li ceramics calcined at 650 ?C can be attributed to the polymorphic ferroelectric phase transition occurring around room temperature and the optimized calcination temperature. Such investigations reveal that the BCZT-Li ceramics are promising lead-free materials in the pyroelectric devices.

Phase transition behavior and defect chemistry of [001]-oriented 0.15Pb(In1/2Nb1/2)O3-0.57Pb(Mg1/3Nb2/3)O3-0.28PbTiO3-Mn single crystals

The ferroelectric single crystals 0.5u2009mol.u2009% Mn-doped 0.15Pb(In1/2Nb1/2)O3-0.57Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 (PIMNT-Mn) with rhombohedral perovskite structure were grown by a modified Bridgman method. Dielectric performance analysis reveals that the as-grown PIMNT-Mn single crystals exhibit complex dielectric behavior after polarization, in which the dielectric constant depends on frequency apparently around the ferroelectric phase transition temperatures TR-M and Tm. The temperature and electric-field induced ferroelectric phase transitions were investigated by the temperature dependent unipolar strain curves. The electric-field induced discontinuous ferroelectric phase transitions at elevated temperatures exhibit first-order like phase transition character. The converse piezoelectric constant (d33), maximum strain value (Smax%), and longitudinal electrostrictive coefficient (Q) increase considerably when the temperature approaches the ferroelectric phase transition temperatures TR-M and TM-T. The complex ...

Study of temperature-dependent Raman spectroscopy and electrical properties in [001]-oriented 0.35Pb(In1/2Nb1/2)O3-0.35Pb(Mg1/3Nb2/3)O3-0.30PbTiO3-Mn single crystals

In this work, the temperature-dependent Raman spectra and electrical properties of the [001]-oriented 0.5u2009mol.u2009% Mn-doped 0.35Pb(In1/2Nb1/2)O3-0.35Pb(Mg1/3Nb2/3)O3-0.30PbTiO3-Mn (PIMNT-Mn) single crystals were investigated. All the unpoled and poled PIMNT-Mn single crystals experience a ferroelectric tetragonal phase to paraelectric cubic phase transition (FET-PC) around 183u2009°C (TC), which exhibits a second-order transition behavior. Whereas, the poled PIMNT-Mn single crystals exhibit another two dielectric anomalies around 130u2009°C (TRM) and 148u2009°C (TMT), in which the ferroelectric rhombohedral phase to ferroelectric monoclinic phase (FER-FEM) and the ferroelectric monoclinic phase to ferroelectric tetragonal phase (FEM-FET) transitions take place, respectively. Both the two ferroelectric phase transitions exhibit a first-order transition behavior. The discontinuous change of the phase degree (θ) and frequencies (fr and fa) around TRM suggest the occurrence of the FER-FEM phase transition in the poled PIMN...

Large strain and pyroelectric properties of Pb(Mg1/3Nb2/3)O3–PbTiO3 ceramics prepared by partial oxalate route

Partial oxalate route is an efficient method to synthesize complex perovskite ferroelectric ceramics, in which the synthesized (1 - x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 (PMN–PT) ceramics exhibit rather pure perovskite structure, densified microstructure morphology, and excellent dielectric and piezoelectric properties. The PMN–PT ceramics synthesized by the partial oxalate route exhibit rather symmetric strain–electric (S–E) field hysteresis loops, where the strain is large and far less than saturated at 2 kV/mm. The PMN–PT ceramics exhibit excellent pyroelectric properties, in which the values of the pyroelectric coefficient and the calculated pyroelectric figures of merit maintain almost stable over the frequency range of 100 Hz–2000 Hz, and vary differently depending on composition with the increase of temperature. Such investigations reveal that high-performance piezoelectric and pyroelectric devices can be prepared by the partial oxalate route in low production cost.

Structural phase transition and physical properties of tetragonal 0.85Pb(Zn1/3Nb2/3)O3–0.15PbTiO3 single crystals

Large-size and high-quality 0.85Pb(Zn1/3Nb2/3)O3–0.15PbTiO3 (0.85PZN-0.15PT) single crystals were grown by a modified Bridgman method using an allomeric 0.69Pb(Mg1/3Nb2/3)O3–0.31PbTiO3 single crystal as a seed. The as-grown 0.85PZN-0.15PT single crystals exhibit a tetragonal perovskite structure, which changes wholly into a cubic structure between 190 and 215u2009°C confirmed by high-temperature x-ray diffraction measurement. 0.85PZN-0.15PT exhibits sharp dielectric-response peaks with slight dielectric frequency dispersion where the ferroelectric-paraelectric phase transition is nearly first order. Polarization induces an additional dielectric anomaly around 147u2009°C accompanied by the increase in Curie temperature (TC), the decrease in the value of dielectric maximum (em), and the enhancement of frequency dispersion, which can be assigned to the orientation of a ferroelectric domain or a macro-micro domain transition upon heating. The [001]-oriented 0.85PZN-0.15PT crystal planes exhibit excellent electrical properties, where remanent polarization Pr is 58.27u2002μC/cm2 and piezoelectric constant d33 is around 530–570 pC/N. Pyroelectric coefficient p, detectivity, and voltage responsivity figures of merit Fd and Fv of the 0.85PZN-0.15PT single crystals are 460u2002μC/Ku2009m2, 13.14u2002μPa−1/2, and 0.0302u2002m2/C, respectively, which increase greatly over the temperature range measured. It is needed to improve the temperature stability and the voltage responsivity to meet the requirements of practical applications. 0.85PZN-0.15PT exhibits rather high transparency, with the ultraviolet cut-off edge near 380 nm indicating a low-lying electronic energy gap of ∼3.16u2002eV. The infrared-absorption band occurs at 597u2002cm−1, which can be attributed to the normal vibration of the [Zn1/3Nb2/3]/TiO3 group.Large-size and high-quality 0.85Pb(Zn1/3Nb2/3)O3–0.15PbTiO3 (0.85PZN-0.15PT) single crystals were grown by a modified Bridgman method using an allomeric 0.69Pb(Mg1/3Nb2/3)O3–0.31PbTiO3 single crystal as a seed. The as-grown 0.85PZN-0.15PT single crystals exhibit a tetragonal perovskite structure, which changes wholly into a cubic structure between 190 and 215u2009°C confirmed by high-temperature x-ray diffraction measurement. 0.85PZN-0.15PT exhibits sharp dielectric-response peaks with slight dielectric frequency dispersion where the ferroelectric-paraelectric phase transition is nearly first order. Polarization induces an additional dielectric anomaly around 147u2009°C accompanied by the increase in Curie temperature (TC), the decrease in the value of dielectric maximum (em), and the enhancement of frequency dispersion, which can be assigned to the orientation of a ferroelectric domain or a macro-micro domain transition upon heating. The [001]-oriented 0.85PZN-0.15PT crystal planes exhibit excellent electrical p...