Submitted by IDALCI CRUVINEL DOS REIS null (idalcireis@yahoo.com.br) on 2016-01-27T19:12:31Z No. of bitstreams: 1 Tese_Idalci Cruvinel dos Reis.pdf: 11534800 bytes, checksum: bebcb1750beb5d5066bead83c37b196a (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-01-28T18:47:45Z (GMT) No. of bitstreams: 1 reis_ic_dr_ilha.pdf: 11534800 bytes, checksum: bebcb1750beb5d5066bead83c37b196a (MD5) / Made available in DSpace on 2016-01-28T18:47:45Z (GMT). No. of bitstreams: 1 reis_ic_dr_ilha.pdf: 11534800 bytes, checksum: bebcb1750beb5d5066bead83c37b196a (MD5) Previous issue date: 2015-12-18 / Fundação de Amparo à Pesquisa do Estado de Goiás (FAPEG) / Neste trabalho, as características estruturais, microestruturais, ferroelétricas e dielétricas de materiais ferroelétricos com estruturas laminares de bismuto (BLSFs), conhecidos como Aurivillius, foram investigadas. Os sistemas objetos de estudo foram compostos bicamadas (SrBi2Nb2O9, SrBi2Ta2O9, BaBi2Nb2O9) e tricamadas (Bi4Ti3O12), onde foi considerada a dopagem do sítio A da estrutura com lantânio (La3+). As propriedades físicas, portanto, foram investigadas considerando a influência do La3+ para várias concentrações. As cerâmicas foram preparadas pelo método de reação de estado sólido com sinterização em temperaturas acima de 1000 °C, para todos os casos. Para o estudo das propriedades estruturais e microestruturais, foram utilizadas as técnicas de difração de raios-x, Espectroscopia Raman, Microscopia Eletrônica de Varredura (MEV) e Espectrometria de Dispersão de Energia (EDS). As propriedades ferroelétricas e dielétricas foram investigadas a partir da dependência da polarização com o campo elétrico e resposta dielétrica com temperatura, respectivamente. Fases puras foram verificadas para todos os sistemas e analisadas com refinamento pelo método de Reitveld. Os resultados apresentaram indícios de alterações nas estruturas das cerâmicas, o que pode ser associado à influência do lantânio na estrutura. Essas alterações foram confirmadas nas medidas de MEV, onde foi possível observar um aumento significativo dos tamanhos médios dos grãos com aumento do dopante para os sistemas bicamadas e uma redução para o sistema tri-camadas. As medidas de Raman identificaram os modos ativos característicos dos sistemas Aurivillius para todos os sistemas estudados, com influência do conteúdo de lantânio na estrutura. As propriedades ferroelétricas foram confirmadas para todos os casos com uma pequena contribuição da condutividade, que pode ser a causa da obtenção de ciclos de histerese aquém da saturação para alguns casos. Em particular, o sistema SrBi2Ta2O9 revelou ciclos bem característicos e definidos, enquanto o sistema BaBi2Nb2O9 mostrou o comportamento esperado para os ferroelétricos relaxores. Picos bem definidos foram observados na resposta dielétrica para todos os casos, observando uma forte influência do conteúdo de dopante nos parâmetros dielétricos. As características da transição de fases revelam comportamentos associados tanto a um ferroelétrico normal quanto ao comportamento típico de relaxores. Este efeito foi discutido detalhadamente para cada caso. É importante destacar que, para todos os casos, baixos valores de perdas dielétricas foram obtidos, muito abaixo dos reportados na literatura para sistemas Aurivillius. Diante destes resultados, os sistemas aqui estudados são fortes candidatos para aplicações tecnológicas. / In this work the structural, microstructural, ferroelectric and dielectric characteristics of ferroelectric materials with bismuth layer structures (BLSFs), known as Aurivillius, were investigated. The studied materials were based on bi-layers (SrBi2Nb2O9, SrBi2Ta2O9, BaBi2Nb2O9) and tri-layer (Bi4Ti3O12) systems, where the lanthanum (La3+) doping in the A-site of the structure has been considered. The physical properties where, therefore, investigated considering the influence of La3+ at various concentrations. The ceramics were prepared by the solid state reaction method for temperatures above 1000 °C for all the cases. For the investigation of the structural and microstructural properties the x-ray diffraction technique, as well as Raman spectroscopy, Scanning Electron Microscopy (SEM) and Energy Dispersive of Spectrometry (EDS) were used. The ferroelectric and dielectric properties were investigated from the electric field dependence of the polarization and dielectric response with temperature, respectively. Pure phases were found for all the systems and analyzed with structural refinement by the Reitveld’s method. The results showed changes in the structure of the ceramics, which can be associated with the influence of the lanthanum content in the structure. These changes were confirmed in the SEM measurements, where a significant increase in average grain size with the increase of the doping content for bi-layer systems, as well as a reduction in average grain size for the tri-layer system, has been observed. The Raman measurements showed the characteristic bands of the Aurivillius systems, with influence of the lanthanum content in the structure, for all the cases. The ferroelectric properties were confirmed in all cases, with a small contribution of the conductivity, which can be the cause for the observation of unsaturated loops in some cases. Particularly, the SrBi2Ta2O9 system showed very well defined hysteresis loops and the BaBi2Nb2O9 system showed the expected behavior for relaxor ferroelectrics. On the other hand, well defined peaks were observed in the dielectric response for all cases, showing a strong influence of the dopant content in the dielectric parameters. The phase transition characteristics revealed behaviors associated with both normal and relaxor ferroelectrics. This effect has been discussed in details for all the cases. Very low values of the dielectric losses were found, when compared to those reported in the literature for typical Aurivillius systems. This result makes the materials studied here promissory systems for practical applications. / FAPEG: 201310267000048

No description available.

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / No presente trabalho investigamos as propriedades do composto multiferrÃico Bi5FeTi3O15 (BFTO) em funÃÃo da temperatura e pressÃo atravÃs das tÃcnicas de espectroscopia Raman e infravermelho (IR). Os modos Raman observados em baixa frequÃncia estÃo relacionados com os Ãtomos de Bi no sÃtio A. Os modos em alta frequÃncia estÃo relacionados à deformaÃÃo e estiramento dos octaedros (Ti/Fe)O6. A anÃlise do espectro a baixas temperaturas mostrou que os modos nÃo apresentam mudanÃas em seu comportamento exceto por uma tendÃncia a degenerescÃncia apresentada pelo material devido à agitaÃÃo tÃrmica. TambÃm foi possÃvel observar que o antiferromagnetismo à estÃvel e mantido pela interaÃÃo spin-fÃnon. O espectro Raman em funÃÃo de altas temperaturas mostrou divergÃncia em relaÃÃo aos resultados reportados na literatura anteriormente, bem como uma transiÃÃo de fase intermediÃria por volta de 800 K evidenciada pelo comportamento soft mode do modo em 27cm-1. Os espectros Raman em funÃÃo da pressÃo sugerem que o BFTO sofre transiÃÃes de fase em torno 1,0 GPa, 2,0 GPa, 3,0 GPa, 7,5 GPa e 10,5 GPa. / In this work we investigate the properties of the multiferroic compound Bi5FeTi3O15 (BFTO) as a function of temperature and pressure using Raman and infrared (IR) spectroscopy. The Raman modes observed show that the low-frequency bands are related to the Bi atoms in A sites. The high-frequency modes are related to the bending and stretching of the (Ti/Fe)O6 octahedra. The analysis of the low-temperature spectra showed that the modes do not present changes in their behavior except for a tendency to degeneration due to thermal agitation. Also, it was possible to observe that the antiferromagnetism is stable and maintained by a spin-phonon interaction. The Raman spectra at high-temperatures showed deviation in relation to the results reported in the literature and an intermediate phase transition around 800 K as evidenced by a soft mode behavior of the mode at 27 cm-1. The Raman spectra as a function of pressure suggest that BFTO undergoes phase transitions around 1.0 GPa, 2.0 GPa, 3.0 GPa, 7.5 GPa and 10.5 GPa.

Bismuth layer-structured ferroelectrics have received significant attention recently due to their fairly high TC and good fatigue endurance which make them important candidates for non-volatile ferroelectric random access memories (Fe-RAMs) as well as for the piezoelectric device applications at high temperatures. Structure of these compounds is generally described as the pseudo-perovskite block (An-1BnO3n+1)2- sandwiched between the bismuth oxide layers (Bi2O2)2+ along the c-axis, where n represents the number of corner sharing BO6 octahedra forming the perovskite-like slabs. Only a few compounds belonging to this family show relaxor behavior (frequency dependent diffuse phase transition). Relaxor ferroelectrics are very attractive for a variety of applications, such as capacitors, sensors, actuators, and integrated electromechanical systems. The present work attempts to understand the mechanism of relaxor behavior in Aurivillius oxides as well as to improve the piezoelectric and ferroelectric properties of some of the known phases. Details pertaining to the fabrication and characterization of BaBi4Ti4O15 (n = 4 member of Aurivillius family of oxides) ceramics are presented. X-ray diffraction, Raman spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) were employed to probe the structural and microstructural details. The contribution of irreversible domain wall movement to the room temperature dielectric constant and polarization was quantitatively evaluated using the nonlinear dielectric response. Dielectric dispersion and conduction mechanism of these ceramics are also explicated using the complex impedance spectroscopy. The effects of La3+ and Ca2+ doping on the phase transition behavior and other properties of BaBi4Ti4O15 are investigated. La3+ doping for Bi3+ was found to strengthen the relaxor behavior. New compounds such as CaNaBi2Nb3O12, SrNaBi2Nb3O12, Na0.5La0.5Bi4Ti4O12, etc. belonging to the Aurivillius family of oxides have been synthesized and investigations concerning their structural, dielectric and ferroelectric properties are presented. Rietveld refinement of room temperature X-ray powder data suggested that CaNaBi2Nb3O12 and SrNaBi2Nb3O12crystallize in the orthorhombic space group B2cb. SrNaBi2Nb3O12 ceramics exhibited frequency-dependent Tm which follows the Vogel-Fulcher relation implying a relaxor nature. No frequency dependence of Tm was observed for CaNaBi2Nb3O12 ceramics. Polarization - electric field hysteresis loops recorded well above Tm confirmed the coexistence of polar and non-polar domains in SrNaBi2Nb3O12 ceramics. Dielectric anomaly observed around 675 K for CNBN corresponds to the ferroelectric to paraelectric phase transition which is accompanied by the change in crystal structure from orthorhombic to tetragonal. Fe and Nb co-doped Bi4Ti3O12 ceramics were fabricated and characterized for their structural, electrical and magnetic properties.

Materials chemistry is essentially concerned with the design/synthesis of new solids endowed with functional properties that could be of relevance to today’s materials technology. Among the large variety of solid materials that attract attention, metal oxides continue to contribute significantly to current materials chemistry. A wide variety of oxide materials (based on rocksalt, spinel, corundum, perovskite, garnet, pyrochlore and other structures) and their properties have been investigated over the years. Most of these oxides are derived from the transition metals. Transition metal oxides with structures derived from metal-oxygen (MO6) octahedra, in particular, display an array of exotic properties with potential or proven technological application. While it is traditionally believed that the partially filled d shell (dn : 0 < n < 10) of the transition metal atoms plays a crucial role in deciding the electronic properties, the significance of d0 metal atoms for the properties (and structure) of transition metal oxides is not fully recognized. Magnetism (SrRuO3, Fe3O4), metallicity (ReO3, LaNiO3), colossal magnetoresistance (La1-xCaxMnO3) and superconductivity (La2xSrxCuO4, Sr2RuO4) are some of the properties that can be traced to the presence of partially filled d shell, while properties like ferroelectricity (BaTiO3), piezoelectricity (PbZr1-xTixO3) and nonlinear optical response (LiNbO3) could be traced to the presence of transition metals (TiIV, ZrIV, NbV) with d0 electronic configuration. The empty d orbitals on the metal atoms constitute the low lying unoccupied states (LUMO) that mix with the highest occupied states (HOMO) of the ligand atoms (oxygen) through special chemical bonding effects (second order Jahn-Teller effect, SOJT). This mixing results, among others, in out-of-centre distortion(s) of the MO6 octahedra and this distortion is at the heart of several properties mentioned above. Among the transition metal oxide structures based on MO6 octahedra, three structures are noteworthy: the perovskite, the pyrochlore and the rutile. The AMO3 perovskite structure consists of a three-dimensional framework of corner sharing MO6 octahedra in which the A cation occupies the dodecahedral site surrounded by twelve oxide ions. The perovskite structure can accommodate a large variety of substitutions at both the A and the M sites as well as vacancies at the A/O sites, giving a large number of derivatives. Several variants of the perovskite structure are also known, for instance, the layered perovskites and ordered perovskites. Many nonperovskite structures are also known for the composition AMO3 : hexagonal YMnO3 is an alternative structure for AMO3 composition where manganese exists as MnO5 trigonal bipyramids. The A2M2O7 pyrochlore structure is also based on a corner-connected network of MO6 octahedra which interpenetrates an A2O network. The rutile (TiO2) is a well-known structure consisting of chains of edge-sharing MO6 octahedra, which are connected through corners to adjacent chains. A large number of oxide materials based on the above three structure types have been reported : for example, perovskite [Ba3ZnTa2O9 (microwave telecommunication ceramic), Pb3MgNb2O9 (relaxor ferroelectric), Bi4Ti3O12 (high temperature ferroelectric)], pyrochlore [Nd2Mo2O7 (metallic ferromagnet), AOs2O6 for A = K, Rb, Cs (superconductor)] and rutile [TiO2 (photocatalyst), CrO2 (metallic ferromagnet), VO2 (insulator-metal transition)]. Considering the current interest in oxide materials of these three structure types which continue to generate new variants and novel properties, we undertook the present research project to synthesize new derivatives of these structure types, and characterize their structures and relevant electronic properties. In doing so, we recognized that synthesis based on an understanding of the reactivity of the constituents and crystal chemistry of the expected products plays a crucial role in this effort. Accordingly, we tailored several new compositions of AMO3, A2M2O7 and MO2 stoichiometries and adopted appropriate methodologies for their synthesis. We have characterized the structures and properties of the solid products by means of state-of-the-art methods available to us. There are two main approaches to the synthesis of nonmolecular inorganic solids: conventional ceramic route and chimie douce / soft chemistry routes. In the ceramic route, solid reactants are heated at elevated temperatures for long durations with intermittent mixing/grinding until the reaction is complete. Chimie douce routes, on the other hand, utilize gentle reactions such as dehydration, decomposition, intercalation, ion exchange, and so on to synthesize the desired phases. The ceramic route generally provides access to the thermodynamically controlled product(s), while chimie douce routes allow access to metastable phases (kinetically controlled product(s)). Disadvantages notwithstanding, the ceramic route has been the mainstay of materials chemistry and several important materials continue to be discovered / synthesized by this route. The choice of the synthetic route based on an understanding of the crystal chemical preferences and the reactivities of the constituents involved is often crucial to achieve the desired final products. The present thesis is devoted to the synthesis and investigation of MO6 octahedra-based oxides belonging to the perovskite, pyrochlore and rutile structure types wherein we have explored alternate synthetic strategies (perovskite-based Ba3MM'2O9 telecommunication ceramics and a solution route for the synthesis of ruthenium-based pyrochlores) and probed structure-property relations of perovskite oxides (Ba3MM'M''O9 oxides for various M/M'/M'' atoms) as well as formation of new derivatives of layered Aurivillius phases. In addition, we have also synthesized new noncentrosymmetric oxides possessing the YMnO3 structure. Our investigation of rutile based oxides has resulted in the discovery of a new lead-free relaxor ferroelectric material, FeTiTaO6. Given that the lone pair PbII:6s2 plays a crucial role in the ferroelectric properties of Pb-based perovskite oxides, we have also investigated members of the Pb1-xLix/2Lax/2TiO3 system for their structure and dielectric response. The present thesis describes the results of these investigations in eight chapters. Chapter 1 provides a general introduction to oxides of the perovskite, pyrochlore and rutile structures. In Chapter 2, we describe a new one-pot metathesis strategy for the synthesis of dielectric ceramics Ba3MM'2O9 (M = Mg, Ni, Zn; M' = Nb, Ta). Rietveld refinement of X-ray diffraction data shows near-complete ordering of M-site ions in many cases. The dielectric properties of the products synthesized are found to be in reasonable agreement with reported data. The synthesis of ordered materials at lower temperatures (~1100 °C) than that employed in the conventional ceramic route (~1500 °C) is a significant result of this work. Chapter 3 presents a study of Ba3MIIMIVWO9 (MII = Ca, Zn; MIV = Ti, Zr) perovskite oxides for the purpose of synthesizing new dielectric ceramic materials and to gain understanding of the factors that stabilize 3C vs. 6H structures. In general, a 1:2-ordered 6H perovskite structure is stabilized at high temperatures (1300 °C) for all of the Ba3MIITiWO9 oxides investigated. An intermediate phase possessing a partially ordered 1:1 double perovskite (3C) structure with the cation distribution, Ba2(Zn2/3Ti1/3)(W2/3Ti1/3)O6, is obtained at 1200 °C for Ba3ZnTiWO9. A metastable perovskite, Ba3CaZrWO9, that adopts the 1:1 3C structure has also been synthesized by a low-temperature metathesis route. Besides yielding several new perovskite oxides that may be useful as dielectric ceramics, the investigation provides new insights into the complex interplay of crystal chemistry (tolerance factor) and chemical bonding (anion polarization and d0-induced distortion of metaloxygen octahedra) in the stabilization of 6H versus 3C perovskite structures for the Ba3MIIMIVWO9 series. In Chapter 4, we describe the synthesis and investigation of the structure and dielectric properties of Ba3MIIITiMVO9 (MIII = Fe, Ga, Y, Lu; MV = Nb, Ta, Sb) perovskite oxides. The MV = Nb, Ta oxides adopt disordered/partially ordered 3C perovskite structures, where all the MIII/Ti/MV metal-oxygen octahedra are corner-connected. In contrast, the MV = Sb oxides show a distinct preference for the 6H structure, where SbV/TiIV metal-oxygen octahedra share a common face, forming (Sb,Ti)O9 dimers, that are corner-connected to the MIIIO6 octahedra. Investigation of dielectric properties of MIII = Y/Lu, MV = Nb/Ta oxides reveals a normal low loss dielectric behaviour with ε = 30 – 50 in the temperature range 50 – 350 °C. The MIII = Fe, MV = Nb/Ta members show a dielectric behaviour similar to relaxor ferroelectric materials. Chapter 5 deals with a study of isomorphous substitution of several metal atoms in two Aurivillius structures, Bi5TiNbWO15 and Bi4Ti3O12, in an effort to probe structure-property correlations. These investigations have led to the synthesis of new derivatives, Bi4LnTiMWO15 (Ln, = La, Pr; M = Nb, Ta), as well as Bi4PbNb2WO15 and Bi3LaPbNb2WO15, that largely retain the Aurivillius intergrowth structure of the parent oxide Bi5TiNbWO15, but characteristically tend toward a centrosymmetric / tetragonal structure for the Ln-substituted derivatives. On the other hand, coupled substitution, 2TiIV Æ MV + FeIII in Bi4Ti3O12, yields new Aurivillius phases, Bi4Ti3-2xNbxFexO12 (x = 0.25, 0.50) and Bi4Ti3-2xTaxFexO12 (x = 0.25) that retain the orthorhombic noncentrosymmetric structure of the parent Bi4Ti3O12. Chapter 6 describes the design and synthesis of a new series of noncentrosymmetric oxides, R3Mn1.5CuV0.5O9 (R = Y, Ho, Er, Tm, Yb, Lu) possessing the YMnO3 structure. Investigation of the Lu-Mn-Cu-V-O system revealed the existence of an isostructural solid solution series, Lu3Mn3-3xCu2xVxO9 for 0 < x ≤ 0.75. Magnetic and dielectric properties of the oxides are consistent with a random distribution of Mn3+, Cu2+ and V5+ atoms that preserves the noncentrosymmetric RMnO3 structure. An exploratory investigation of the synthesis, structure and electronic properties of new ruthenium(IV) pyrochlore oxides and their manganese-substituted derivatives is presented in Chapter 7. The richness of the electronic properties of ruthenium-based metal oxides is affirmed by the results which revealed several novel electronic ground states : a metallic and Pauli paramagnetic state for BiPbRu2O6.5 that turns into a semiconducting ferromagnetic spin-glass state at 50 K for BiPbRuMnO6.5 ; a metallic state that likely shows a charge density wave (CDW) instability at 50-225 K for Bi1.50Zn0.50Ru2O6.75, that is suppressed by manganese substitution in Bi1.50Zn0.50Ru1.75Mn0.25O6.50, and a metallic ferromagnetic spin-glass-like state for Pb2Ru1.75Mn0.25O6.15. We describe the investigation of the structure and dielectric properties of rutile-based MTiTaO6 (M = Al, Cr, Fe) in Chapter 8. All the oxides possess disordered rutile structure. FeTiTaO6 shows a strong relaxor ferroelectric effect, while CrTiTaO6 shows a weaker relaxor ferroelectric behaviour. This work is significant for two reasons: the new material is lead-free and it is based on the rutile structure, unlike the conventional relaxors which are mostly derived from the perovskite structure. The work presented in the thesis is carried out by the candidate as a part of the Ph.D. training programme and most of it has been published in the literature. She hopes that the studies reported here will constitute a worthwhile contribution to materials chemistry in general.

Relaxor ferroelectrics have been a subject of intense research owing to their interesting physical properties such as high dielectric constant and giant electro-striction. Unlike the conventional lead based relaxors, the relaxors belonging to Aurivillius family of oxides have received much less attention because of the poor understanding of the origin of the relaxor behavior and high processing temperatures involved. In the present investigations, an attempt has been made to understand the origin of relaxor behavior of the materials belonging to Aurivillius family of oxides. The structure and relaxor behavior of BaBi2Nb2O9 (BBN) has been established via the XRD, electron diffraction and dielectric spectroscopy. The results are compared with that of a normal ferroelectric like SrBi2Nb2O9 belonging to the same family as well with that of a conventional relaxor like PMN. The results indicate that the dielectric behavior of BBN is significantly different from that of the conventional relaxors like BBN with very slow broadening of relaxation times and was attributed to the absence of significant polar ordering. To substantiate the existing understanding, studies have been carried out by adopting different strategies such as B-site and A-site cationic substitutions and texturing of the ceramics. Vanadium doping on B-site was found to decrease the sintering temperatures significantly. Aliovalent La3+ doping was found to affect the dielectric behavior strongly with substantial decrease of the freezing temperature and dielectric constants which shows that the relaxor behavior of BBN is highly sensitive to A-site order-disorder. The (00l) textured ceramic of pure and vanadium doped BBN was fabricated via a simple melt-quenching technique and was found to exhibit a significant dielectric and pyroelectric anisotropy. A new class of relaxor compositions (K0.5La0.5Bi2Nb2O9 & K0.5La0.5Bi2Ta2O9) have been synthesized and characterized. These new compounds exhibited interesting physical properties which are akin to that of the conventional lead based relaxors. The presence of superlattice reflections in the electron diffractin patterns recorded on these compounds establish the presence of polar nano regions of significant size. These relaxor crystallites at nano/micro level embedded in a glass matrix have been found to be very promising from their physical properties view point.

No description available.

The present research work mainly focuses on the fabrication and characterization of single and multilayer thin films based on Bismuth Vanadate (BVO) and Bismuth Titanate (BTO). The multi-target laser ablation technique was used to fabricate single layer thin films of BVO, BVN and BTO; and multilayers composed of BVO and BTO in different structures. The fabricated thin films exhibited dense microstructure and a sharp interface with the substrate. The lattice strain, surface roughness and grain size could be varied as functions of composition and individual layer thickness in different structure fabricated. The optical properties were studied by spectroscopic ellipsometry and optical transmission spectra. The various models that were used for ellipsometric data analysis gave an excellent fitting to the experimental data. The optical constants were determined through multilayer analyses of the films. The band gap of these films was studied by spectroscopic ellipsometry and optical transmission. The optical studies carried out on BVO-BTO bilayer indicated the presence of an interfacial layer in between the BVO and BTO layer, whose refractive index was different from that of the individual layers and is attributed to different nature of the interfacial layer. The ferroelectric nature of BVO films was confirmed by P-E hysteresis loop studies under different applied fields and at various probing frequencies. The same was corroborated via the C-V measurements of these BVO films which exhibited butterfly shaped C-V characteristics. Fatigue studies in these films indicated that the switchable polarization is essentially constant through 105 cycles, after which it starts increasing probably due to the ionic conduction in BVO thin films. The dielectric response of undoped and Nb doped BVO as well as BVBT ML thin films were studied over a wide range of temperatures. The BVO films exhibited remarkable dielectric dispersion at low frequencies especially in the high temperature regime. Further, the frequency and temperature dependence of the dielectric, impedance, modulus and conductivity spectra of these films were investigated in detail. The ac conductivity was found to obey well the double power law in case of ML, indicating the different contributions to the conductivity, the low frequency conductivity being due to the short range translational hopping and the high frequency conductivity is due to the localized or reorientational hopping motion. DC leakage conduction in BVO, BVN and BVBT ML thin films was studied over a wide range of temperatures and applied electric fields. The experimental data were analyzed in light of different models to investigate the dc conduction mechanism in these films which were broadly classified into electrode limited and bulk limited conduction processes. In the case of BVO thin films the dc leakage current exhibited an ohmic nature at low electric fields followed by an onset of the space charge limited conduction (>1). Further in case of BVN films, three distinct regions were observed in I-V characteristics signifying different types of conduction processes in these films. In case of BVBT ML thin films, bulk limited PF mechanism was found to determine the conduction behavior at moderate electric fields. At higher electric fields, a trap filled region was observed which was followed by SCL conduction at higher fields. Therefore the present observation indicates the presence of more than one bulk limited conduction process in BVBT ML thin films. BVO thin films exhibiting good structure and dense morphology were successfully prepared on p-type Si by chemical solution decomposition technique. The C-V characteristics were evaluated for Au/BVO/Si MFS structure which showed a typical high frequency feature of a conventional MFIS structure.