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首页> 外文期刊>Materials Chemistry and Physics >On-line phase transitions of bulk and nanocrystalline La_(1-x)Pb_xMnO_3 (x = 0.3, 0.4, and 0.5) perovskite manganite materials using ultrasonic measurements
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On-line phase transitions of bulk and nanocrystalline La_(1-x)Pb_xMnO_3 (x = 0.3, 0.4, and 0.5) perovskite manganite materials using ultrasonic measurements

机译：使用超声测量，整体和纳米晶La_（1-x）Pb_xMnO_3（x = 0.3、0.4和0.5）钙钛矿锰矿材料的在线相变

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摘要

Bulk and nanostructured La_(1-x)Pb_xMnO_3 perovskite manganite samples for different Pb contents (x = 0.30, 0.40 and 0.50) were synthesised using solid-state reaction and sonochemical methods, respectively. XRD, FTIR, SEM, EDAX, BET and TEM studies were carried out to characterise the prepared bulk and nanosamples. The XRD characterization studies confirmed that the prepared bulk and nano perovskite manganite samples were crystalline in nature. The SEM and TEM studies revealed that the particle sizes of bulk perovskite samples is in the range of 0.75-85 μm, whereas it ranges from 50 to 90 nm in the case of nano perovskite samples. Further, it has been confirmed that there is an increase in particle size with an increase in Pb content both in bulk and nano perovskite samples. In addition, ultrasonic velocities and attenuations of bulk and nanosamples were measured using the on-line ultrasonic through transmission method. The temperature-dependent ultrasonic parameters showed an interesting anomaly in both bulk and nano perovskite samples. The observed marked softening and hardening in sound velocities and attenuation were related to ferromagnetic to paramagnetic phase transition temperature (T_c). In nano perovskites samples, the existence of diffused phase transition took place at a lower temperature compared with the corresponding bulk samples. The observed broad ferromagnetic (FM)-paramagnetic (PM) transition in nano perovskites confirms the absence of sharp transition, which is attributed to the coexistence of orbitally, ordered and disordered phases. The spin-phonon and electron-phonon couplings are known to exist because of single ion magnetostriction and dynamic Jahn-Teller effect, respectively, are evidenced by the observed anomalies in both velocities and attenuations.
机译：分别使用固相反应和声化学方法合成了不同铅含量（x = 0.30、0.40和0.50）的块状和纳米结构的La_（1-x）Pb_xMnO_3钙钛矿锰矿样品。进行了XRD，FTIR，SEM，EDAX，BET和TEM研究，以表征制备的大量样品和纳米样品。 XRD表征研究证实，制备的块状和纳米钙钛矿锰矿样品本质上是晶体。 SEM和TEM研究表明，整体钙钛矿样品的粒径在0.75-85μm的范围内，而对于纳米钙钛矿样品，其粒径在50至90 nm的范围内。此外，已经证实，在块状和纳米钙钛矿样品中，随着Pb含量的增加，粒径增加。此外，使用在线超声透过传输方法测量了超声速度以及大块样品和纳米样品的衰减。与温度相关的超声参数在块状和纳米钙钛矿样品中均显示出有趣的异常。观察到的明显的声速软化和硬化以及衰减与铁磁至顺磁相变温度（T_c）有关。在纳米钙钛矿样品中，与相应的本体样品相比，扩散相变的存在在较低的温度下发生。纳米钙钛矿中观察到的宽铁磁（FM）-顺磁（PM）过渡证实了不存在急剧过渡，这归因于轨道，有序和无序相的共存。已知存在自旋-声子和电子-声子耦合的原因是分别存在单离子磁致伸缩和动态Jahn-Teller效应，这在观测到的速度和衰减异常中得到了证明。

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