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To maximize the piezoelectric performance of Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) single crystals, a pulse poling (PP) method is proposed in this study. This study investigates the effects of pulse poling on the piezoelectric and dielectric properties of these PMN–PT single crystals and explores the polarization rotation mechanisms. Our findings indicate a significant improvement in the piezoelectric properties postpulse poling. The optimal PP conditions are identified as 30 pulse numbers at a pulsed electric field of 5 kV/cm. The dielectric constant ɛT33/ɛ0 and piezoelectric coefficient d33 of PMN–0.28PT post PP are 7000–7700 and 2200–2530 pC/N, respectively, representing increases of 49% and 66% compared with those of postdirect current poling (DCP). Additionally, the domain structures of the PMN–0.28PT single crystals after various DCP and PP treatments are examined and compared using piezoelectric force microscopy. The enhanced piezoelectric properties are attributed to the finer domain structures, as well as increased domain wall density achieved through PP. This research introduces a novel domain engineering approach to improve the electromechanical properties of relaxor ferroelectric single crystals. [ABSTRACT FROM AUTHOR]

The Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) ferroelectric single crystals have been commercially available as important components in medical ultrasound transducers due to their excellent piezoelectric and electromechanical coupling performance. The variation in piezoelectric and dielectric properties of PMN-PT single crystals with ambient temperature is an important application indicator. In this work, the PMN-PT single crystals after direct current poling (DCP) and alternating current poling (ACP) were subjected to the cyclic thermal treatment process. The thermal cycling stability and microstructural changes in PMN-PT single crystals were investigated. The ACP single crystals exhibit a higher dielectric constant ε 33 T / ε 0 (6500–7600) and piezoelectric coefficient d33 (2100–2500 pC N−1) compared to the DCP single crystals (ε 33 T / ε 0 of 4100–5000, d33 of 1200–1300 pC N−1). Under thermal cycling at 60 °C, the DCP and ACP single crystals exhibit good thermal cycling stability after 150 cycles. Microstructural observations show that the domain structure of the DCP single crystals exhibits "staggered domain walls, inhomogeneous domain size, variety of domain structure," while the relatively homogeneous stripe-like domains were observed in the ACP single crystals. After thermal cycling, new fine striped domains appear in both the DCP and ACP single crystals due to the instability of rotated polarization, but the piezoelectric and dielectric properties are not greatly affected. This work provides an intensive understanding of the effects of thermal cycling on the domain structure, which is useful for applications. [ABSTRACT FROM AUTHOR]

Large-size Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) based ferroelectric single crystals have been grown successfully by the vertical Bridgman method for application in the field of high-end piezoelectric devices. The piezoelectric and dielectric performance uniformity of PMN-PT based ferroelectric crystals is a critical application requirement. Recently, alternating current poling (ACP) has attracted much attention due to its low cost and high efficiency in improving the piezoelectric properties of PMN-PT based crystals. Here, we report the comparison of the performance fluctuation of direct current poling (DCP) and ACP Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) ferroelectric single crystals grown in the [110] direction using the vertical Bridgman method. The fluctuation of piezoelectric coefficient d33, dielectric constant ɛT33/ɛ0, and dielectric loss tanδ was presented. We found that the average d33 and ɛT33/ɛ0 of ACP samples are 1290 and 1500 pC/N and 3890 and 4290 for two different wafers, which were 18% and 23%, 21% and 26% higher than DCP samples. The tanδ of ACP samples was much lower than that of DCP samples. The DCP and ACP samples exhibited the close data of the fluctuation ratios of d33 and ɛT33/ɛ0. The fluctuation ratios of d33 and ɛT33/ɛ0 for DCP and ACP samples are all less than 10%. This work offers a reference for practical ACP technique applications. [ABSTRACT FROM AUTHOR]

Nonlinear optical (NLO) crystals that can generate deep‐ultraviolet (DUV) lasers by the frequency conversion processes play an important role in many basic and frontier research fields. Tetrahedron‐based NLO crystals, which are decent DUV NLO candidates, always exhibit a large DUV transparency window. However, their insufficient birefringence often makes it difficult to satisfy the phase matching condition in the DUV or even UV region. Therefore, some strategies are put forward to improve the phase matching ability of tetrahedron‐based DUV NLO crystals. In this review, the relevant reports are summarized into four categories, including the heterozygosity of tetrahedral groups, the introduction of the planar groups, the combination of the heteroleptic tetrahedrons and the planar groups, and the recombination of polar structures with ferroelectricity. Furthermore, the development tendency of tetrahedron‐based DUV NLO crystals is also discussed. Therefore, this review will be helpful to the exploration of new DUV NLO crystals. [ABSTRACT FROM AUTHOR]

On account of the development of deep-ultraviolet (DUV) nonlinear optical (NLO) crystals, tetrahedron-based compounds have attracted more and more attention, due to their large band gap. Thus, it is urgent to study a lot of these crystals for conducting structural optimization to achieve a balance of optical properties. Thus, this paper designs and obtains the Li2NH4Rb(SO4)2 crystal, an alkali metal sulfate, which is composed of an optimized KBe2BO3F2-like structure and disordered Rb and [NH4] cations. It exhibits a strong second-harmonic generation (SHG) response of 2 × KH2PO4, a large band gap of 7.56 eV and a favorable growth habit to large crystals, simultaneously. Thus, the Li2NH4Rb(SO4)2 crystal is a typical tetrahedron-based DUV NLO example. The coordination of the optimized KBe2BO3F2-like structure and the disordered cations results in the strong SHG response. This structural design strategy will facilitate the exploration of novel DUV NLO crystals. [ABSTRACT FROM AUTHOR]

Alternating current poling (ACP) is an effective method to improve the piezoelectric performance of relaxor-PbTiO3 (PT) ferroelectric single crystal. 0.72Pb(Mg1/3Nb2/3)O3-0.28PbTiO3 (PMN-PT) single crystals have been used to fabricate piezoelectric transducers for medical imaging. Up to date, there are no reports about the full matrix material constants of PMN-0.28PT single crystals poled by ACP. Here, we report the complete sets of elastic, dielectric, and piezoelectric properties of [001]-poled PMN-0.28PT single crystals by direct current poling (DCP) and ACP through the resonance method. The results show that [001]-poled rhombohedral PMN-0.28PT single crystals exhibit the enhancement of longitudinal and transverse piezoelectric properties (${d}_{33} \sim 2000$ pC/N, ${d}_{31} \sim -1010$ pC/N) after ACP. Compared with DCP samples (${d}_{33} \sim 1660$ pC/N, ${d}_{31} \sim -780$ pC/N), the values of ${d}_{33}$ and ${d}_{31}$ increase 20% and 29%, respectively. While the ${d}_{15}$ value decrease from 110 pC/N for DCP sample to 90 pC/N for ACP sample, showing the decrease in transverse shear piezoelectric properties. In addition, the elastic stiffness coefficients ${c}_{11}$ , ${c}_{12}$ , ${c}_{13}$ , the elastic compliance coefficients ${s}_{11}$ , ${s}_{12}$ , and the dielectric constants $\varepsilon _{11}$ , $\varepsilon _{33}$ have great change compared with DCP and ACP samples. This variation of the property matrices provides a reference for high-performance piezoelectric device design. [ABSTRACT FROM AUTHOR]

At present, only KBe2BO3F2 (KBBF) can effectively realize a deep‐ultraviolet (DUV) coherent output, while the layered growth habit seriously hinders its application. Here, a new design strategy with an optimized KBBF‐like structure based on the quasi‐phase matching principle is proposed. Thus, the first KBBF‐like ferroelectric, Li2KRb(SO4)2, is designed. It exhibits a short DUV absorption cutoff edge of 163 nm, a large nonlinear optical (NLO) effect of 1.7 × KH2PO4 under a 1064 nm laser, and typical ferroelectricity. More importantly, it completely eliminates the layered structure by replacing K‐F bonds with strong ‐Li‐O‐S‐ ones as the interlayer force. Therefore, this work finds a new promising DUV NLO candidate, a unity of the DUV transparency, NLO response, and ferroelectricity, which is advantageous to explore new DUV NLO materials. [ABSTRACT FROM AUTHOR]

High-performance piezoelectric materials for actuators, sensors, and transducers are urgently required. It would be ideal to always have high piezoelectric performance and high ferroelectric-ferroelectric phase transition temperature, but we have only one in most cases. Pb(In0.5Nb0.5)O3–PbTiO3 (PIN-PT) crystals have a high rhombohedral-tetragonal phase transition temperature (TRT), but the piezoelectric performance is not very satisfactory. Here, Nd-doped PIN-0.33PT single crystals were grown, where the enhanced piezoelectric d33 and electromechanical coupling coefficient k33 are 2100 pC/N and 91%, which are 80% and 5.8% higher than those for virgin PIN-0.33PT single crystals (1160 pC/N and 86%) and are superior to that of other compositions of PIN-PT crystals. Piezo-response force microscopy was adopted to study the domain structure, and the domain size was found to decrease after Nd doping, which contributes to the enhanced piezoelectric performance. This study offers a good paradigm for enhancing the piezoelectric performance of high Curie temperature ferroelectric single crystals. [ABSTRACT FROM AUTHOR]

Owing to the vital role of birefringent materials in various advanced optical systems, it is very important to find and design structures with a large birefringence. Thus, the LaBO3 crystal was investigated. It exhibits a structural characteristic of quasi-two-dimensional [BO3] layers formed by separate [BO3] groups, which leads to a moderate birefringence (0.093@546 nm). Besides, the LaBO3 crystal presents a short ultraviolet absorption cutoff of 237 nm corresponding to the band gap of 5.23 eV (the calculated value of 4.81 eV). Remarkably, the LaBO3 crystal possesses a large transparency window with a transmittance of more than 60% in the region of 300–2000 nm. Therefore, this study points out a promising birefringent crystal and further confirms a favorable structure of the quasi-two-dimensional [BO3] layer to a large birefringence, which could facilitate the design of new ultraviolet and deep-ultraviolet birefringent crystals. [ABSTRACT FROM AUTHOR]

Nonlinear optical crystals with ferroelectricity, which could realize ultraviolet/deep‐ultraviolet coherent output by the quasiphase matching technology, are expected to be promising candidates for the new type of ultraviolet/deep‐ultraviolet nonlinear optical materials. Here, a new borosilicate crystal, LaBSiO5, is found, which is superior to the famous commercial quasiphase matching crystals, LiNbO3, KTiOPO4, and LaBGeO5 in performances. LaBSiO5 crystal exhibits excellent optical and electrical properties, including a short absorption cutoff (186 nm), a moderate second‐harmonic generation response (≈1.1 × KH2PO4), and the ferroelectric polarization reversal (coercive field ≈ 36.98 kV cm−1, remnant polarization ≈ 1.83 µC cm−2). Besides, no layering tendency is found during the process of crystal growth. Therefore, LaBSiO5 crystal is a potential ultraviolet quasiphase matching material. [ABSTRACT FROM AUTHOR]