The solid solution limit of Ba1-x PbxTiO3 was determined in the composition range of 0≤x≤1.0. All solid solution compounds were indexed in tetragonal symmetry with lead titanate structure type at room temperature. The cell parameters of Ba1-x PbxTiO3 continuously, but nonlinearly, change with x. The structure of Ba1-x PbxTiO3 is tetragonal in the temperature range RT–330℃ and in cubic system beyond 330℃ with HTXRPD. The intrinsic thermal expansion coefficients of Ba1-xPbxTiO3 (x=0, 0.5, 1.0) were obtained. The correlation between thermal expansion and ferroelectric properties is briefly discussed.

The solid solution limit of Pb1−x(La1/2K1/2)xTiO3 was determined in the composition range of 0 ≤ x < 1. The compounds of Pb1−x(La1/2K1/2)xTiO3 were indexed in a tetragonal system for 0 ≤ x ≤ 0.4 and indexed in a cubic one for 0.45 ≤ x < 1 at room temperature. A tiny amount of La2Ti2O7 pyrochlore phase was detected in the sample Pb1−x(La1/2K1/2)xTiO3 for x=1.0. The lattice parameters of Pb1−x(La1/2K1/2)xTiO3 (x=0.1, 0.2, 0.3, 0.4, 0.6, 0.8) were determined by high temperature XRD, and their intrinsic thermal expansion coefficients were obtained in the temperature range from room temperature to 900℃. In the temperature range from room temperature to the Curie point, the compound Pb0.8(La1/2K1/2)0.2TiO3 has a low intrinsic thermal expansion coefficient (−7.1×10−6℃−1), which is the value closest to zero in all the investigated compounds. The (ferroelectric) Curie temperatures of Pb1−x(La1/2K1/2)xTiO3 could be predicted from our experimental results for 0≤x≤0.4.

Lattice parameters of lead titanate were precisely re-determined in the temperature range of −150-950℃ by high precision XRPD measurements. It was clarified that there was no any evidence for a new phase transition at low temperatures. Tetragonal distortion strain decreases with temperature increasing. A novel thermal expansion was observed, positive thermal expansion from −150℃ to room temperature (RT) and above 490℃, and the negative thermal expansion in the temperature range of RT-490℃. A big jump of thermal expansion coefficient is attributed to the tetragonal-cubic phase transition. A rationalization for the negative thermal expansion of PbTiO3 is due to the decrease of anion-anion repulsion as polyhedra become more regular at heating. The mechanisms of positive and negative thermal expansions were elucidated as the same nature in the homogenous tetragonal phase at present case.

The main phase ZrV2O7 material, doped with zirconia and vanadium (V) oxide, was synthesized by solid state reaction and sol-gel methods. X-ray power diffraction patterns show that it is cubic structure. Thermal mechanic analysis measurements present a zero-thermal expansion of this material above 150℃. As well the heat capacity dependent on temperature, determined by differential scanning calorimetry, keeps in constant almost in the same temperature range. The relation between unusual thermal expansion and abnormal heat capacity is discussed with quantum mechanics.