Tianhou He

The phase transition sequence and the location of the morphotropic phase boundary region in (1 − x)[Pb (Mg1/3 Nb2/3)O3 ]–xPbTiO3 single crystal

Piezoelectric constant and temperature-dependent dielectric constant measurements have been performed on 110-oriented (1 − x)Pb (Mg1/3 Nb2/3)O3–xPbTiO3 crystals with different compositions under different poling fields. The width of the morphotropic phase boundary region (0.30 < x < 0.35) is determined on the basis of two abnormal regions of the dielectric and piezoelectric properties. An irreversible rhombohedral–monoclinic MA–monoclinic MC–tetragonal phase transition sequence was observed directly from the dielectric constant versus temperature results for 001-poled rhombohedral crystals with compositions near the rhombohedral–monoclinic phase boundary. The structure of the morphotropic phase is shown to be monoclinic with space group Pm.

Orientation dependence of transverse piezoelectric properties of 0.70Pb(Mg1∕3Nb2∕3)O3-0.30PbTiO3 single crystals

In this letter, we present our investigation of transverse piezoelectric performance in 0.70Pb(Mg1∕3Nb2∕3)O3-0.30PbTiO3 (0.70PMN-0.30PT) single crystals with different cuts using a resonance technique. We give the report on the finding of ultrahigh k31 and d31 values of 95.4% and −2517pC∕N, respectively. However, this unusual transverse piezoelectric property is only obtained in crystals with the polarization (thickness) and vibration (length) directions along the ⟨110⟩ and ⟨001⟩ directions, respectively. The 0.70PMN-0.30PT crystal with this cut shows significantly great potential for applications in high-performance transverse-mode piezoelectric devices, such as medical array ultrasonic transducers and actuators.

Optical properties of tetragonal Pb(Mg1/3Nb2/3)0.62Ti0.38O3 single crystal

A systematic study of the optical properties of tetragonal Pb(Mg1/3Nb2/3)0.62Ti0.38O3 single crystals was calculated out at room temperature. It was found that the crystal is transparent in the visible region and rolls off in near 450 nm. The optical absorption edge is around 400 nm under both unpoled and poled conditions. The refractive indices and their dispersion were accurately measured with the minimum deviation method. The parameters Ai, Bi, Ci, and Di of Sellmeier’s equation for both no and ne are also obtained in terms of least-squares fit. Then, the refractive indices in the wavelength range of 435.8–3100 nm can be calculated. Using the Senarmont compensator method, the effective electro-optic coefficient rc=42.8 pm/V was also obtained. Some discussions about the octahedral BO6 structure are presented on the optical properties of the material.

Domain Configuration and Ferroelectric Related Properties of the (110)cub Cuts of Relaxor-Based Pb(Mg1/3Nb2/3)O3–PbTiO3 Single Crystals

Domain configuration and ferroelectric related properties of Pb(Mg1/3Nb2/3)O3–PbTiO3 were investigated as a function of applied electric field for the (110)cub cuts. It was found that a single domain orthorhombic state could be achieved by applying an electric field along the direction cub, but the state after removing the electric field strongly depends on the composition and electric field. A qualitative analysis revealed that a slight variation in composition near morphotropic phase boundaries or in an electric field has a significant influence on domain configuration and piezoelectricity for the (110)cub cuts in Pb(Mg1/3Nb2/3)O3–PbTiO3.

Growth and Dielectric Properties of 0.48 Pb(Fe1/2Nb1/2)O3–0.52 PbTiO3 Single Crystal

Large ferroelectric single crystals of 0.48 Pb(Fe1/2Nb1/2)O3?0.52 PbTiO3 solid solution system were first successfully grown using a modified Bridgman technique and their properties were investigated. The obtained crystals were about 25 mm in diameter, 100 mm in length and black in color. The crystal exhibited abnormal dielectric properties that the dielectric constant was as high as 30000 and the dielectric loss factor was about 0.5 at room temperature. The mechanism of this phenomenon was discussed.

Determination of optical constants of tetragonal Pb(Mg1/3Nb2/3)O3-PbTiO3 ferroelectric single crystals

The optical properties of 0.65Pb(Mg1/3Nb2/3)O3?0.35PbTiO3 (PMN?0.35PT) single crystals were investigated by means of the optical transmittance spectrum. The refractive indices were measured in the visible region, and the dispersion behaviours of ordinary and extraordinary lights were well described in terms of the Wemple?Didomenico single oscillator dispersion model. The optical band gap values were obtained from the Tauc model. For (1 ? x) Pb(Mg1/3Nb2/3)O3 ? xPbTiO3 single crystals, as the PbTiO3 content increases, the refractive index increases, while the optical band gap energy decreases.

Optical properties of tetragonal ferroelectric single crystal lead magnesium niobate lead titanate

The comprehensive optical properties were characterized for tetragonal ferroelectric single crystal 0.65Pb(Mg1∕3Nb2∕3)O3–0.35PbTiO3. The refractive indices were measured using minimum deviation method at different wavelengths, and the dispersion equations were determined for both ordinary and extraordinary rays. Transparent spectrum of the crystal ranges from 450 to more than 2500nm, and the poling process could enhance the transparency dramatically. By the Senarmont compensator method, the effective electro-optic coefficient at 514.5nm wavelength was obtained, γc=93.9pm∕V. These results show that the tetragonal lead magnesium niobate lead titanate single crystals are very promising candidate for a wide range of practical optical devices.

Growth of Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 single crystals directly from melt

Piezoelectric Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 (PZNT 91/9) single crystals were grown directly from melt by a modified Bridgman method. X-ray diffraction confirms that the crystals are of pure perovskite structure. The obtained crystals have piezoelectric constant d33 in the range of 1800–2000 pC/N, which is comparable to that of the PZNT crystals grown from flux. However, compared with the flux-grown PZNT 91/9 crystals, there is a broad diffused peak on the curve of temperature dependence of the dielectric constant, and a lower dielectric peak at 105°C. Domain observation shows that both the rhombohedral and tetragonal orientation states coexist in the morphotrpic PZNT 91/9 crystals.