Disappearance of dielectric anomaly in spite of presence of structural phase transition in reduced BaTiO3: Effect of defect states within the bandgap

Abstract

We report the structural, optical, ferroelectric, and dielectric properties of reduced BaTiO3 samples. For this purpose, oxygen vacancies in BaTiO3 are created by heating these samples with a Ti metal in a vacuum environment at different temperatures. It is observed that with an increase in oxygen deficiencies, the c/a ratio decreases as compared to that of the oxygen treated sample. The ferroelectric properties of the oxygen deficient samples are visibly different as compared to those of the oxygen treated sample. The disappearance of the P-E loop and the anomaly in the temperature variation of the dielectric constant have been observed; however, the structural phase transition corresponding to ferroelectric phase transitions still persists. Thus, it appears that the anomaly in dielectric data and the presence of the P-E loop are getting masked possibly by the Maxwell-Wagner effect. The presence of Ti+3 states in the prepared samples has been confirmed by X-ray absorption near edge structure measurements. The Kubelka-Munk optical absorption shows the presence of extra states below fundamental transition, indicating the emergence of new electronic states within the bandgap, which might be due to Ti+3 states. These new states appear at different energy positions, and with different intensities for different samples, which are reduced in the presence of Ti. These new states within the bandgap appear to modify the electronic structure, thereby reducing the overall bandgap, and hence, they seem to modify the ferroelectric and dielectric properties of the samples. Our results may be treated as experimental evidence for theoretically proposed defect states in oxygen deficient or reduced BaTiO3.

Lattice Defect Engineering Enables Performance-Enhanced MoS2 Photodetection through a Paraelectric BaTiO3 Dielectric

“…60 Accordingly, the Ti 3+ ratio, that is, Ti 3+ /(Ti 4+ + Ti 3+ ), is calculated to be 27.45%, which leads to a defect formula in the present BTO film as 2Ti 4+ + O 2− → O V + 2T i 3+ . 61 The lattice defect states (oxygen vacancies and defective Ti 3+ ) could develop into shallow electronic states in BTO, which would change the insulating state to an n-type conducting state, 62 while the defect states induced sub-bandgap absorption could facilitate enhanced photoabsorption in the MoS 2 /BTO photoheterojunction. This sub-bandgap absorption principle is distinguished from the frequently generated photocurrent via photovoltaic effect of ferroelectric due to the absence of selfpolarization in paraelectrics.…”

Investigation of temperature-dependent optical properties of TiO2 using diffuse reflectance spectroscopy

“…Commercial anatase TiO 2 powder of Alfa Aesar with purity 99.999% has been used for characterization. In order to examine the structural phase purity, X-ray diffraction (XRD) experiment has been carried out on Bruker D8 diffractometer equipped with Cu target having LynxEye detector [6,[19][20][21]. The high-temperature X-ray diffraction measurements were performed to confirm the structural phase transition in the prepared samples.…”

“…The optical band gap of prepared sample has been measured by using DRS measurements [6][7][8]. These measurements have been taken in the 200-800 nm wavelength range using Cary-60 UV-Vis-NIR spectrophotometer having Harrick Video-Barrelino diffuse reflectance probe in the temperature range of 300-450 K [22].…”

“…Diffuse reflectance spectrometer (DRS) is an effective tool to understand the absorption spectra as a function of doping or temperature. The absorption spectra obtained from DRS contain three possible transitions: (1) main absorption spectra which give the information of optical gap [6,7], (2) near absorption edge also called Urbach tail showing amount of disorder present in samples [4], and (3) lower absorption spectra which confirm the presence of defect inside the sample [8,9]. To explore the optical absorption spectra which may be affected from various parameters like temperature, structural transition, doping, etc., an influential work has been done to shape our understanding as to how band gap and disorder varies on semiconducting materials [4,10].…”

Synthesis of Ba1−xSrxTiO3 (x = 0–0.3) Ceramic Powders via Sol‐Gel Method: Structural, Microstructure, Thermal Conductivity, and Compressive Strength Properties

“…[6] Different characteristics and fundamental scientific interest in phase transitions make this material one of the best DOI: 10.1002/crat.202100106 suitable choices for industrial and for the basic scientific comprehending of crystallography, and phase transition. [7,8] Thermal management is an critical aspect in a wide range of applications for the reliability and integrity of devices. Heat capacity, and thermal conductivity are basic thermal transport properties of materials, and understanding these thermal properties of BaTiO 3 is crucial for the performance and design of many devices under hard thermal environment, such as thermal management of electronic packages in the electronic industry.…”