Study of the structural,ferroelectric,dielectric,and pyroelectric properties of the K0.5Na0.5NbO3 system doped with Li+,La3+,and Ti4+

Pure Ko.sNao sNbO3(KNN)and KNN doped with Lit(6%mole),Lat(1.66%,5%,6%mole),and Ti+t(10%mole)were prepared by mixture of oxides using high-energy milling and conventional solid-state reaction.The effects of the dopant on the physical properties of pure KNN have been evaluated based on the structural,ferroelectric,pyroelectric,and dielectric measurements.The XRD measurements show that KNN pure sample contains a mixture of monoclinic and orthorhombic crystalline phases,with a slightly higher concentration of monoclinic phase.In contrast,all doped samples show a higher concentration of the orthorhombic phase,as well as the presence of a secondary phase(K6Nb10.8O3o),also detected by Raman measurements.The samples with a higher concentration of this secondary phase,also present greater dielectric losses and lower values of remnant polarization.The dielectric measurements allowed us to detect temperatures of structural transitions(orthorhombic-tetragonal,O-T)previous to the ferroelectric paraelectric transition(tetragonal-cubic,T-C),and also in this set of samples,a direct correlation was found between the values of remnant polarization and the corresponding pyroelectric signal response.

Pyroelectric properties of 91.5Na_(0.5)Bi_(0.5)TiO_(3)-8.5K_(0.5)Bi_(0.5)TiO_(3)lead-free single crystal

The dielectric and pyroelectric performances of 91.5Na_(0.5)Bi_(0.5)TiO_(3)-8.5K_(0.5)Bi_(0.5)TiO_(3)lead-free single crystal were investigated.The depolarization temperature of the crystal is about 153°C.Among the<001>,<110>,and<111>crystallographic orientations,the<111>-oriented crystal possesses the highest pyroelectric coefficient and the largest figures of merit,and the values of p,Fv,and Fd are 5.63×10^(−4)C/m^(2)·K,0.06 m^(2)/C,and 21.5μPa−1/2 for the<111>-oriented crystal at room temperature.The Fd and Fv exhibit weak frequency dependence in the range of 100-300 Hz.With the increase of the temperature,the value of p increases,while the value of Fv decreases from 18°C to 103°C.

Dielectric response and pyroelectric properties of lead-free ferroelectric Ba_(3)(VO_(4))_(2)

The current paper presents results of dielectric response,pyroelectric behavior and conductivity study of lead-free ferroelectric barium orthovanadate(Ba_(3)(VO_(4))_(2)or Ba_(3)V_(2)O_(8))ceramic,for a wide range of temperature and frequency.An X-ray diffraction study suggests the formation of a single-phase compound in trigonal crystal system.The SEM micrograph of gold-coated pellet sample shows well-defined and homogeneous morphology.Detailed studies of dielectric parameters(ε_(r)and tanδ
)of the compound as a function of temperature and frequency reveal their independence over a wide range of temperature and frequency.The nature of Polarization versus electric field(P-E)hysteresis loop of Ba_(3)V_(2)O_(8)at room temperature suggests its ferroelectric nature.The temperature dependence of pyroelectric coefficient and figure of merits of the sample support its dielectric response.The nature of variation of dc conductivity with temperature confirms the Arrhenius and negative temperature coefficient of resistance(NTCR)behavior of the material.

Pb-DOPING EFFECTS ON THE DIELECTRIC AND PYROELECTRIC PROPERTIES OF(Sr,Pb)TiO_(3)SYSTEM

Lead strontium titanate(Sr_(1-x)Pbx)TiO_(3)(0.20≤x≤0.45,step=0.05)ceramics were prepared by conventional mixed oxide method.The X-ray diffraction patterns indicate that the prepared samples have perovskite-type structure.With the increase of Pb content,there is a tendency from the cubic to tetragonal structure.The scanning electron microscopy micrographs reveal that the addition of Pb can affect microstructure.The dependent temperature dielectric permittivity and dielectric loss were investigated in the frequency range from 100 Hz to 1MHz.The maximum peak of the dielectric permittivity versus temperature curve was broadened and a frequency dispersion of the dielectric permittivity was observed for the(Sr_(0.8)Pb_(0.2))TiO_(3)ceramics.The results obtained at the frequency of 10 kHz reveal the Curie temperature linearly increased with the lead content.Thefitted curves of temperature versus inverse dielectric permittivity at 10 kHz for(Sr_(1-x)Pbx)TiO_(3)ceramics are consistent with Curie-Weiss law.The Pyroelectric properties were also investigated.The high pyroelectric coe±cients andfigure of merits indicate that the SPT ceramics are potential materials for pyroelectric sensors.

Enhanced pyroelectric properties of PZT/PVDF-TrFE composites using calcined PZT ceramic powders

The effects of calcined lead--zirconate-titanate(PZT)powders on the electric properties of PZT/polyvinylidene-tifluorethylene copolymer(PVDF-TrFE)composites thick films were studied in this paper.Firstly,the PZT powders synthesized by hydrothermal method were calcined at different temperatures ranging from 300℃ to 900℃,and then the PZT/PVDF-TrFE composites films were produced by casting PZT/PVDF-TrFE suspension onto the indium-tin-oxide(ITO)-coated glass substrates.Electric properties,including dielectric and pyroelectric performances of thick films consisting of PZT powders calcined at different temperatures were tested.The highest pyroelectric cofficient obtained in the sample using 700℃ calcined PZT powders was 96μCm^(-2)K^(-1),which was 20%higher than the composites made of uncalcined powders.Additionally,the highest detectivity figure-of merit(FOM)(FD)of the composite was 1.36×10^(-5)Pa^(-1/2),which increased about 13.5%compared to the one using uncalcined powders.