Change In Lattice Constant Research Articles

Pressure-induced first-order antiferromagnetic to ferromagnetic transition in MnN

MnN systems have been widely used to investigate Mn incorporated into Ш–V compounds, which combines the spin and electron charge as promising diluted magnetic semiconductors (DMS). However, few experiments have demonstrated the magnetic transformation of MnN with lattice constant changes, although it has been mentioned many times in previous theoretical calculations. In this study, we synthesize MnN single crystal under high pressure and temperature. Furthermore, we perform high-pressure resistance, magnetic resistance and synchrotron radiation on MnN single crystal/polycrystalline and observe the first-order phase transition accompanied with antiferromagnetic (AFM) to ferromagnetic (FM) magnetic structure transition under 34 GPa. The experimental result and first-principles calculations reveal the same magnetic and structural transition of MnN in the compression process from equilibrium volume 18.2 to16 Å3. An analysis of electronic structure and magnetic interactions in terms of the Heisenberg Hamiltonian indicates a strong FM coupling in the [001] plane due to the double exchange mechanism of Mn eg orbitals. With the reduced Mn-N bond length under high pressure, the enhanced FM double exchange interactions could induce the magnetic transition from AFM to FM and subsequently lead to a structural transition from a face-centered tetragonal structure to a cubic structure. These findings provide the foundations for GaMnN or MnN layer DMS.

Observation of interfacial strain relaxation and electron beam damage thresholds in Al0.3In0.7N/GaN heterostructures by transmission electron microscopy

The structural quality of indium-rich Al0.3In0.7N grown by metal modulated epitaxy (MME), previously demonstrating x-ray diffraction (XRD) figures of merit ∼11 times better than the previous literature is investigated to explain the origin of such a large quality improvement. Four-dimensional scanning transmission electron microscope was used to map the lattice parameter near the AlInN/GaN heterojunction and indicate a 5.4% lattice constant change, suggesting 75% relaxation within ∼2 nm from the interface. Cross-sectional TEM Moiré fringes are observed at the AlInN/GaN heterointerface, indicating that there are misfit dislocations between AlInN and GaN which, while rare, have been observed for other highly mismatched In-rich III-Nitrides. The TEM measurements show regions of contrast indicating larger scale variations in strain, but defect contrast associated with dislocations and/or intrinsic basal stacking faults was minimal, indicating a good quality AlInN film and confirming prior XRD results. Significant electron beam induced damage can occur and depended strongly on operational conditions. The damage threshold current density was estimated using time-dependent TEM to be ∼5.7 A/cm2, significantly lower than from prior studies of InGaN. Damage also strongly depends on the thickness of the TEM foil examined and occurred at thicknesses greater than found for InGaN. The present study suggests that the MME technique is an excellent candidate for growing high-quality indium-rich AlInN films as compared to the traditional molecular beam epitaxy or metal organic chemical vapor deposition techniques.

Improvement of power conversion efficiency of Cu2ZnSn(S,Se)4 solar cells by Al doped CdS

In this work, we substituted Al doped CdS(CdS:Al) for CdS buffer layer of Cu2ZnSn(S,Se)4 (CZTSSe) solar cell to increase built-in field and decrease interface recombination, and studied influence of this substitution on power conversion efficiency (PCE) of CZTSSe solar cell. It is found that the PCE can be increased from 6.57% to 8.99% by substituting CdS:Al with Al doping concentration of 3.3 at% for CdS. The increased PCE is mainly attributed to increase in photogenerated current density (JL) and decrease in reverse saturation current density (J0). Mechanisms of increase in JL and decrease in J0 are suggested by analysis of influence of change of bandgap, transmission, electron density and lattice constants of CdS induced by Al doping on light intensity passing through CdS, built-in field and lattice mismatch of CZTSSe/CdS heterojunction. This strategy provides a rational design for optimizing the heterojunction of CZTSSe solar cells to achieve high efficiency.

Structural evolution of single-crystal RECrO3 (RE = Y, Eu–Lu) orthochromates

In-house X-ray powder diffraction has been employed to study the room-temperature structural evolution of orthochromate RECrO3 (RE ​= ​Y, Eu–Lu) single crystals grown by the floating-zone method with a laser-diode furnace. Structural refinements reveal an anomaly in the evolution of lattice parameters versus RE ionic radius. This anomaly occurred to the LuCrO3 single crystal and may be attributed to the disappearance of magnetostriction effect due to the loss of both spin and orbital angular moments of Lu3+ ions. Moreover, we have monitored the evolution of Bragg (0 2 0), (1 1 2), (2 0 0), and (0 2 1) peaks, which has varied in a regular basis with rare-earth ionic radius indicative of changes in lattice constants.

Thermodynamic stability of niobium-doped ceria surfaces

Ceria (CeO2) displays a profound catalytic capacity even when utilized as a stand-alone material. Catalyzed reactions by ceria could be enhanced when it is decorated with a trace content of d or f-metals. This study addresses the stability and properties of niobium incorporated ceria surfaces. Doping a trace amount of metals often alter catalytic properties of the host metal oxide. Herein, we investigate mixed Ce-Nb-O oxides with a prime focus on the surface free energy, lattice constant, as well as atomic charges and density of states. It was found that the most stable Ce-Nb-O configuration is obtained when Nb atoms supersede top-layer O atoms at highest niobium occupancy where the surface energy decreases by 0.3 eV/Å2 compared to neat ceria surface. It was also shown that the changes in lattice constants in this configuration is in accord with data obtained from X-Ray Diffraction patterns. Results from this study could be useful in fine-tuning catalytic attributes of ceria-based materials.

Near-field nano-spectroscopy of strong mode coupling in phonon-polaritonic crystals

Strongly coupled phonon polaritons in patterned polar dielectric nano-resonators give rise to the formation of hybridized energy states with intriguing properties. However, direct observation of mode coupling in these periodic nanostructures is still challenging for momentum-matching-required far-field spectroscopies. Here, we explore the near-field response of strong coupling between propagating and localized polariton modes sustained in SiC phonon polaritonic crystals (PhPCs) to reveal the evolution of Rabi splittings with the change of lattice constant in the near-field perspective. The near-field nano-spectra of PhPCs show distinct Rabi splitting near the forbidden bands of ∼16 cm−1 in the band structures. In particular, an exotic three-polariton-coupling effect is observed with three splitting peaks in the nano-spectra induced by the interaction between local monopolar modes in nano-pillars and zone-folded phonon polaritons. Furthermore, sharp dips indicating weak near-field scatterings appear in nano-spectra at the intrinsic frequencies of the monopolar modes with strong local-field enhancement, which are estimated to be bright scattering peaks intuitively. These results would inspire the dispersion engineering and characterization of coupled phononic nano-resonators for diverse nanophotonic applications.

Unraveling the Structural Instability of Li(Ni0.80Co0.15Al0.05)O2 as a Cathode Material Due to Operating a Li‐ion Battery

The change of the crystal structure for Li(Ni0.80 Co0.15 Al0.05 )O2 as a cathode material in a Li-ion battery is traced. During charging and discharging, the crystallographic change of Lix (Ni0.80 Co0.15 Al0.05 )O2 (x≈ 1.0-0.25) is confirmed with in situ X-ray diffraction, an electrochemical measurement, and the density functional theory calculation. Li atoms after cycling do not completely return to the initial state and defects in the Li-layer generate about 5%. The effect of defects in the Li-layer reveals the transformation of crystal structure and the change of lattice constants. Upon increasing the temperature, the instability of Li0.95 (Ni0.80 Co0.15 Al0.05 )O2 is clearly shown as the movement of transition metals using X-ray and neutron diffraction. The crystallographic values dramatically change upon increasing from 373 to 423 K, but linearly vary upon decreasing temperature. Furthermore, the result of the calculation demonstrates that the possible atom for mixing is Ni. The evolution of magnetic properties explicitly certifies the atomic movement that gives rise to a spin-glass state through the induction of ferromagnetism. In conclusion, defects are created in crystal structure during operation of the Li-ion battery and generate structural instability. The results provide the cause and mechanism of the degradation of cathode material in a Li-ion battery.

Surface plasmon resonance based tunable D-shaped single polarization filter at the communication band

A surface plasmon resonance based D-shaped tunable and broadband single-polarization filter is proposed. The complex propagation constants and the guided modes’ corresponding field profiles are calculated using the full-vector finite element method based COMSOL Multiphysics v5.0 software. From the simulation study, it is found that the confinement losses of the desired x-polarized mode are 0.17 dB/cm, and 0.30 dB/cm at the resonance wavelength of 1.31 µm, and 1.55 µm, respectively, while the losses for y-polarized unwanted guided mode are 736.30 dB/cm, and 573.32 dB/cm at the mentioned wavelengths, respectively. It is also evident that the proposed fiber offers a crosstalk of 625.10 dB at the wavelength of 1.31 µm, and 495.31 dB at the wavelength of 1.55 µm with the corresponding bandwidth of 490 nm and 485 nm over which the crosstalk is more than 20 dB for a fiber length of 1.0 mm. The study also underpins that the resonant peak shifts linearly with the change of lattice constant, radius of the gold-coated channel in the polished surface, and the size and the distance between the tuning air holes of the proposed filter. Hence, this filter can be a potential fit for micro-integration in optical systems.

High‐Pressure Studies of Correlated Electron Systems

Tuning the electronic properties of transition‐metal and rare‐earth compounds by virtue of changes of the crystallographic lattice constants offers controlled access to new forms of order. The development of tungsten carbide (WC) and moissanite Bridgman cells conceived for studies of the electrical resistivity up to 10 GPa, as well as bespoke diamond anvil cells (DACs) developed for neutron depolarization studies up to 20 GPa is reviewed. For the DACs, the applied pressure changes as a function of temperature in quantitative agreement with the thermal expansion of the pressure cell. A setup is described that is based on focusing neutron guides for measurements of the depolarization of a neutron beam by samples in a DAC. The technical progress is illustrated in terms of three examples. Measurements of the resistivity and neutron depolarization provide evidence of ferromagnetic order in SrRuO3up to 14 GPa close to a putative quantum phase transition. Combining hydrostatic, uniaxial, and quasi‐hydrostatic pressure, the emergence of incipient superconductivity in CrB2is observed. The temperature dependence of the electrical resistivity in is consistent with emergent Kondo correlations and an enhanced coupling of magneto‐elastic excitations with the conduction electrons at low and intermediate temperatures, respectively.

Crystal structure and octahedral deformation of orthorhombic perovskite ABO3: Case study of SrRuO3

Using density functional theory with local spin density approximation and taking SrRuO3 as an example, the crystal structure of ABO3 perovskite oxide and the rectangular deformation of the BO6 octahedron were studied. It was found that the degree of octahedral rectangular deformation of orthorhombic SrRuO3 is much larger than Jahn–Teller distortion, therefore, cannot be ignored. The lattice constant a is greater than b in SrRuO3 (as well as LaCrO3, LaGaO3, and PbRuO3) because the side length of rectangle along x direction, aoct, is larger than that along y direction, boct; and the tilting angle of the octahedron, φT, is smaller than arccos (boct/aoct). We found that in ABO3 oxide, BO6 octahedral rectangular deformation has a universality and, consequently, aoct ≠ boct. We discussed in detail the changes of lattice constants caused by rectangular deformation of the octahedron and divided orthorhombic ABO3 oxides into the following three categories: aoct ​> ​boct with a >b; aoct ​> ​boct with a <b; and aoct ​≤ ​boct with a <b. The relationship between the rectangular deformation and the rotation (tilting) angle or tolerance factor is analyzed. As the symmetry and lattice constants of SrRuO3 are rather inconsistent, we have analyzed and clarified them. The influence of rectangular deformation of the octahedron on the electronic structure and magnetic properties of SrRuO3 was also calculated using first principles.

Anomalous Blue Shift of Exciton Luminescence in Diamond.

Generally speaking, for a semiconductor, the temperature dependence of excitonic emission corresponds to that of its band gap. However, an anomalous behavior is exhibited by the excitonic luminescence of diamond where as the temperature increases (from 10 to 300 K), its indirect exciton luminescence peak displays a spectral-distinguishable blue shift, whereas the indirect band-gap absorption shows a weak red shift. According to experimental high-resolution deep-ultraviolet spectra and theoretical analysis, the weak red shift of its indirect band gap is ascribed to its large Debye temperature (ΘD ≈ 2220 K), which makes the lattice constant change comparatively little in a large temperature range, so the change of its band gap is relatively small; in this case, as the temperature rises, the thermal population of valence-band holes that moves to a high-energy state far away from the Fermi surface contributes to the macroscopic blue shift of its excitonic emission.

Fast and full spectrum sunlight photocatalysts: Fe/Co or Ni implanted multiferroic LaMnO3

New effective sunlight photocatalysts based on pure LaMnO3, La0.98Fe0.02MnO3, La0.95Fe0.05MnO3, La0.95Fe0.025Co0.025MnO3 and La0.95Fe0.025Ni0.025MnO3 nanoparticles were prepared via Pechini modified sol-gel method. The X-ray diffraction (XRD) analysis of all compositions proves the formation of LaMnO3 perovskite which possesses the rhombohedral structure. The implantation of Fe3+, Mn2+ or Ni2+ ions leads to clear changes in lattice constant of LaMnO3 lattice. The transmission electron microscope (TEM) and the scanning electron microscope (SEM) images of the synthesized powders show the formation of connected nanoparticles with high degree of porosity. Furthermore, the HR-TEM and the selected area electron diffraction (SAED) confirm the crystallinity of the synthesized particles. Pure LaMnO3, La0.98Fe0.02MnO3, La0.95Fe0.05MnO3, La0.95Fe0.025Co0.025MnO3 and La0.95Fe0.025Ni0.025MnO3 exhibit full spectrum (UV–Vis-IR) absorption with band gap energies of 0.75 eV, 0.8 eV, 0.82 eV, 0.85 eV and 0.89 eV, respectively. These blue shifts in the band gap energy can be attributed to the Burstein–Moss effect. La0.95Fe0.025Ni0.025MnO3 composition exhibits the fastest full degradation process for high concentration Congo red dye (40 ppm) in only 45 min compared to the pure one with degradation time of 120 min, all under free sunlight energy. Besides, nearly 88% of the Congo red pollutant was degraded in a short time equal to 15 min. Both La0.98Fe0.02MnO3 and La0.95Fe0.05MnO3 powders require 60 min for full degradation of Congo red dye (40 ppm). In contrast, La0.95Fe0.025Co0.025MnO3 takes as long to degrade the Congo red dye as pure LaMnO3 structure. As a result of doping and codoping, the recombination centers of the electron-hole pairs may be reduced and the lifetime of the charge pairs increased, making the photocatalytic effect more significant.

Study on Low-Frequency Band Gap Characteristics of a New Helmholtz Type Phononic Crystal

In order to solve the problem of low-frequency noise of aircraft cabins, this paper presents a new Helmholtz type phononic crystal with a two-dimensional symmetric structure. Under the condition of the lattice constant of 62 mm, the lower limit of the first band gap is about 12 Hz, and the width is more than 10 Hz, thus the symmetric structure has distinct sound insulation ability in the low-frequency range. Firstly, the cause of the low-frequency band gap is analyzed by using the sound pressure field, and the range of band gaps is calculated by using the finite element method and the spring-oscillator model. Although the research shows that the finite element calculation results are basically consistent with the theoretical calculation, there are still some errors, and the reasons for the errors are analyzed. Secondly, the finite element method and equivalent model method are used to explore the influence of parameters of the symmetric structure on the first band gap. The result shows that the upper limit of the first band gap decreases with the increase of the lattice constant and the wedge height and increases with the increase of the length of wedge base; the lower limit of the band gap decreases with the increase of the wedge height and length of wedge base and is independent of the change of lattice constant, which further reveals the essence of the band gap formation and verifies the accuracy of the equivalent model. This study provides some theoretical support for low-frequency noise control and broadens the design idea of symmetric phononic crystal.

Mechanical property enhancement of high-plasticity powder metallurgy titanium with a high oxygen concentration

High-plasticity titanium materials with high oxygen content were prepared by powder metallurgy (PM) and hot rolling, using pure Ti and ZrO2 powder as raw materials. Completely dissolved oxygen and zirconium atoms resulted in the lattice constant change, thereby increasing the strength. Although the oxygen content was up to 0.56 wt% (much higher than the oxygen threshold of 0.33 wt%), PM Ti still exhibited high plasticity. The Ti-0.5 wt% ZrO2 sample (0.43 wt% O) had UTS of 737 MPa and EL. of 28%, while the Ti-1.0 wt% ZrO2 sample (0.56 wt% O) had UTS of 824 MPa and EL. of 15%. Compared to pure Ti, the addition of 0.5 wt% ZrO2 resulted in a noticeable increase in UTS (increased by 9%) and EL. (increased by 19%). The strength-ductility trade-off dilemma of PM Ti alloy was broken. The formation of fine and equiaxed dynamic recrystallized grains may be one of the reasons that increased the ductility. The reinforcement effect of ZrO2 was calculated as 146.7 MPa/wt% ZrO2.

Tuning of the Structure and Magnetocaloric Effect of Mn1-xZrxCoGe Alloys (Where x = 0.03, 0.05, 0.07, and 0.1).

The aim of the present work is to study the influence of a partial substitution of Mn by Zr in MnCoGe alloys. The X-ray diffraction (XRD) studies revealed a coexistence of the orthorhombic TiNiSi-type and hexagonal Ni2In- type phases. The Rietveld analysis showed that the changes in lattice constants and content of recognized phases depended on the Zr addition. The occurrence of structural transformation was detected. This transformation was confirmed by analysis of the temperature dependence of exponent n given in the relation ΔSM = C·(BMAX)n. A decrease of the Curie temperature with an increase of the Zr content in the alloy composition was detected. The magnetic entropy changes were 6.93, 13.42, 3.96, and 2.94 J/(kg K) for Mn0.97Zr0.03CoGe, Mn0.95Zr0.05CoGe, Mn0.93Zr0.07CoGe, and Mn0.9Zr0.1CoGe, respectively. A significant rise in the magnetic entropy change for samples doped by Zr (x = 0.05) was caused by structural transformation.

New p-type sp-based half-Heusler compounds LiBaX(X = Si, Ge) for spintronics and thermoelectricity via ab-initio calculations

We have investigated the structural, electronic, magnetic, elastic and thermoelectric properties of the sp-based half-Heusler LiBaX (X = Si and Ge) alloys using the full-potential linearized augmented plane wave method of density functional theory. Two approaches are employed to approximate the correlation-exchange potential, namely the generalized-gradient approximation and the modified Becke–Johnson. Both compounds free of transition metals are ferromagnetic, half metallic with a large spin-flip gaps which are appropriate for Spintronic applications. Their half-metallicity is preserved under large lattice constant and pressure change which make them promising candidates for spintronic devices. The transport properties reveal high figure of merit values making these compounds great thermoelectric candidates. Moreover, the studied half-Heuslers are mechanically stable and both of them exhibit negative formation energy and cohesion which indicate the possibility of synthesizing and stabilizing these cheap and available materials. Up to date, no experimental or theoretical studies have been carried out regarding LiBaSi, while for LiBaGe, thermoelectric properties have not been investigated yet.

Structural modulation and physical properties of cobalt-doped layered La2 M 5As3O2 (M = Cu, Ni) compounds* *Projected supported by the National Natural Science Foundation of China (Grant Nos. 51922105 and 51772322), the National Key Research and Development Program of China (Grant Nos. 2017YFA0304700 and 2016YFA0300600), and the Beijing Natural Science Foundation, China (Grant No. Z200005).

We investigate the structural variation and physical properties of layered La2 M 5As3O2 (M = Cu, Ni) compound upon Co doping. It is found that the substitution of Co ion just induces the monotonous change of lattice constants without observing the anomalous kink in superconducting La2(Cu1–x Ni x )5As3O2 solid-solutions. Meanwhile, this doping barely changes As–As bond length in [M 5As3]2– subunit (±2%), being significantly smaller than 7% shrinkage of that in La2(Cu1–x Ni x )5As3O2. Therefore, the doping dependence of crystal structure exhibits similar trend with Ba1–x K x Fe2As2 without the interference of As1–As2 bonding, implying that the Co substitution for Cu/Ni is hole-doped. In terms of physical property, La2(Cu1–x Co x )5As3O2 turns into itinerant ferromagnetic metal, while La2(Ni1–x Co x )5As3O2 shows paramagnetism and suppressed structural phase transition upon Co-doping. The distinct structural variation and absence of superconductivity provide important clues to understand the effect of As–As bond in [M 5As3]2– subunit.

Removal of defects in CdO nanoparticle and rapid synthesis of CdO nanoflake using novel microwave technique to improve semiconductor device performance

Objective: The objective of this study is to synthesize CdO nanoparticle and nanoflakes both in a single way. Also the purpose of removing defects from semiconductor nanoparticles has been considered. Methods: Very small sized Cadmium oxide nanoparticles (11 – 29 nm) and nanoflakes of average size 70 nm were prepared by sol-gel process. Two solutions of 0.2M CdCl2 and 0.2M NaOH were used with a mixture of 1:2 ethylene glycol and methanol. Two different heating method of dried precipitate was adopted to observe the morphology and defect characteristics. Half of the precipitate was annealed in furnace and rest half in domestic microwave. Findings: The fcc (NaCl-type) structure has been found in the nanostructures with lattice constant varying with annealing temperature. We propose a linear relation for the change in lattice constant. HRTEM pictures show nanoflakes and hexagonal nanoparticles. The ratio curve of coincidence Doppler broadening spectroscopy (CDBS) found defect concentration reduction and agglomeration effect on microwave irradiation in place of furnace annealing. It indicated reduction of defects inside the nanoparticles. The S and W parameter revealed the chemical surroundings and momentum distribution of the vacancy clusters varying with crystallite size. Novelty: Furnace annealing and microwave irradiation showed different effect of surface strain on lattice. Microwave irradiation has been used to reduce defects inside CdO nanocrystals for potential application and coincidence Doppler broadening spectroscopy showed potential to be a very effective tool of defect characterization and electron momentum comparison. Also, this work presents how microwave radiation can be used to prepare nanoflakes and nanoparticles from same reactants without any substrate. Keywords: Domestic microwave; nanocrystals; positron annihilation; solgel processes

Mg:TiO2 alloy thin films based MOS capacitors grown on GaAs substrates

Electron beam evaporation technique is employed to synthesise TiO2, Mg0.1Ti0.9O2 and Mg0.2Ti0.8O2 thin films (TFs) grown on (100) n-type GaAs substrates. Field emission gun-scanning electron microscope (FEG-SEM) results show that the TFs have a thickness of ~225 nm. The non- contact atomic force microscopy (NC-AFM) images shows the pore volume of the TiO2, Mg0.1Ti0.9O2 and Mg0.2Ti0.8O2 TFs enhanced gradually. UV-Vis absorption measurements are performed on the samples to determine the main bandgap and defect level transition of the material. A unique modified Urbach theoretical model has been introduced to simulate the experimental absorption spectrum. The main bandgap energy of the TiO2, Mg0.1Ti0.9O2 and Mg0.2Ti0.8O2 samples are calculated to be ~3.45 eV, 3.85 eV and 4.30 eV respectively. A gradual enhancement in main bandgap transition probability and decrease in defect level transition of the material has been observed with enhanced incorporation of Mg into the TiO2 host material. X-ray diffraction (XRD) is performed, which shows a continuous change in lattice constant of TiO2 with Mg. Current (I)-voltage (V) characteristics of the TiO2, Mg0.1Ti0.9O2 and Mg0.2Ti0.8O2 Schottky devices revealed that the leakage current at −1 V was 1.28 × 10−6 A, 1.46 × 10−9 A and 2.44 × 10−10 A respectively. Capacitance (C)–voltage (V) measurements are performed on the devices at different frequencies. A theoretical simulation has been adopted by amending the delta depletion model at 1 MHz. The dielectric constant and the flat band voltage of the TiO2, Mg0.1Ti0.9O2 and Mg0.2Ti0.8O2 devices are found to be 100, 120 and 160 and 16.1 V, 14.7 V and 9.7 V respectively. Hill-Coleman’s method shows a gradual enhancement of the density of interface states (Dit) with Mg concentration. The calculated Dit value of the TiO2, Mg0.1Ti0.9O2 and Mg0.2Ti0.8O2 TF devices are ~6.16 × 1010 eV−1 cm−2, 6.44 × 1010 eV−1 cm−2 and 1.11 × 1011 eV−1 cm−2 respectively. The observed C-V hysteresis confirms an enhancement in the charge retention into the film with increasing Mg concentration, which in turn improves the memory window (MW) from ~0.36 V (at±7 V) to ~0.67 V (at±7 V) and ~0.87 V (at±10 V) to ~1.0 V (at±10 V) with sweeping voltage.

Microwave absorbing properties of La1-x Ba x MnO3 (x=0.1,0.2,0.3,0.4,0.5) nano-particles

Electromagnetic wave absorbing materials have always been a research hotspot in military and civil fields. La1-x Ba x MnO3 nanocrystalline powders were prepared by sol-gel method. XRD analysis shows that La1-x Ba x MnO3 is a single perovskite structure, and the lattice constant changes with the doping amount. SEM analysis shows that La1-x Ba x MnO3 is basically spherical with an average particle size of about 80 nm. The relationship between the complex permittivity and permeability with microwave frequency was measured by microwave vector network analyzer. According to the measured data, the microwave reflectivity and loss factor of the sample were calculated, and the microwave loss mechanism of the sample was discussed. The results show that x has a great influence on the absorbing properties of La1-x Ba x MnO3. When x is 0.2 and the thickness is 1.6mm, the absorption bandwidth above 10dB reaches 2.1GHz and the maximum absorption value is 25dB. The microwave loss of La1-x Ba x MnO3 mainly comes from the dielectric polarization loss of perovskite materials, it also comes from conductivity loss, magnetic loss and interface polarization loss due to Ba doping and nano effect.