The electrical conductivity of single crystals of rutile was measured in the “c” and “a” directions over the temperature range 1000°–1500°C and from 1 to 10−15 atm of oxygen. Based on the excellent fit observed between the theoretically derived relation σ5=false(Aσ+Bfalse)Pnormalo2−1+I′ σ3 and the experimental conductivity data, the nonstoichiometric defect structure of rutile was rationalized in terms of quasi‐free electrons and both triply and quadruply ionized titanium interstitials. In addition, this equation satisfies a contribution due to impurity conduction where I′ is proportional to a temperature dependent concentration of ionized impurities or a contribution due to intrinsic conduction where I′ is proportional to a temperature dependent concentration of holes in the valance band.The standard enthalpy of formation for the following defect reactions in rutile normalTi+2O=O2false(normalgfalse)+Tii+3+3e;normalΔHao=9.6±0.2 normalev false(afalse) normalTi+2O=O2false(normalgfalse)+Tii+4+4e;normalΔHbo=10.8±0.2 normalevfalse(bfalse) Tii+3=Tii+4+e;normalΔHco=1.2±0.4 normalevfalse(cfalse) I=I++e;normalΔHdo=3.7±0.2 normalev false(dfalse) were determined from the temperature dependence of A , B , and I′ obtained from the above relation and from the experimental expression for the temperature dependence of electron mobility. The values of normalΔHao , normalΔHbo , and normalΔHco are in agreement, within experimental error, with those obtained in an earlier investigation based on conductivity measurements in the c direction only. If impurity conduction is involved, normalΔHdo is equal to the standard enthalpy of formation for the ionization of an impurity. If intrinsic conduction is involved, normalΔHdo is equal to the band gap energy which is thought to be between 3 and 4 ev for rutile. The ratio of electrical conductivities for the c and a direction is essentially independent of oxygen pressure above 1100°C; but at the lower temperatures, 1000° and 1100°C, the ratio is dependent on pressure in contradiction to the initial assumption that mobility is a function of temperature only.

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Tricalcium phosphate ceramic of hydroxyapatite structure with 50% porosity and 800- to 1000-mum pore diameter was implanted in surgically produced infrabony defects in dogs. The defects were evaluated histologically at different time intervals, 1, 2, 4, 8, 16, and 24 weeks. The results show that the ceramic is well tolerated by the tissue and yields no toxic reactions. Bone ingrowth into the pores and repair of the periodontium are clearly demonstrated. No significant hematological changes were observed.

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Potassium hydroxide and sodium hydroxide were found to be satisfactory for polishing various surfaces of rutile. Dislocation etch pits could be produced by alkali fusions, SS% orthophosphoric acid, and concentrated sulfuric acid. The { llO}-, near { 11 1 ) -, (001)-, and { 100) -type surfaces were etched and the etch pits were analyzed in terms of their relation to the deformation systems and crystal symmetry. The correlation between etch pits and dislocations was substantiated by means of matched cleavage surfaces, existence of substructures, generation of dislocations, dislocation densities, and polygonization phenomena. Dislocations were introduced by impacting and macroscopic plastic deformation. Generation of dislocations was observed from 1050°C to as low as room temperature. The slip planes confirmed by means of dislocation traces and slip lines were { 110 ) -and { 101 ]-type planes. The slip direction corresponding to the { 110) -type plane was [OOl 1, the close-packed direction. The Burgers vector, structure, and motion of dislocations in the edge orientation on the { 110) [OOl] system were determined by analyzing the crystal structure. The Burgers vector was c [OOl 1, the lattice translation vector, and the dislocations did not dissociate into partial dislocations. Another possible slip system was the (100) [OlO] system.