An electric furnace, inside which desired temperatures are kept constant by generating heat, is known to be a difficult system to control and model exactly because system parameters and response delay time are varied as the temperature and position are changed. In this study, the heating system of ceramic drying furnaces with time-varying parameters is mathematically modeled and control parameters are estimated by using a recursive least-square method. The generalized predictive control with exponential weight (GPCEW), which always guarantees the stability of closed loop systems and can be effectively applied to internally unstable systems, is employed in the temperature control of ceramic drying electric furnaces and its performances is experimentally verified. It is proven that temperature tracking of GPCEW is more stable than the generalized predictive control (GPC) and rapidly settles down by increasing the prediction horizon.

The XRD patterns of zinc gallate (ZnGa2O4) thin film phosphors, deposited on indium tin oxide (ITO) glass substrates and glass plates using a chemical solution method, indicated that the annealing temperature was a major factor in controlling the crystallization behavior. Thin films of ZnGa2O4, deposited on the two different substrates, showed the (222), (400), (511) and (440) peaks of the spinel structure as well as the (311) peak indicating a standard powder diffraction pattern. It was also suggested that the presence of the (311) peak of the ZnGa2O4 film phosphor, annealed at 600 °C, could be correlated with embossed morphologies showing surface dots with a regular spacing. Meanwhile, all the ZnGa2O4 thin film phosphors on ITO glass exhibited blue emission spectra in the wavelength range of 400 nm to 445 nm. In particular, ultraviolet (UV) emission near 363 nm was detected in the case of the phosphor film annealed at 500 °C. It seems that the photoluminescence characteristics of the ZnGa2O4 thin film phosphors are influenced by the crystallization behavior during the annealing process.