INTRODUCTION In recent years, perovskite structure compounds, especially ABO 3 (A = Sr, Ba, Pb, Ca and B = Ti, Zr) have been paid attention and researched popularly because of their great applications in technology and practicality. ABO 3 materials have interesting characters, such as optical, ferroelectric and piezoelectric responses and others. Therefore, these materials have been applied to make capacitor, rheostat, photoelectrodes, ferroelectric storage, gas sensor. In group of ABO 3 materials, one of the most researched materials is dielectric Strontium titanate, SrTiO 3 (STO), especially after their ferroelectric responses were investigated. Because of high dielectric constant, which increases as freezing and has low short-wave loss, this material is applied in devices with high frequency, short-wave, even at low temperature. There are many researches on STO focusing on Ti or Sr doping or replacing with metal ions to investigate the distortion of perfect cubic structure that causes interesting physical phenomena. In the report about doping Sr in SrTiO 3 , it was shown that replacing metallic ions for Sr position caused the suppression of paraelectric state. Substitution of Bi for Sr leads to the occurrence of several polarization modes and phase transition to ferroelectric behavior. La doping in STO materials strongly suppresses the paraelectric state, without the occurrence of intrinsic polarization modes, except for polarization effects related to oxygen vacancies. SrTiO 3 doped with transition metal M have been researched excitingly by many authors. Recently, in application as sensor, Fe doped STO with high concentration has been synthesized successfully and applied as transport emission level. This material carries required stability and transport properties at relatively high temperatures. Most investigation of Fe doped STO focus on effects of Fe on structure, size of grains, impedance spectroscopy and Raman spectra at room temperature. As we know, STO is material with high dielectric constant (at room temperature, ε = 300). Ti ion exists at 3d 0 state, so this material does not have magnetic characters. Lately, ferroelectric properties of doped STO with magnetic ions have been discovered and it is hoped that this response can be applied in spintronics. When investigating Co substituted TiO 2 , Matsumoto et al found ferromagnetic properties of the material at the room temperature, which introduced new research approaches on oxide materials with Ti. Then, many researches have been carried out with good results. However, the origin of ferroelectric in these materials has not been explained thoroughly and there are many opposite opinions. For example, with Co substituted STO, ferromagnetic properties occur in bulk materials with high Co content, but does not occur in thin film materials. In many reports about groups of dielectric materials doped with transitional metals M, structure, electric and magnetic properties, Raman spectrum at room temperature have been focused on research, while optical responses and Raman at low temperature have been hardly researched. There have several studies on Raman scattering spectroscopy it low temperature but do not systematic, specially on the effect of transitional metals Fe, Co, Ni on electromagnetic responses and optical responses of SrTi 1-x M x O 3. STO materials doped with transition metal (Fe, Co, Ni) are not only interesting and complicated research object on material science, but also promising ones in application in Spin electronics, Diluted Magnetic Semiconductor (DMS). Basing on practical situation and research condition such as experimental devices, references, research ability and research groups in Vietnam and abroad the following study and solutions to unsolved problems are feasible and may give good results. Therefore, we chose the topic of thesis: "Preparation of SrTi 1-x M x O 3 (M = Fe, Co, Ni) system and investigation some their properties" The purpose of thesis is: (i) Preparation of SrTi 1-x M x O 3 (M = Fe, Co, Ni) systems by sol-gel and Pulsed Laser Deposition (PLD) method. (ii) Investigating effects of substituted content on their structural, ferroelectric and optical properties. Research methods: Experimental method with data analysis was used to investigate the effects of the substitution on the structure as well as properties of materials. We used polycrystalline samples made by sol-gel and PLD methods in the laboratory of Center for Nano Science and Technology, Hanoi National University of Education. Structure morphology and components of samples were examined by X-ray diffraction, Scanning Electron Microscopic (SEM), Atomic Force Microscope (AFM) and Energy Dispersive Spectra (EDS). Impedance measurement was performed by Le-Croy using Lab-View 8.0 in the Center for Nano Science and Technology, Hanoi National University of Education. Raman scattering spectroscopy measurement at low temperature which used in Ewha University, Korea was carried out on spectrometer device T6400, using activate laser of 514 nm in 10-300 K. Besides that, measurement of magnetic, Raman scattering spectroscopy at room temperature, absorption spectra were also performed by devices having high accuracy at various laboratories in Vietnam. Exciting source of both Raman was Ar laser of 514 nm. Magnetic measurement was used by DMS 880 (Digital Measurement System Inc), basing on rules of vibrating sample magnetometer with sensitivity of 10 -5 emu at Material Science Center of University of Science Vietnam National University. Absorption spectra of samples were measured on Jasco 670 UV at laboratory of Physics Department of Hanoi National University of Education. Diagram of energy and density of state were calculated by Material Studio. The thesis includes: overview about perovskite Strontium titanate (SrTiO 3 ), experimental methods, results of researches on effects of Fe, Co, Ni substitution on structure, electromagnetic and optical properties of SrTi 1-x M x O 3 samples synthesized by Sol-gel and PLD method Composition of the thesis: the thesis consists of 140 pages, including introduction, 5 chapters of content, conclusion and references. The detailed composition as follow: Introduction Chapter 1: Overview on SrTiO 3 materials Chapter 2: Experimental methods Chapter 3: The effects of Fe, Co, Ni substitution on structure of SrTi 1-x- M x O 3 materials Chapter 4: The effects of Fe, Co, Ni substitution on electromagnetic properties of SrTi 1-x M x O 3 materials Chapter 5: The effects of Fe, Co, Ni substitution on optical properties of SrTi 1-x M x O 3 materials Conclusion References The main results of the thesis were reported 5 articles on international journals and 5 ones specific conferences. Chapter 1 OVERVIEW ON SrTiO 3 MATERIALS 1.1. Crystal structure of SrTiO 3 materials Strontium titanate SrTiO 3 (STO) is one of the important compounds in the group of perovskite ABO 3 . At the room temperature, STO materials have cubic structure, with crystal space of P m3m ( 1 h O ) and lattice constant of 3.905 Å. Corner positions of cubic are Sr cations, center of 6 sites is oxygen anion, center of the cubic is Ti cation. Ion Sr 2+ has coordination number of 12, radius of r Sr +2 = 1.44 Å. Ion Ti 4+ has coordination number of 6, radius of r Ti +4 = 0.605 Å. Ion O 2- has coordination number of 8, radius of r O −2 = 1.42 Å. Figure 1.1 is perovskite at room temperature. At the low temperature, the materials show phase transition from cubic structure into tetragonal one of I 4/mcm (105 K). In the stoichiometric composition, ratio Sr/Ti = 1, O/Sr = 3, STO is dielectric with band gap energy of 3.2 eV. State 2p of oxygen predominates at peaks of valence band and 3d state of Ti predominates on conduction band. STO show both covalent bond and ionic bond. Hybridization between 2p state of oxygen and 3d state of Ti presents covalent bond and between ion Sr 2+ and O 2- presents ionic bond. The important character of STO structure is existence of octahedral TiO 6 in basic cells. In the perfect state, octahedral TiO 6 has 90 o angle and the length of 6 bonds is 1.952 Å. The distance of ion O 2- and ion Sr 2+ in each site of the cubic is 2.769 Å. However, in the distortion state, depending on the chemical component of materials, crystal structure is not the cubic, the bond distance is not homogeneous and physical properties of the materials are also effected. 1.2. Properties of SrTiO 3 materials 1.2.1. Electromagnetic properties of SrTiO 3 materials Dielectric properties of STO used to be investigated by impedance spectroscopy measurement. Impedance spectroscopy is more general than impedance because it includes phase shift between electric voltage and current. Normally, vector quantity is presented by relation ' " Z( ) Z jZ ω = + , in which Z’ is the real part and Z’’ is the imaginary part. On the complex plane, impedance diagram is presented as figure 1.2 with: ' Z Z cos( ) θ = , " Z Z sin( ) θ = , '' 1 ' Z tan Z θ −   =     , 1 '2 ''2 2 Z (Z Z ) = + θ is the angle between impedance Z and the real part Z’. Theoretically, dependence expression of the real and imaginary part is semi-circle having center on the material axis. Practically, due to different Sr Ti O Figure 1.1. Perfect cubic perovskite SrTiO 3 and arrangement of octahedral TiO 6 . . Figure 1.2. components in complex impedance Z θ Z ’’ Z ’ Z 0 Y X restoration time, the semicircle can be distortion having center under the material axis X. Guo et al investigated impedance spectroscopy of single crystal and crystal of STO. The result for single is 2 semicircles with the contribution of grain and grain boundary (figure 1.4a), for crystal is 3 semicircles, in which the one at high frequency is contributed by grain local, the one at the low frequency is contributed by electrodes, at the medium by grain boundary. From the cross point of these semicircles with material axis, we can define resistance of grain, grain boundary and electrodes. It is known that in the perovskite ABO 3 material at B sites are ions of transition metal. Cations B with d orbit are the condition that magnetic moment and magnetic order exist. For dielectric materials SrTiO 3 , ion Ti 4+ haven’t electronic orbit d (d o ), so there is not magnetic properties in the pure STO. The magnetic properties occur only when replacing or doping metal ions for ion Sr 2+ , Ti 4+ ion O 2- . 1.2.2. Optical properties of SrTiO 3 materials For the optical properties of SrTiO 3 materials, it was often focused on Raman scattering spectroscopy. Theoretically, correlation method can be used to calculate Raman and infrared active modes in STO crystal. The results show that in this material, mode 3F 1u is active infrared and F 2u is inactive Raman and infrared. Optical phonons were also investigated in many reports. Oscillation modes which are typical of 1 st Raman scattering are: TO 1 mode at around 90 cm -1 , TO 2 -LO 1 band at around 170 cm -1 , TO 3 -LO 2 mode is inactively optical one (266 cm -1 ), mode TO 4 at 545 cm -1 , LO 4 -A 2g at 795 cm -1 . Oscillation modes for 2 nd Raman scattering are between 200-400 and 600-800 cm -1 . The Raman -Z’’ (Ω) Z’ (Ω) Figure 1.4. Impedance spectroscopy (a) of STO single crystal and (b) of STO crystal at 773 K in Ar. scattering spectroscopy at low temperature indicate that in STO, there appears phase transition from cubic to tetragonal structure at 105-110 K. For perovskite ABO 3 materials having B site with ions of transition metal of d group, elements of d and oxygen define properties of materials. Basing on estimation of energy band, it can be seen that orbital s, p of A have no influence on width of covalent band ABO 3 . From diagram of reduced energy of STO (figure 1.10) K. V. Benthem et. al said that absorbing edge is in accordance with shift from 2p of oxygen and 4p of Strontium to 3d of Titanium. At near Fermi level, there is hybridization of p and d. 3d state affects the conduction band and 2p of oxygen in the valence band. The width of band gap energy is around 3.2 eV, which means that 2p of oxygen at peaks of valence band to 3d of Ti t 2g and e g in conduction zone. Bonding of Sr and TiO 6 is strong ionic bonding, while covalent bonding of Ti and O is the result of 2p (O) and 3d (Ti). 1.3 The effects of substitution on the structure and properties of SrTiO 3 1.3.1. The substitution at site A 1.3.2. The substitution at site B 1.4. Chemical defects of SrTiO 3 in replacing donor and acceptor 1.4.1. Chemical defects 1.4.2. Defect chemistry of donor doped SrTiO 3 . 1.4.3. Defect chemistry of undoped and acceptor doped SrTiO 3 Figure 1.10. Schematic energy level for STO Figure 1.11. Density of state of STO 1.5. Effect of processing parameters on the microstructural and electrical properties of the STO crystal 1.5.1. Stoichiometric and nonstoichiometric composition of STO 1.5.2. Sintering temperature 1.5.3. Partial pressure during sintering Chapter 2 EXPERIMENTAL METHODS 2.1. Method of synthesized samples In this thesis, we have synthesized the following systems and investigated their structure, electromagnetic, optical and properties of these following systems: Systems was synthesized by sol-gel method SrTi 1-x M x O 3 (x = 0.0; 0.1; 0.2; 0.3; 0.4 and 0.5), including SrTi 1-x Fe x O 3 , SrTi 1-x Co x O 3 , SrTi 1-x Ni x O 3 . Systems SrTi 1-x M x O 3 films was synthesized by PLD with different contents, including SrTi 1-x Fe x O 3 films (x = 0.0; 0.1; 0.2), SrTi 1-x Co x O 3 films (x = 0.0; 0.1; 0.2; 0.3; 0.4), SrTi 1-x Ni x O 3 films (x = 0.0; 0.1; 0.2; 0.3). 2.1.1. Preparation of targets by solid phase reaction 2.1.2. Preparation of samples by sol-gel method 2.1.3. Preparation of samples by PLD method 2.2. Analysis of structure and components of samples 2.2.1. X-ray diffraction method (XRD) 2.2.2. Technique of scanning electron microscopic (SEM) 2.2.3. Atomic force microscope (AFM) 2.2.4. Analysis of component by energy dispersive spectra (EDS) 2.3. Impedance spectroscopy measurement 2.4. Magnetic measurement 2.5. Raman scattering spectroscopy measurement 2.6. Absorption spectra measurement Chapter 3 THE EFEECT OF TRANSITION METAL M (Fe, Co, Ni) SUBSTITUTION ON STRUSTURE OF SrTi 1-x M x O 3 MATERIALS 3.1. The effects of transition metal M on structure of SrTi 1-x M x O 3 synthesized by sol-gel method 3.1.1. Diagram of X-ray diffraction of SrTi 1-x M x O 3 samples Results of investigation structure of SrTi 1-x M x O 3 by X-Ray diffraction are presented in figure 3.1 On diagram of 3 systems samples, we see that diffraction peaks occurring at angles of about 32, 40, 46, 52, 57, 68 o . By comparing the diagram of X-ray diffraction pattern of pure sample with x = 0.0 with standard JCPDS 35-374 code, these peaks are in accordance with group of planes: (100), (110), (111), (200), (210), (211) và (220). Figure 3.1a presents diagram of X-ray diffraction of SrTi 1-x Fe x O 3 samples. When Fe content increases, diffraction lines change. For example, peaks of 2 - theta at 22 and 52 o disappear when substituted content reaches to x = 0.2. Especially, position of diffraction peaks shifts considerably when Fe content increases. The reason for shift may be related to the doped of Fe in Ti 4+ in lattice cells. It was known that, in octahedral, ionic radius of Sr 2+ and Ti 4+ are 1.44 Å and 0.605 Å successively. Ion Fe with different oxidation state has different ionic radius. In this thesis, our result indicates that lattice constant of SrTi 1-x Fe x O 3 decreases when Fe content increases. Therefore, it is estimated that Fe 3+ (LS) or ion Fe 4+ having smaller ionic radius substituted for ion Ti 4+ in lattice cells, leading to decrease of lattice constant. With these Fe content and heating temperature, with x = 0.2; 0.3; 0.4; 0.5, on diagram, peaks correlating with 2θ of 27.3 o occur and they are TiO 2 peaks of Rutile, with space group of P 4m/mmm . In order to limit Rutile, in careation of samples, we can replece Ti(OC 3 H 7 ) 4 with crude Ti, because when Ti(OC 3 H 7 ) 4 is diluted in water, amorphous phase TiO 2 often occurs. Figure 3.1. X-ray diffraction diagram of SrTi 1-x M x O 3 synthesized by sol-gel method: (a) SrTi 1-x Fe x O 3 , (b): SrTi 1-x Co x O 3 , (c): SrTi 1- x Ni x O 3 . Symbols presents: TiO 2 (*), TiO ( ♥ ), Ti 3 O 5 ( ♦ ), Ni ( ♠ ). 2 θ (degree) Intensity(arb.units) (210) (100) (110) (111) (200) (211) (220) 0,0 0,1 0,2 0,3 0,4 0,5 (b): SrTi 1-x Co x O 3 20 30 40 50 60 70 ♥ ♥ ∗ ♠ ♠ ♠ ♦ ∗ ♦ ♥ (c): SrTi 1-x Ni x O 3 0,5 0,4 0,3 0,2 0,1 0,0 (220) (210) (211) (200) (111) (110) (100) (a): SrTi 1-x Fe x O 3 (220) (210) (211) (200) (111) (110) (100) ∗ 0,5 0,4 0,3 0,2 0,1 0,0 Figure 3.1b present diagram of X-ray diffraction of SrTi 1-x Co x O 3 samples by sol-gel method method. The peaks shift at right low Co content (x = 0.1; 0.2) and expand when Co content rises (x = 0.3; 0.4; 0.5). Especially, at angle of lager 2θ, diffraction peaks expand and unbalance. Therefore, it is estimated that when Co content is higher, structural phase can be changed. The results of lattice constants of SrTi 1-x Co x O 3 indicate the value decreases when Co content increases. We know that ion Co can exist in many states of oxygen such as: Co 2+ , Co 3+ , Co 4+ with different ionic radius. Maybe ion Co 4+ or Co 3+ (LS) with smaller ionic radius than Ti 4+ substituted for ion Ti 4+ in crystal cells, which causes decrease in cell's size and lattice constant when Co content changes. Figure 3.1c present diagram of X-ray diffraction of SrTi 1-x Ni x O 3 samples, which shows that when substitute Ni content is low, (x = 0.1), the sample is pure and has suitable structure with pure STO. When Ni content increases to x = 0.2 and x = 0.3, contaminant phase TiO occurs (*). If Co content increases to x = 0.4 and x = 0.5, other phases such as Ti 3 O 5 (♦), TiO 2 (♥), Ni (♠) occur. Besides that, intensity of diffraction line also decreases and diffraction peaks shift to lager 2θ. Therefore, lattice constant and size of lattice cell decrease. The reason for peak shifting and constant changing may be related to substitution ion Ni for Ti 4+ in lattice cells. According to experimental condition, in substitution ion Ni 2+ for Ti 4+ in SrTi 1-x Ni x O 3 , if Ni 2+ has radius of 0.69 Å, size of cell and lattice constant will increase. We know that, like Fe and Co, ion Ni can exist in many oxidation states. In octahedral crystal, with coordination number of 6, ion Ni 3+ (HS) has radius of 0.6 Å, Ni 3+ (LS) of 0.56 Å and ion Ni 4+ only exist in HS with radius of 0.48 Å. It means that in doped with Ni in lattice cells, oxidation states of Ni 3+ và Ni 4+ predominate. 3.1.2. SEM images of SrTi 1-x M x O 3 synthesized by sol-gel method SEM images of SrTi 1-x Fe x O 3 samples show that grain size of Fe substituted samples is relative homogeneous and suitable to grain size of pure STO when Fe content increases to x = 0.3. When Fe content increases to x = 0.4; 0.5, grain size decreases to about 10-20 nm. SEM images of SrTi 1-x Co x O 3 indicate that when Co content reaches to x ≥ 0.2, grain size decreases to 10-20 nm. For SrTi 1-x Ni x O 3 samples, even when Ni content Ni reaches to x ≥ 0.1 grain size decreases considerably to only 10 nm. We see that size of crystal grain calculated by formula of Debye-Scherer is bigger than estimated size from SEM images. The reason is that in calcinations at high temperature, grains accumulate which lead to increase in size. 3.1.3. Measurement results of energy dispersive spectra (EDS) of SrTi 1- x Fe x O 3 samples synthesized by sol-gel method method. Figure 3.6 presents EDS of SrTi 1-x Fe x O 3 samples. Figure 3.6a shows that only peaks which correspond with Sr, Ti, O occur. When substituting Fe for a part of Ti, we see EDS of samples as on figure 3.2 (b-g). Besides, spectrum line of Fe also occurs at different energy level. When Fe content is of x = 0.1; 0.2, spectrum lines which are typical of Fe occur at about 0.7 and 6.2 keV. When Fe content is of x = 0.3; 0.4; 0.5, there is also another spectrum line at around 7.1 keV. In substitution Fe, intensity of spectrum peaks of Ti tend to decrease gradually and spectrum peaks of Fe tend to increase. This result is suitable to initial estimation, because when Fe content increases gradually, (from 0 to 50%), Ti content decreases ( between 100 and 50%). 3.2. Effects of transition metal ions M on structure of SrTi 1-x M x O 3 material synthesized by PLD method 3.2.1. Diagram of X-ray diffraction of SrTi 1-x M x O 3 samples synthesized by PLD method Figure 3.7 present diagram of X-ray diffraction of SrTi 1-x M x O 3 samples synthesized by PLD. Like SrTi 1-x M x O 3 samples synthesized by sol-gel method, structure of this samples are cubic of P m3m . On the diagram, diffraction peaks of pure STO film have high intensity at 2θ of about 22, 32, 40, 50 o which correspond with Muller index (100), (110), (111), (210). When substitute element and its content is different, intensity as well as diffraction peaks also change. Figure 3.7 show the XRD of Fe doped STO samples. Diagram presents x = 0.0 0.1 Fe 0.2 Fe 0.3 Fe 0.4 Fe 0.5 Fe Figure 3.3. SEM images of SrTi 1-x Fe x O 3 samples synthesized by sol-gel method [...]... METALS M (Fe, Co, Ni) ON OPTICAL PROPERTIES OF SrTi1-xMxO3 MATERIALS TO2, TO -LO2 LO1 B2g 3 (a): SrTi1-xFexO3 LO4, A2g TO4 0.0 0.1 0.2 0.3 0.4 0.5 200 400 600 800 TO3-LO2 1000 (b): SrTi1-xCoxO3 TO2, B LO1 2g Intensity (arb units) 5.1 The effects of M doped on Raman scattering spectroscopy of SrTi1-xMxO3 synthesized by sol-gel method Raman scattering spectroscopy of samples SrTi1-xMxO3 (M = Fe, Co, Ni) at... resistance value of grain local, grain boundary, (a): Sample x = 0.0 Data Fit Data Fit 15 (b): SrTi0.9Fe0.1O3 - Z (M ) '' Ω - Z (M ) '' Ω 3 2 1 0 0 2 4 6 8 10 5 0 10 0 10 20 Z' (M ) 0.8 30 40 50 Z' (ΜΩ) (c): SrTi0.8Fe0.2O3 Data Fit Data Fit (d): SrTi0.7Fe0.3O3 0.6 - Z (k ) '' Ω - Z (M ) '' Ω 45 0.4 15 0.2 0.0 30 0 1 2 0 3 50 100 150 Z' (M ) 200 Z' (kΩ) Data Fit (e): SrTi0.6Fe0.4O3 9 (g): SrTi0.5Fe0.5O3... -5000 0 5000 10000 ferroelectric properties (b): Film x= 0.1 Fe 5.0x10 4.5 Discussion of magnetic (3) responses of SrTi1-xMxO3 samples 0.0 synthesized by sol-gel và PLD method (2) Pure SrTiO3 synthesized by sol- -5.0x10 (1) gel or PLD method show both -10000 -5000 0 5000 10000 diamagnetic and ferromagnetism (c): Film x = 0.2 Fe 6.0x10 When Fe, Co, Ni content is 3.0x10 (3) small (10%), diamagnetic and... width of the band gap energy Diagram density of states indicates that, at the proximity of Fermi, electronic concentration of Oxygen 2p and Co 3d were predominant CONCLUSION 1 SrTi1-xMxO3 systems (M = Fe, Co, Ni; x = 0.0 ÷ 0.5) have been prepared by Sol-gel and PLD method The samples received by this method give good quality, satifying requirements of the investigation By sol-gel method, temperature in... (x = 0.0; 0.1; 0.2) Both pure SrTiO3 and Fe doped samples show ferroelectric 1-x x 0,5 3 0,4 0,3 0,0 0,2 0,1 x 3 M (em u/g) 1-x 1-x x 3 and diamagnetic Magnetism curve in 6.0x10 (a): Film x = 0.0 figure 4.11 presents: (1) general 3.0x10 magnetism curve, (2) diamagnetic (3) 0.0 line, (3) ferroelectric line Similarly, for SrTi1-xCoxO3 samples (x = 0.0 ÷ -3.0x10 (1) 0.4) and SrTi1-xNixO3 samples (x = 0.1;... = 0.0 ÷ 0.5) band gap energy lager When replacing ion Fe, 3d of Fe is over 2p of O on covalent band, which causes the width of band gap energy decreases This result was also affirmed by experimental and X- ray photoelectron spectrum X (XPS) Absorption (arb units) xCoxO3 By investigation of absorption spectra of SrTi1-xMxO3 samples, we can prove that the width of band gap energy decreases with Fe, Co,. .. cause decrease in band gap energy width Besides, Co, Ni exist in different oxidation states and play as acceptor which also cause decrease in band gap energy width Our estimation of energy level formation in band gap energy when doped Fe, Co, Ni in STO has been examined by density functional theory (DFT) 5.6 Electronic structure and Density of State (DOS) of Fe, Co doped SrTi1xMxO3 In this thesis, we use... TRANSITION METAL IONS M (Fe, Co, Ni) ON ELECTROMAGNETICS PROPERTIES OF SrTi1-xMxO3 MATERIALS 4.1 The effects of transition metal ions M on electronic properties on SrTi1xMxO3 synthesized by sol-gel method 4.1.1 The effects of Fe doped on electronic properties of SrTi1-xFexO3 synthesized by sol-gel method Figure 4.1 presents impedance spectroscopy of SrTi1-xFexO3 samples (x = 0.0 ÷ 0.5), from which... TO3-LO2, peak at 545 cm-1 is in accordance with mode TO4, and asymmetrical peak at 791 cm-1 is of LO4A2g oscillation In figure 5.1, Raman scattering spectroscopy of Fe, Co, Ni doped samples is different from those of pure STO sample When Fe, Co content increase (figure 5.1a, b), spectrum peaks of STO decrease and nearly disappear Raman scattering spectroscopy of SrTi1xMxO3 have strong peak at approximately... Besides, accumulation of oxides of (b) SrTi1-xCoxO3 samples, (c) SrTi1-xFe in SrTi1-xFexO3, existence of Ti NixO3 samples ( x = 0.0 ÷ 0.5) (Ti3O5, TiO2) and Ni in SrTi1-xNixO3 also cause magnetic responses For SrTi1-xCoxO3, the reason for magnetic properties are doped Co Fe, Co, Ni exist in different oxidation states, they cause different properties 4.4.2 The effects of transition metal ions M on magnetic . of SrTi 1-x M x O 3 (M = Fe, Co, Ni) system and investigation some their properties" The purpose of thesis is: (i) Preparation of SrTi 1-x M x O 3 (M = Fe, Co, Ni) systems by sol-gel. effect of transitional metals Fe, Co, Ni on electromagnetic responses and optical responses of SrTi 1-x M x O 3. STO materials doped with transition metal (Fe, Co, Ni) are not only interesting. synthesized by sol-gel method Raman scattering spectroscopy of samples SrTi 1-x M x O 3 (M = Fe, Co, Ni) at room temperature in figure 5.1. In pure STO sample, optical phonons are activate,