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It is well established that calcium phosphate can be a self-activated photoluminescent agent via lattice water removal-induced intrinsic defects, whose luminescence intensity can be further enhanced in terms of the amorphous state. Inspired by these facts, self-activated photoluminescent amorphous magnesium phosphate (MgP) was synthesized via microwave irradiation and thermal processing, along with calcium magnesium phosphate (CaMgP) and calcium phosphate (CaP) for comparisons. The relevant fluorescence imaging and transient steady-state fluorescence spectrometer tests revealed that the fluorescence performance of the as-formed particles increased in the order of CaP, CaMgP, and MgP. This phenomenon was attributed to the difference in structural water loss among these particles during thermal processing, in which the three tested materials experienced weight losses of 10%, 19%, and 25% when heated to $400^{\circ }$C. Despite this, when amorphous MgP was heated up to 200, 300, and $400^{\circ }$C, its photoluminescence emission intensity also increased. The impact of the pH of the precursor solution was also studied, paving the way for further improving MgP’s photoluminescence properties.

This paper discusses ways to search for lead-free functional materials for various applications. Using the example of the solid solution systems based on alkali metal niobates, the influence of the position on the phase diagram of the corresponding systems, the number of the components in them, and modification with mono- and combined metal oxides on their characteristics is shown. It has been established that the most effective in terms of piezoelectric characteristics are the solid solution systems in or near the morphotropic region, with 3 or 4 components. A number of materials have been developed to create highly sensitive electromechanical transducers, ultrasonic delay lines and other applications.

The results of an investigation of humidity sensors based on ceramic material are discussed. It is widely approved that the ceramics based humidity sensor is superior to the polymer one due to their better thermal stability over a variety of chemical species, wide range of operating temperature and rapid response to change of humidity. Properties of humidity sensor based on ceramic system Ca_1-xY_xTi_1-xCo_xO₃ are presented. The role of each part of the sensitive material in the electrical conduction process is determined based on measurements and calculated equivalent circuits. The proposed model describes the water absorption on grain and grain boundaries surfaces with very good fit to the experimental data. A new approach to the modeling of the impedance frequency dependence by means of an equivalent circuit yields very promising results for sensors.

Pb_0.76-3x/2La_xCa_0.24Mn_0.02Ti_0.98O₃ (PLCT), x=0–0.08 (in steps of 0.02), ceramics were prepared by conventional mixed oxide technique. The samples were sintered at an optimized temperature of 1150°C. Phase and microstructural analysis were carried out using X-ray Diffraction (XRD) and scanning electron microscope (SEM) to study the effect of lanthanum on PCT ceramics. Both experimental and theoretical densities for all the samples were also determined. Phase analysis shows the single-phase material with tetragonal structure and the decrease in tetragonality is observed with the increase in the amount of lanthanum in the base composition. Detailed dilatometric investigations were performed in order to study the shrinkage behaviour and dominating shrinkage mechanism in the present system.

Tribological experiments were conducted on a ball-on-disk, unlubricated, with a speed of V≈ 140mm/s, V≈ 70mm/s, with an applied load between 20 and 100N, and with different combinations of ceramic materials. A wear test was conducted on disk material zirconia with regard to various ceramic ball materials (zirconia, alumina, silicon carbide and silicon nitride). The results show that the properties of the counter materials cause a difference in friction and wear characteristics.

We have systematically studied the X-ray radiation effects on PZT thin ceramic disk provided by CTS Communications Components, Inc using the X-ray beam line in the Center for Advanced Micro-Structure and Devices (CAMD) in Baton Rouge, Louisiana. The photo energies of the X-ray range from 2000 eV to 8000 eV. The beam size is 10.0cm×1.0cm.We measure the dielectric constant in situ with different dose of the radiation in one sample and in different samples. The dielectric constants as a function of radiation dose are presented in the paper. It demonstrates the effects on the dielectric constant. Unexpectedly, we also found that X-ray radiation on the PZT disk generates charges on the surface of the samples. We measured the surface voltage due to the X-ray radiation with different radiation dose at the same temperature for these samples. This founding may have application potential for photoelectric devices. This is just a preliminary study. More thorough investigations are needed.

Two kinds of theory for non-destructive inspection of ceramics were reviewed, which were derived by the authors using flaw-size distribution. In the sufficient condition theory (Realistic NDI), we had discussed about the screening flaw-size and a screening region. In the necessary and sufficient condition theory (Ideal NDI), we found that the screening flaw-size should be changed depending on stress state and specimen configuration. It was proved that there is one-to-one correspondence between Ideal NDI and a proof test. Applications to machining damage problems and surface strengthening of ceramics were also presented.

Compositions with x=0.1, 0.2, 0.4, and 0.5 in the system (Pb_0.95Sr_0.05)·(Zr_0.53Ti_0.47)O₃+xwt%Cr₂O₃ (PSZTC) were synthesized using conventional ceramic method. Addition of Cr₂O₃ stabilized the tetragonal phase against the rhombohedral one. Scanning electron microscopy (SEM) showed a decrease of the mean grain size when increasing the doping level. The permittivity and electrical conductivities of the PSZTC compounds have been investigated and the activation energies were calculated.

Pure nanocrystalline forsterite (Mg₂SiO₄) powder was successfully synthesized by mechanochemical route and subsequent annealing. The starting materials were talc (Mg₃Si₄ O₁₀(OH)₂) and magnesium carbonate (MgCO₃) powders. To produce forsterite powder, first talc and magnesium carbonate powders were calcined at 1200°C for 1 h and 700°C for 2 h, respectively. After that the mixture of obtained powders was milled by a planetary ball mill, and then annealed at 1000°C and 1200°C for 1 h. Thermogravimetric (TG) analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM) techniques were utilized to characterize the initial and prepared powders. The results showed that a single phase nanocrystalline forsterite powder with a crystallite size of 49 nm was obtained after 40 h milling and subsequent annealing at 1000°C for 1 h.

Samples of CaCu₃Ti₄O₁₂ (CCTO) ceramics were prepared by solid state reaction method. X-ray diffraction analysis confirmed single phase formation for the powder calcined at 1173 K. Sintering was done at different temperatures viz. 1348 K, 1373 K and 1398 K with a fixed heating rate of 3 K/min. Detailed study of dielectric properties was carried out for the CCTO samples sintered at 1373 K for different duration of holding times (2 h and 10 h). It is found that dielectric properties are sensitive to both sintering time and temperature. With increasing sintering time from 2 h to 10 h dielectric constant increases from ∼2.1 × 10⁴ to ∼2.5 × 10⁴ measured at 1 kHz at room temperature. Impedance spectroscopy has been used for separating out of grain and grain boundary contributions to the overall electrical properties.

Solution-based chemical method was used to prepare the compound LiCoVO₄. Compound formation was checked by X-ray diffraction (XRD) study and it revealed a cubic unit cell structure with lattice parameter: a = 8.2840 (3) Å. Complex impedance result shows bulk contribution to electrical properties up to 225°C, grain boundary effects for all T ≥ 250°C, and evidence of temperature-dependent electrical relaxation phenomena in the material. The values of activation energy were determined from the Arrhenius plot of DC conductivity versus 10³/T and were equal to ~0.09 eV at 50–200°C and ~0.48 eV at 200–350°C. Complex modulus study indicates non-Debye type (polydispersive) conductivity relaxation in the compound.

Manganese doped derivatives of polycrystalline Na_1.89 Li_0.10K_0.01Ti₃O₇ bearing 0.01, 0.05 and 1.0 molar % of manganese have been prepared by chemical synthesis. The results of ac electrical conductivity studies in form of log(σT) versus 1000/T plots are reported in the frequency and temperature range of 10 kHz–1 MHz and 350–775 K, respectively. The corresponding plots have been divided into five temperature regions, I, II, III, IV and V. The various conduction mechanisms in different regions have been discussed. The nature of conductivity has been explained by proposing a model about the obtained conductivity σ(ω) which is the sum of three terms arising from three different mechanisms. Moreover, various Na–K–Li–O–Ti–O linkages in Na_2-x-yLi_x K_yTi₃O₇ materials may result special forms of electron clouds. Experimental results of the loss tangent ( tan δ) and relative permittivity (ε_r) versus temperature at different frequencies have been described. The results of tan δ and ε_r versus frequency plots at different temperature have also been given for these doped derivatives.

The thermoelectric properties of LaCo_1-xCu_xO_3-δ ceramics are theoretically analyzed, it is observed that thermoelectric figure of merit ZT ( = S²σT/κ) is maximized by Cu substitution in LaCo_1-xCu_x O_3-δ at x = 0.15. The lattice thermal conductivity (κ_ph) and phonon drag thermoelectric power were estimated by the scattering of phonons with defects, grain boundaries, electrons and phonon umklapp scattering to evaluate the thermoelectric figure of merit ZT. The Mott expression is used to estimate the electron diffusive thermoelectric power using Fermi energy as electron free parameter, shows linear temperature dependence. The electron contribution to thermal conductivity (κ_e) is estimated using temperature-dependent electron relaxation time. We found that Cu substitution increases the phonon scattering with grain boundaries and defects which significantly decrease the thermal conductivity and subsequently increase the thermoelectric power. The present numerical analysis of thermoelectric properties will help in designing more efficient thermoelectric materials for thermoelectric applications.

Ba₄LaTi_0.3Sn_0.7O₁₅ ceramic was prepared through conventional solid state mix oxide route followed by characterization using X-ray diffraction (XRD) and scanning electron microscope (SEM) for phase and microstructural investigation. The dielectric properties at low and microwave frequencies were measured using LCR meter and vector network analyzer. XRD results revealed single phase ceramics and the microstructure was comprised of compact grains with size ranging from 4–12 μm. The lattice parameters refined by the least squares method were a = b = 5.7680(2) Å, c = 11.7491(6) Å, V = 337.81 ų and Z = 1. Optimum properties i.e., ε_r~44.6, Q_uf_o~15, 500 GHz and τ_f~2.05 ppm/°C were achieved for Ba₄LaTi_0.3Sn_0.7 Nb₃O₁₅ ceramic sintered at 1475°C for 4 h.

The new ceramic compounds type BaREBiO₄ (where RE = Sm and Nd) have been reported for the first time. The sample was prepared by solid-state reaction technique. The orthorhombic crystallization with a = 6.429(4) Å, b = 6.536(5) Å, c = 8.648(4) Å for BaSmBiO₄ and a = 6.485(3) Å, b = 6.561(4) Å, c = 8.686(4) Å for BaNdBiO₄ was studied from powder X-ray diffraction studies. The semiconducting nature of the compounds was observed with the energy gap measurement from diffused reflectance spectroscopy (DRS) studies. The paramagnetic nature of the compounds at room temperature and low temperature conditions was identified by magnetization measurements as a function of magnetic fields and temperature. The effective magnetic moment of the samples was found to be 2.126 μ_B and 4.272 μ_B.

Polycrystalline La_0.93Sb_0.07MnO₃ ceramics were synthesized using solid-state reaction method. The samples were sintered at different temperatures ranging from 1100°C to 1200°C. It is observed that microstructural, transport and magnetic properties of La_0.93Sb_0.07MnO₃ compounds strongly depend on sintering temperatures (T_S). With T_S increasing, the degree of lattice distortion has been weakened, the grain size has become larger and grain boundaries have decreased. Furthermore, the resistivity was reduced, and metal–insulator transition temperature was enhanced; the saturation magnetization per unit mass has decreased with T_S increasing. These effects of different T_S on physical properties can be explained by the structure distortion and grain boundary contributions for La_0.93Sb_0.07MnO₃ compounds.

The sol–gel method was developed to synthesize A₅B₅O₁₇-type Na_0.4K_0.6Ca₄Nb₅O₁₇ layered perovskite ceramics, using NaNO₃, KNO₃, CaNO₃⋅4H₂O and NbCl₅ precursors. Samples were calcined at 950°C and sintered at 1200–1350°C. The phase and microstructural analyses of samples were carried out using X-ray diffractometer (XRD) and scanning electron microscope. X-ray diffraction analysis revealed single phase monoclinic symmetry, within the detection limit of in-house XRD facility. Microstructural analysis shows ~ 10 μm elongated rod-like grains. The microwave dielectric properties of the sintered composition at 1300°C were: relative permittivity (ε_r) = 42, quality factor (Q × f₀) = 8270 GHz and temperature coefficient of resonant frequency (τ_f) = -10.1 ppm/°C.

A number of compounds in the ${\mathrm{\text{Ca}}}_{4+x}{\mathrm{\text{La}}}_{2-x}{\mathrm{\text{Ti}}}_{5-x}{\mathrm{\text{Nb}}}_x{\mathrm{\text{O}}}_{17}$ (x = 0–2) series were prepared through a mixed oxide solid-state sintering route. These compounds crystallized into orthorhombic (Pbnm) structure. The relative permittivity $({𝜀}_r)$ and temperature coefficient of resonance frequency $({\tau }_f)$ depended on the polarizability of constituent cations while the quality factor $(Q\times f_o)$ was affected by ordering of cations. These compounds exhibited promising ${𝜀}_r$ (74–90) and $Q\times f_o$ (10208–14116 GHz); however, the observed high ${\tau }_f$ (157–542 ppm/${}^{\circ }$C) requires further investigations to tune it through zero.

Lead-free piezoceramics ($1-x$)Bi${}_{0.5}$(Na${}_{0.80}$K${}_{0.20}{)}_{0.5}$TiO₃–xLiNbO₃ (BNKT–LN) (where $x=0$, 0.025, 0.050 and 0.075mol fraction) were examined for their ferroelectric stability and subsequent modifications. Traditional solid-state reaction techniques were used to create the BNKT–LN piezoceramics, which were then sintered at a temperature of 1200°C. We concentrated on the structural, dielectric, piezoelectric and ferroelectric properties of the BNKT–LN ceramics. The powder X-ray diffraction pattern revealed a single perovskite structure with no secondary phases, as was observed. The temperature-dependent dielectric curves demonstrated that the maximum dielectric constant ($\epsilon$) is present in the pure BNKT sample and diffuses to a low value when the LN concentration rises. SEM confirms the material’s surface shape, and decreasing grain sizes are seen as the LN content rises. The BNKT–LN ceramics’ P–E hysteresis loops demonstrate good ferroelectric characteristics, with a maximum at 20 kV/cm. With an increase in LN concentration, remnant polarization ($P_r$) and coercive field ($E_c$) show a trend of increasing, reducing and then increasing. The maximum value of the piezoelectric coefficient ($d_{33}$) for the combined samples was 147pC/N. As a result, the lead-free ceramic BNKT (BNKT–LN) doped with LN is an auspicious choice for piezoelectric sensor applications.

The phase formation and thermal-induced phase transformation are studied in BaTiO₃ nanoparticles. 2 h of heating a polymer precursor at 550°C in air formed a single phase BaTiO₃ of 15 nm average crystallite size D. The X-ray diffraction peaks are analyzed assuming a P_nma orthorhombic (o) crystal structure of lattice parameters a = 0.6435 nm, b = 0.5306 nm, and c = 0.8854 nm. The lattice volume V = 0.3023 nm³, with z = 4 formula units, yields a density ρ = 5.124 g/cm³. This is a new polymorph in comparison to well-known P_m3m tetragonal (t) structure, V = 0.0644 nm³ or ρ = 6.016 g/cm³ (z = 1). An o ↦ t transformation appears on heating at temperature as high as 650°C in air. A proposed model explains the transformation above a certain D value in terms of the Gibbs free energy. Unless heating above 750°C, the two phases coexist in a composite structure (D≤27 nm), with as much residual o-phase trace as ~28 vol%. As a function of temperature both the phases decrease in the V values up to 0.2975 and 0.0643 nm³ at 750°C respectively (0.0650 nm³ at 650°C). This is an important parameter for designing useful ferroelectric and other properties in a hybrid composite structure.