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摘要:近年來，隨著人們對生存環(huán)境的關(guān)注逐漸增加，無鉛壓電材料的研究逐漸成為壓電材料領(lǐng)域的研究熱點。鈦酸鉍鈉基無鉛壓電材料被認(rèn)為是最有希望取代鉛基的壓電材料。采用頂部籽晶助溶劑提拉法（TSSG）生長出具有良好的壓電性能、機電耦合系數(shù)的0.14 at% Mn摻雜的0.95(Na1/2Bi1/2)TiO3-0.05BaTiO3（0.95NBT-0.05BT）單晶。X射線粉末衍射表明，該方法生長的單晶室溫下是三方相結(jié)構(gòu)。隨著溫度的升高，Mn摻雜的0.95NBT-0.05BT單晶發(fā)生系列的結(jié)構(gòu)相變：室溫-230℃呈現(xiàn)三方相結(jié)構(gòu)，530℃轉(zhuǎn)變?yōu)樗姆较啵?80℃時轉(zhuǎn)變?yōu)榱⒎较唷n摻雜的0.95NBT-0.05BT單晶呈現(xiàn)復(fù)雜的電疇組態(tài)，室溫下呈現(xiàn)統(tǒng)計四次對稱性。紅外光譜測試表明，在630cm-1、1300cm-1左右存在紅外吸收峰。拉曼光譜測試表明，在300cm-1，570cm-1，800cm-1出現(xiàn)三個彌散的拉曼峰，分別對應(yīng)[TiO6]的扭曲模，[TiO6]的拉伸模和“軟模”。室溫下，(111)取向的單晶介電常數(shù)、介電損耗最大。極化前(110)切型的單晶的介電性能接近弛豫鐵電體，(001)、(111)切型的單晶的介電性能接近正常鐵電體。極化后單晶的相對介電常數(shù)總體上減小，極化后單晶的介電性能更加接近正常鐵電體。Mn摻雜的0.95NBT-0.05BT單晶呈現(xiàn)典型的電滯回線，隨著頻率的降低和電場強度的增加，電滯回線由窄而狹長的形狀向?qū)挾咏匦蔚男螤钷D(zhuǎn)變，伴隨著剩余極化強度和矯頑場的增大。(001)取向的單晶呈現(xiàn)出最佳的壓電性能，d33值達(dá)到233.4pC/N。隨著溫度升高，Mn摻雜的0.95NBT-0.05BT單晶的壓電常數(shù)、機電耦合系數(shù)基本不變，130℃以上，壓電常數(shù)、機電耦合系數(shù)迅速減小。(110)取向的單晶具有相對較好的熱釋電性能：p值為935.7µC/K·m2，F(xiàn)i值為3859.4pm/V，F(xiàn)v值為0.347m2/C，F(xiàn)d值176.6µPa-1/2。 關(guān)鍵詞：Mn摻雜的0.95NBT-0.05BT單晶；晶型轉(zhuǎn)變；介電性能；壓電性能；鐵電性能；熱釋電性能
Abstract:In recent years, with the increase of environmental concerning, the researches about lead-free piezoelectric materials have become a hotspot in the field of piezoelectric materials. Sodium bismuth titanate based lead-free piezoelectric materials are regarded as the most promising candidates for the lead-based piezoelectric materials so far. 0.14 at% Mn-doped 0.95(Na1/2Bi1/2)TiO3-0.05BaTiO3 (0.95NBT-0.05BT) lead-free single crystals with excellent piezoelectric and electromechanical coupling properties were successfully grown by a top-seeded solution growth method (TSSG). X-ray powder diffraction measurement showed that the as-grown crystal possesses trigonal crystalline structure. With the increase of temperature, successive structural phase transitions occur in the Mn-doped 0.95NBT-0.05BT single crystals. The single crystals exist in trigonal phase between room-temperature and 230℃, which change to tetragonal phase at 530℃, and then change to cubic phase above 580℃. The Mn-doped 0.95NBT-0.05BT single crystals exhibit complex domain configuration with statistical symmetry. The infrared-absorption bands occurr around 630cm-1 and 1300cm-1 observed by the fourier transform infrared spectroscopy (FT-IR) spectra. Three diffused Raman bands center around 300cm-1, 570cm-1 and 800cm-1 observed by the Raman scattering spectroscopy, which can be attributed to the [TiO6] vibration, [TiO6] stretching and “soft mode”. (111)-oriented Mn-doped 0.95NBT-0.05BT crystal planes exhibit the largest values of dielectric constant and dielectric loss. Before poling, the dielectric response character of the (110)-oriented Mn-doped 0.95NBT-0.05BT crystal planes is similar to that of relaxor ferroelectrics, while as the (001)- and (111)-oriented Mn-doped 0.95NBT-0.05BT crystal planes is similar to that of normal ferroelectrics. After poling, the dielectric behavior of all orientations of the single crystals approaches more to normal ferroelectrics accompanied by the decrease of the value of dielectric constant. The Mn-doped 0.95NBT-0.05BT single crystals exhibit typical P-E hysteresis loops, where the shape of the P-E loops changes from narrow to nearly rectangular shape with the decrease of frequency and the increase of electric field, accompanied by the increase of remnant polarization and coercive field. The (001)-oriented Mn-doped 0.95NBT-0.05BT single crystals exhibit the excellent piezoelectric properties, in which the value of d33 is 233.4pC/N. The values of d33 and electromechanical coupling coefficient Kp maintain almost unchangeable, which decrease greatly above the depolarization temperature Td of 130℃. The (110)-oriented crystals exhibit the best pyroelectric properties, in which the values of p, Fi, Fv and Fd are 3859.4 pm/V, 935.7µC/K·m2, 0.347m2/C and 176.6µPa-1/2, respectively. Keywords: Mn-doped 0.95NBT–0.05BT single crystals; structural phase transition; dielectric properties; piezoelectric properties; ferroelectric properties; pyroelectric properties
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