TECHNOLOGY FOCUS - CERAMICS AND GLASS - Preferred Components: The substrate comprises a ceramic such as alumina, aluminum oxide, zirconia, zirconium oxide, magnesium oxide, spinel, silicon oxide (SiO2), silicon carbide (SiC), silicon nitride (Si3N4), mullite, and/or quartz.Preferred Process: The coated substrate is sintered in air, nitrogen, hydrogen, or argon atmospheres.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The magnesium oxide-based layer further comprises a dopant such as cobalt oxide, nickel oxide, zirconium oxide, cerium oxide, titanium oxide, iron-oxide, or aluminum oxide. The dopant comprises a concentration of 0-20 mol.%, and has a particle size of 1 nm to 10 microns. The magnesium oxide-base layer is stable at 1-1300degreesC. The magnesium oxide-based layer comprises a top coat providing a hermetic seal; and at least one intermediate coat, subjacent the top coat, comprising magnesium oxide. The top coat comprises cerium oxide-doped magnesium oxide, yttrium oxide -doped magnesium oxide, aluminum oxide -doped magnesium oxide, zirconium oxide-doped magnesium oxide, iron oxide-doped magnesium oxide, nickel oxide-doped magnesium oxide, titanium oxide-doped magnesium oxide, or magnesium oxide. The intermediate coat comprises a first intermediate coat comprising magnesium oxide nano-particles; and a second intermediate coat, substantially subjacent the first intermediate coat, comprising magnesium oxide micro-particles. The magnesium oxide-based layer comprises a depth of 1-200 (preferably 10-20) microns. The bond layer is lanthanum oxide-doped magnesium oxide, cerium oxide-doped magnesium oxide, titanium oxide-doped magnesium oxide, cerium oxide, iron oxide, nickel oxide, copper oxide, magnesium oxide, titanium oxide, aluminum oxide, nickel oxide-doped magnesium oxide, zirconium oxide-doped magnesium oxide, cerium oxide-doped magnesium oxide, aluminum oxide-doped magnesium oxide, nickel-doped magnesium oxide, zirconium oxide, iron oxide-doped magnesium oxide, copper oxide-doped magnesium oxide, or strontium oxide-doped magnesium oxide. The bond layer further comprises a binding agent and/or a surfactant.    TECHNOLOGY FOCUS - METALLURGY - Preferred Components: The substrate comprises a metal such as ferrous metal, non-ferrous metal, stainless steel, metal alloy, metal superalloy, or Haynes 230 (RTM: superalloy). The metal substrate comprises a chemical-etched bonding surface, roughened bonding surface, sand-blasted bonding surface, and/or pre-oxidized bonding surface; or a surface prepared by chemically cleaning and ultrasonification.