Strontium and Yttrium-doped and co-doped BaTiO₃ (BT) ceramics with the stoichiometric formulas BaTiO₃, B_1-xSr_xTiO₃, Ba_1-xY_xTiO₃, BaTi_1-xY_xO₃, Ba_1-xY_xTi_1-xY_xO₃, and Ba_1-xSr_xTi_1-xY_xO₃ (x = 0.075) noted as BT, BSrT, BYT, BTY, BYTY, and BSrTY have been synthesized through sol-gel method. X-ray diffraction (XRD) patterns of the prepared ceramics, calcined at a slightly low temperature (950 °C/3h), displayed that BT, BSrT, and BYT ceramics possess tetragonal structures and BTY, BYTY, and BSrTY have a cubic structure. The incorporation of the Ba and/or Ti sites by Sr²⁺ and Y³⁺ ions in the lattice of BaTiO₃ ceramic and the behaviors of the crystalline characteristics in terms of the Y and Sr dopant were described in detail. The scanning electron microscopy (SEM) images demonstrated that the densification and grain size were strongly related to Sr and Y elements. UV–visible spectroscopy was used to study the optical behavior of the as-prepared ceramic samples and revealed that Sr and Y dopants reduce the optical band gap energy to 2.74 eV for the BSrTY compound. The outcomes also demonstrated that the levels of Urbach energy are indicative of the created disorder following the inclusion of Yttrium. The measurements of the thermal conductivity indicated the influence of the doping mechanism on the thermal conductivity results of the synthesized samples. Indeed, the thermal conductivity of BaTiO₃ is decreased with Sr and Y dopants and found to be in the range of 085–2.23 W.m^-1. K⁻¹ at room temperature and decreases slightly with increasing temperature from 2.02 to 0.73-W.m^-1. K⁻¹. Moreover, the microstructure and grains distribution of the BT, BSrT, BYT, BTY, BYTY, and BSrTY samples impacted the compressive strength, hence; the compressive strength was minimized as the grain size decreased.

Porous mullite-based ceramics have been developed using a mixture of zeolite-poor rock and alumina through mechanical activation and reactive sintering. The experimental findings demonstrate that the in-situ mullite growth may develop in a variety of shapes, including whiskers, nanofiber, nanonetwork and diamond-like particles. The XRD examination indicates that the samples sintered at 1500 °C are mostly made of the mullite phase. The SEM photographs show that as the sintering temperature increases, the mullitization process takes place first in zeolite-poor rock particles, and subsequently, alumina combines with the silica-containing phase via a liquid-phase sintering mechanism to produce an interlocking network of extended secondary mullite. The effects of mullite formation and the sintering temperature on various properties of the sintered samples, such as their density, apparent porosity, thermal conductivity, strength, wear resistance, composition, morphologies, and microstructural characteristics of the sintered samples were studied. Increasing the sintering temperature from 1100 to 1500 °C improved the different properties. The density increased from 1.9 to 2.1 g/cm³, thermal conductivity rose from 0.9 to 1.6 W/m.K, compressive strength escalated from 18.9 to 92.1 MPa, and worn material volume decreased from 2444 to 36.9 mm³ after a 5-min abrasion test.